BARRIER TO MOISTURE VAPOUR TRANSFER THROUGH THE SURFACE OF

A MATERIAL AND/OR FOR REMOVING MOISTURE FROM A MATERIAL

Technical Field This invention relates to a process of and apparatus for providing at least a partial barrier to moisture vapour transfer through the surface of a material without substantially spoiling the material, a process of and apparatus for removing moisture from a material without substantially spoiling the material, and a process of and apparatus for providing at least a partial barrier to moisture vapour transfer through the surface of a material and for removing moisture trom the material without substantially spoiling the material.

Background of the Present Invention

In the snack food and home microwaveable prepared food sectors of the food processing industry are of major world wide economic importance and are rapidly expanding in response to the demand of community changing lifestyles. However, the nutritional and diet value of many of such products and in particular snack foods is widely criticised and is the subject of increasing public concern and market awareness. A major reason for the low nutritional quality of many of the products in the snack food sector is due to the production difficulties which are experienced in the processing of many of the wholesome, basic food products, such as for example, cheeses, meats, fruits, vegetables and berries, into high quality, long shelf life, nutritious, non-chewy, flavoursome products having consumer appeal. Of the many basic food products affected in this manner, cheese is one of the most important due to its availability for processing on a year round basis and because of its high nutritional and energy properties and important contribution to balanced tood diets. As a consequence of these processing difficulties, many of the cheese snack products in the market are bland and of poor nutritional value and lack customer appeal. These products often consist of a cereal or similar core material finished in a cheese flavouring or cheese coating. The processed quality of other dried snack tood products, such as for example, meats, fruits, vegetables and berries which could be considered as nutritious additives to cheese based snack food products are themselves typically characterised after processing as having tough skins, chewy texture and bland taste devoid of any

significant distinguishing flavour or taste Some processes used in the cooking ot foods, and particularly tor example that relating to boiling, stewing, baking, leavening, frying, grilling and toasting have been observed and practised tor centuries

Notwithstanding the development ot the industrial tood processing industry and the introduction ot more sophisticated cooking and drying methods and the advent ot microwave heating, the tood cooking and tood processing methods and technologies and operating techniques in use today still remain more ot an art than an inventive science It is known that the processing ot cheeses, fruits, meats, vegetables, spices and other agricultural produce having a distinctive taste, texture and aroma, by the use of conventional heating, cooking and drying technologies and methods and processes such as convection ovens, hot air cooking and drying systems radiant heating and conductance heating systems, all cause changes to the surface properties of the product and volatilise to a greater or lesser degree the low molecular weight compounds which give rise to much ot the distinctive properties ot the fresh product It is apparent that there is a need tor a processes tor ot removing moisture from a material without substantially spoiling the material

Object of Invention

Objects of the invention are to provide a process ot and apparatus for providing at least a partial barrier to moisture vapour transfer through the surface ot a material without substantially spoiling the material, a process ot and apparatus tor removing moisture from a material without substantially spoiling the material, and a process ot and apparatus tor providing at least a partial barrier to moisture vapour transfer through the surface ot a material and tor removing moisture trom the material without substantially spoiling the material Disclosure of Invention

According to a first embodiment ot this invention there is provided a process of providing at least a partial barrier to moisture vapour transfer through the surface ot a material without substantially spoiling the material, said process comprising

(A) sub _j ecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure ot water which do not spoil the material, and, in which the partial vapour pressure of water ot said environment is below saturation.

(B) irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without spoiling the material; and (C) maintaining (i) the temperature of the environment, and, (n) the partial vapour pressure of water of said environment below saturation, whereby the material whereby the material is not spoilt during step (B).

According lo a second embodiment of this invention there is provided a process for removing moisture from a material without substantially spoiling the material, said process comprising:

(a) subjecting the material to a controlled humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure ol water ot said environment is below saturation; (b) irradiating the material in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the vapour pressure at the surface is greater than the vapour pressure of the environment whereby moisture is transferred from the surface to the environment, wherein the amount of said microwave irradiation is not sufficient to spoil the material; and (c) maintaining (i) the temperature of the environment, and, (n) the partial vapour pressure of water of said environment below saturation, whereby the material is not spoiled during step (b); said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature of the material more than 50% of the wet bulb depression of the environment.

According to a third embodiment of this invention there is provided a process of providing at least a partial barrier to moisture vapour transfer through the surface of a material and for removing moisture from the material without substantially spoiling the material, said process comprising. providing at least a partial barrier to moisture vapour transfer through the surface of a material without substantially spoiling the material, said process comprising-

(A) subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation; (B) irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without spoiling the material; and

(C) maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment below saturation, whereby the material whereby the material is not spoilt during step (B); and removing moisture from a material without substantially spoiling the material, said process comprising:

(a) subjecting the material to a controlled humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation;

(b) irradiating the material in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the vapour pressure at the surface is greater than the vapour pressure of the environment whereby moisture is transferred from the surface to the environment, wherein the amount of said microwave irradiation is not sufficient to spoil the material; and

(c) maintaining (i) the temperature of the environment, and. (ii) the partial vapour pressure of water of said environment below saturation, whereby the material is not spoiled during step (b); said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature of the material more than 50% of the wet bulb depression of the environment. Advantageously in the process of the first or third embodiments step (B) comprises:

(B) simultaneously or sequentially irradiating the material in the environment with infra red radiation and microwave irradiation, said amount ot infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without spoiling the material, and said amount of microwave irradiation being sufficient to cause a slight positive vapour pressure within the material to prevent the material trom deflating, wherein the amount of said microwave irradiation is not sufficient to spoil the material.

Typically in the process of the first or third embodiments step (A) comprises:

(A) subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a said environment being at a pressure which does not spoil the material.

Typically in the process of the second or third embodiments- said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature of the material more than 30% of the wet bulb depression of the environment.

More typically in the process of the second or third embodiments: said amount of microwave irradiation is sufficient to substantially maintain said vapour pressure at the surface, until a required amount ol moisture has been removed from said material, without substantial reduction of the surface temperature of the material.

Typically in the process of the second or third embodiments step (a) comprises:

(a) subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and. in which the partial vapour pressure of water of said environment is below aturation;

More typically in the process of the second or third embodiments step (a) comprises:

(a) subjecting the material to a controlled pressure and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and. in which the partial vapour pressure of water of said environment is below saturation

Even more typically in the process of the second or third embodiments step (a) comprises:

(a) subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation.

Typically in the process of the second or third embodiments in step (b) the temperature of the surface of the material is substantially the same as the dry bulb temperature of the environment. According to another embodiment of this invention there is provided a process of providing at least a partial barrier to moisture vapour transfer through the surface of a material without substantially spoiling the material , said process comprising:

(A) subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation;

(B) irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without burning, cooking, or causing surface damage to the material so as to spoil the material; and

(C) simultaneously maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment below saturation, whereby the material does not burn, cook or incur surface damage during step (B) so as to spoil the material.

Typically step (B) comprises:

(B) simultaneously or sequentially irradiating the material in the environment with infra red radiation and microwave irradiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without burning, cooking, or causing surface damage to the material so as to spoil the material, and said amount of microwave irradiation being sufficient to cause a slight positive vapour

pressure within the material to prevent the material from deflating, wherein the amount of said microwave irradiation is not sufficient to remove a substantial amount of moisture from the material , burn, cook, or cause surface damage to the material so as to spoil the material . The material may be irradiated sequentially once or a plurality of times, e.g. 2- 10,000, more typically 2 to 5,000, even more typically 2 to 1 ,000, yet even more typically 2- 100 and even more typically 2 to 10 (or even more typically 2 to 50, 2 to 25, 5 to 10 times).

Typically in the step (A) comprises: (A) subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation.

According to a further embodiment of this invention there is provided a process for removing moisture from a material without substantially spoiling the material, said process comprising:

(a) subjecting the material to a controlled humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation; (b) irradiating the material in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the vapour pressure at the surface is greater than the vapour pressure of the environment whereby moisture is transferred from the surface to the environment, wherein the amount of said microwave irradiation is not sufficient to spoil the material; and (c) simultaneously maintaining (1) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment below saturation, whereby the material is not spoiled during irradiation of the material in the environment with microwave irradiation; said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature of the material more than 50% of the wet bulb depression of the environment

Typically said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material , without reducing the surface temperature of the material more than 30% of the wet bulb depression of the environment.

More typically, said amount of microwave irradiation is sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material , without substantial reduction of the surface temperature of the material.

Even more typically the surface temperature of the material is reduced from a% to b% of the wet bulb depression of the environment where a is selected from the group consisting of a value presented in the column headed "a" in Table A ¹ " below at one of entries 1 -20, and b is selected from the group of the values presented in the column headed "b" adjacent the corresponding "a" entry.

Table A*

Typically step (a) comprises:

(a) subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation.

Step (a) may comprise:

(a) subjecting the material to a controlled pressure and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation.

Step (a) may comprise:

(a) subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and. in which the partial vapour pressure of water of said environment is below saturation.

Typically the temperature of the surface of the material is substantially the same as the dry bulb temperature of the environment.

Typically step (A) is preceded by:

(I) preparing the material in a suitable form for processing by the process of the first or third embodiments; and

(II) heating or cooling the material of (I) to a preselected temperature said temperature being less than that which would spoil the material and being equal to or less than the temperature of step (A).

Typically step (a) is preceded by:

(I) preparing the material in a suitable form for processing by the process of the second embodiment; and

(II) heating or cooling the material of (1) to a preselected temperature said temperature being less than that which would spoil the material and being equal to or less than the temperature of step (a).

Typically step (c) is followed by:

(1 ) optionally cooling the material;

(2) sterilising the material; and (3) optionally packaging the material.

In the preferred form a microwave sterilisation process is combined with packaging by the use of microwaveable packaging materials suitable for stable long shelf life food products. In another preferred process the sterilisation process is carried out as part of step (c) followed by a cooling process if required prior to packaging in controlled atmosphere packaging materials commonly used in the food packaging industry. According to another aspect of the invention there is provided as an integral part of the method of production a process for end product sterilisation by microwave radiation. In the preferred embodiment in the invention the sterilisation stage is carried out as an integral part of the final production stage immediately prior to packaging but sterilisation can equally be carried out as an integral part of the product packaging stage by the use of microwaveable long shelf life packaging materials in common use in the industry.

According to a preferred form of the invention there is provided a process of production incorporating the preferred process stages of: (a) starting material preparation and process presentation delivery stage;

(b) An initial processing stage in which the presented starting material is processed under a controlled temperature and pressure environment (atmospheric or vacuum) using a combination of infra-red radiant heating and microwave irradiation and vapour extraction/condensing closed cycle heat pump drying and controlled product temperature;

(c) A final cooking/drying/puffing/foaming/processing stage as applicable to meet the end product specifications and incorporating continuously variable product feed back controlled microwave irradiation in a temperature and pressure controlled (atmospheric or sub-atmospheric) environment complete with vapour extraction/condensing system and emission control;

(d) Product microwave sterilisation and packaging and cooling stage.

According to a fourth embodiment of this invention there is provided an apparatus for providing at least a partial barrier to moisture vapour transfer through the surface of a material without substantially spoiling the material, said apparatus comprising: (A) means for subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material , and. in which the partial vapour pressure of water of said environment is below saturation;

(B) means for irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without spoiling the material; and

(C) means for maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment below saturation, whereby the material whereby the material is not spoiled.

According to a fifth embodiment of this invention there is provided an apparatus for removing moisture from a material without substantially spoiling the material, said apparatus comprising:

(a) means for subjecting the material to a controlled humidity environment, said environment being al a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation;

(b) means tor irradiating the material in the environment with an amount ot microwave irradiation effective to increase the moisture at the surface ot the material whereby the vapour pressure at the surface is gi eater than the vapour pressure ot the environment whereby moisture is transferred trom the surface to the environment, wherein the amount ot said microw av e irradiation is not suf ficient to spoil the material , and

(c) means tor maintaining (1 ) the temperature ot the environment, and, (n ) the partial vapour pressure ot water ot said environment below saturation, whereby the material is not spoiled, said amount ot microwave irradiation being suf f icient to substantially maintain said vapour pressure at the surface, until a required amount ot moisture has been removed trom said material, without reducing the surlace temperaiuie ot the material more than 50% of the wet bulb depression ot the environment

According to a sixth embodiment ot this invention there is provided an apparatus for providing at least a partial barrier to moisture vapour transfer through the surface of a material and for removing moisture trom the material without substantially spoiling the material , said apparatus comprising in combination an apparatus for providing at least a partial barrier to moisture vapour transfer through the surface of a material without substantially spoiling the material , said apparatus tor providing at least a partial barrier it) moisture vapour transfer comprising

(A) means tor sub|ectmg the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material , and, in w hich the partial vapour pressure of water of said environment is below saturation. (B) means tor irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier lo moisture v apour transfer through the surface of the material without spoiling the material, and

(C) means tor maintaining (i ) the temperature ot the environment, and, (n) the partial vapour pressure ot water ot said environment below saturation, whereby the material whereby the material is not spoiled, and

π apparatus tor removing moisture trom a material without substantially spoiling the material, said apparatus tor removing moisture comprising

(a) means tor subiecting the material to a controlled humidity environment, said environment being at a temperature and partial v apour pressure ot water which do not spoil the material, and, in which the partial vapour pressure ot water ot said environment is below saturation.

(b) means tor irradiating the material in the environment with an amount ot microwave irradiation effective to increase the moisture at the surface ot the material whereby the vapour pressure at the surface is greater than the vapour pressure ot the environment whereby moisluie is transferred t rom the surface lo the environment, wherein the amount ot said microwave irradiation is not sufficient to spoil the material, and

(c) means tor maintaining (i) the temperature ot the environment, and, (n) the partial vapour pressure of water ot said environment below saturation, whereby the material is not spoiled, said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount ot moisture has been removed from said material, without reducing the surface temperature of the material more than 50% ot the wet bulb depression ot the environment Advantageously in the apparatus ot fourth or sixth embodiments (B) comprises

(B) means tor simultaneously or sequentially irradiating the material in the environment with tra red radiation and microwave irradiation, said amount ot infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without spoiling the material, and said amount ot microwave irradiation being sufficient to cause a slight positive vapour pressure within the material to prevent the material trom deflating, wherein the amount ot said microwave irradiation is not sufficient to spoil the material Typically in the apparatus of fourth or sixth embodiments (A) comprises (A) means tor subiecting the material to a controlled pressure, temperature and humidity environment, said enviionment being at a said environment being at a pressure which does not spoil the material

Typically in the apparatus of fifth or sixth embodiments (a) comprises

(a) means tor subiecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and. in which the partial vapour pressure ot water ot said environment is below saturation.

Typically in the apparatus ot fifth or sixth embodiments (a) comprises

(a) means for subiecting the material to a controlled pressure and humidity environment, said environment being at a pressure, temperature and partial vapour pressure ot water which do not spoil the material, and. in which the partial vapour pressure of water ot said environment is below saturation

Typically in the apparatus ot fifth or sixth embodiments (a) comprises-

(a) means tor subiecting the material to a controlled pressure, temperature and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure ot water ot said environment is below saturation.

According to another embodiment ot this inveniion there is provided an apparatus for providing at least a partial barπei to moisture vapoui transfer through the surface of a material without substantially spoiling the material, said apparatus comprising:

(A) means tor subiecting the material to a controlled temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation;

(B) means tor irradiating the material in the environment with infra red radiation, said amount of infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without burning, cooking, or causing surface damage to the material so as to spoil the material: and

(C) means tor simultaneously maintaining ( I ) the temperature of the environment, and, (n) the partial vapour pressure ot waier ot said environment below saturation, whereby the material is not burnt cooketl or surface damaged during irradiation of the material in the environment with infra red radiation so as to spoil the material, said

means for irradiating the material in the environment with infra red radiation being operatively associated with said means toi simultaneously maintaining (1) the temperature ot the environment, άn , (n) partial v apour pressure ot water ot said environment below saturation whereby the material is not burnt cooked or surface damaged during irradiation ot the material in the environment with infra red radiation so as to spoil the material .

Typically (B) and (C) comprise

(B) means for simultaneously or sequentially irradiating the material in the environment with infra red radiation and microwave irradiation, said amount ot infra red radiation being sufficient to at least partially seal the surface ot the material to provide at least a partial barrier to moisture vapour transfer through the surface of the material without burning, cooking, or causing surface damage to the material so as to spoil the material, and said amount ot microwave irradiation being sufficient to cause a slight positive vapour pressure within the material to prevent the material from deflating, wherein the amount of said microwave irradiation is not sufficient to substantially remove moisture Irom the material, burn, cook, or cause surface damage to the material so as to spoil the material, and

(C) means for simultaneously maintaining (i) the temperature of the environment, and, (n) the partial vapour pressure ot water ot said environment below saturation, whereby the material does not burn. cook, or experience surface damage so as to spoil the material during simultaneous irradiation of the material in the environment with infra red radiation and microwave irradiation, said means for simultaneously or sequentially irradiating the material in the environment with infra red radiation and microwave irradiation being operatively associated with said means for simultaneously maintaining (l) the temperature of the environment. (n) the partial vapour pressure of water of said environment below saturation, whereby the material does not burn, cook, or experience surface damage so as to spoil the material during simultaneous irradiation of the material in the environment w ith infra red radiation and microwave irradiation. Typically (A) comprises:

(A) means for subiecting the material to a controlled pressure, temperature and humidity environment, said env ironment being at a temperature which is less than that

which would spoil the material, and. in w hich the partial vapour pressure of water of said environment is below saturation.

According to a further embodiment of this invention there is provided an apparatus for removing moisture from a material without substantially spoiling the material , said apparatus comprising:

(a) means for subjecting the material to a controlled humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation; (b) means for irradiating the material in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the vapour pressure at the surface is greater than the vapour pressure of the environment w hereby moisture is transferred from the surface to the environment, wherein the amount of said microwave irradiation is not sufficient to spoil the material; and

(c) means for simultaneously maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment below saturation whereby the material is not spoilt during irradiation of the material in the environment with microwave irradiation, said means for irradiating the material being operatively associated with said means for simultaneously maintaining ( I ) the temperature of the environment, and, (ii) the partial vapour pressure ..■( water of said environment below saturation whereby the material is not spoilt during irradiation of the material in the environment with microwave irradiation; said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount \ moisture has been removed from said material, without reducing the surface temperature of the material more than 50% of the wet bulb depression of the environment.

Typically said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature of the material more than 30% of the wet bulb depression of the environment.

More typically , said amount of mici owav e n i adiation is sutticient 10 substantially maintain said vapour pressure at the surlace. until a required amount ot moisture has been removed trom said material, w ithout substantial reduction ot the surface temperature ot the material Even more typically the surlace temperature ot the material is reduced from a% to b% ot the wet bulb depression ot the environment where a is selected trom the group consisting ot a value presented in the column headed "a" in Table A above at one ot entries 1-20, and b is selected trom the group ot the values presented in the column headed "b" ad|acent the corresponding "a" entr\ Typically (a) comprises

(a) means tor subiecting the maienal lo a contiolled temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material and. in w hich the pai tial v apour pressure ot water ot said environment is below saturation More typically (a) may comprise

(a) means tor subiecting the material to a controlled piessure and humidity environment, said environment being at a temperature which is less than that which would spoil the material , and. in which the partial vapour pressure ot water of said environment is below saturation Typically (a) comprises

(a) means tor subiecting the material lo a controlled pressure, temperature and humidity environment, said environment being at a temperature which is less than that which would spoil the material, and, in which the partial vapour pressure ot water of said environment is below saturation Typically the temperature ot the surface ot the material is substantially the same as the dry bulb temperature ot the environment

Typically (A) includes or in addition to (A) there is

(I) means lot preparing the material in a suitable form tor processing; and

(II) means for heating or cooling the material ot (I) to a preselected temperature said temperature being less than that which would spoil the material and being equal to or less than the temperature ot (A)

Typically (a) includes or in addition to (a) theie is

(I) means tor preparing the material in a suitable form toi processing, and

(II) heating 01 cooling the material ot (I ) to a preselected temperature said temperature being less than that which would spoil the material and being equal to or less than the temperature ot (a)

Typically (c) includes or in addition to (c) there is

( 1 ) optionally means tor cooling the material.

(2) means lor sterilising the material, and

(3) optionally means tor packaging the material In the preferred form a microwave sterilisation process is combined with packaging by the use ot microwaveable packaging materials suitable toi stable long shelf life food products In another preferred process the sterilisation process is carried out as part ot step (c) ot the second or third embodiments lollowed by a cooling process it required prior to packaging in controlled atmosphere packaging materials commonly used in the food packaging industry

The processes ot the invention may be carried out under continuous environmental and product control and do not incorporate convection heating, cooking or baking or any conventionally understood baking process The infra red radiation used in the processes and apparatus of the present invention do not heat the atmosphere through which they pass. For heat transfer they rely on the absorption ot their radiant energy by the surface of the product which is being radiated Intra-red rays have only a very minor penetration through the surface ot most products The heat transfer characteristics and efficiency can be calculated by the application ot recognised engineering formulae

In the methods ot the second and third embodiments and apparatus ot the fifth and sixth embodiments "puffing" of some tood products including cheeses can be achieved by microwave processing without lecourse lo the conv entional baking process and high air temperatures or the use of leavening agents This is due to the tact that suitable internal vapour pressures can be generated within the pioduci by controlling the intensity ot microwave energy and the processing time Further by controlling the temperature of the product by microwave energv, and contiollmg the processing atmosphere temperature, pressure and humidity the putting piocess can be further controlled due to

the surface conditioning of the product It should be noted that in the invention the processing atmosphere will be maintained at a temperature not exceeding the product temperature and no sensible heating energy passes from the air to the product. This is precisely the reverse of convection cooking. Some cheeses require additional "surface conditioning" to increase the extent of puffing. This is typically achieved by an infra-red radiant heating process which again eliminates the need for heating energy to pass from the processing atmosphere into the product as would be the case with convection baking

The use of infra-red radiation in conjunction with microwave processing and integrated temperature control of the product and the processing atmospheric conditions, enables surface conditioning of the product lo be achieved without a "cooking and baking step.

The processing steps defined in the embodiments ot the invention relate to continuous flow processing. The steps are sequential but may be operated in part or in whole sequentially or simultaneously depending on the specific processing application. The processing apparatus of the invention provides for this flexibility of operation.

The inclusion of electro- magnetic infra-red radiant heating in combination with microwaves and the integrated control of product temperature and the processing atmospheric pressure, temperature and humidity in the first embodiment is not a convection heating, cooking or baking step. Using the processes of the invention it is possible in many instances to establish and maintain optimum processing conditions for the repetitious commercial production of high quality snack foods, such as for example, the range of cheese and cheese based products referred to in this invention.

Factors which influence the processing of specific products include: (a) The physical form of the product which is presented for processing, including for example, the unit surface area versus product volume and mass, product consistency, texture, colour and aroma Λ\K\ form and temperature of the presented product and conveying platform characteristics .

(b) The chemical composition of the presented product and the compatibility of the ingredients of a product mixture for simultaneous processing and quality control or otherwise requiring independent pre-treatment.

(c) The environment m which the product is to be processed, for example, in a natural ambient atmospheric pressure environment having no control ot dry bulb and wet bulb temperature or alternatively in a controlled ambient environment in which the dry bulb and wet bulb temperatures are controlled or alternatively in a fully controlled environment in which the dry bulb and wet bulb temperatures and operating pressure is controlled at atmospheric pressure or sub-atmospheric (vacuum) pressure as determined principally by the product temperature sensitivities

(d) The impact of the selected form ot process heating and drying at each stage of the production process, including lor example, the process impact on the surface condition ot the product and Us internal sirucluie, the volatilisation of aromatic compounds and the formation and control ot product puffing and progressive rate of removal ot the product water vapoui and product sterilisation to meet the final product specifications on a continuous process basis. In the processes of the invention the relationship between the process environment temperature and vapour pressure and the product surface temperature and surface vapour pressure is an important relationship and influencing factor in product processing quality control and energy efficiency ot the production process.

Puffing ot products during piocessing. as tor example, in the production ot some cheese products described in this invention, cm be induced and controlled by the process of the invention having regard to such factors as tor example:

(a) the surface area of the presented product with respect to the volume and mass of material contained.

(b) the method and form and physical and chemical properties and ingredients of the material as presented for processing including tor example temperature, viscosity if applicable, containment if any, surface area available for sensible heat transfer and moisture evaporation and starting moisture content

(c) the processing ambient air dry bulb and wet bulb temperatures and operating pressure throughout the manufacturing process (d) the relationship between the piocessing ambient air conditions noted in (c) and the product moisture content and surface temperature and surface vapour pressure throughout the production process

(e) the processing potential for the induced formation of a product surface skin or preferably a light glazing to increase the surface permeability resistance to the transfer or product vapours and hence in one aspect assist in the control of puffing. (f) the respective processing sub-system time/performance profiles and performance characteristics.

Typically the apparatus of the invention includes a surface temperature sensor (e.g. a fibre optic temperature sensing device or an infra red sensing device) to measure the surface temperature of the material. The microwave electromagnetic heating frequencies typically used in the processes of the invention 896. 915. 922 and 2450MHz ± permitted deviations which have been allocated by international agreement for this purpose. More typically the microwave frequency used is in the range 915 ± 25 lo 22. 125 ± 125 megacycles/ econd more typically 915 ± 25 to 7,500 ± 50 megacycles/ second. The preferred frequency is 2450MHz having regard to the process requirements for product penetration, energy intensity capacity, operational control flexibility and high on-line production availability and maintenance.

According to a further aspect of the preferred embodiments of the present invention there is provided a means whereby a microwave energy heating system incorporated in the production process described in the second embodiment is u.sed in whole or in part to control the product internal and surface temperature to a pre-determined processing temperature which may for example be controlled to the wet bulb temperature of the ambient air/vapour or held at the dry bulb temperature of the ambient air/vapour or at any pre-determined surface temperature above the ambient wet bulb temperature but preferably not higher than 100°C and more preferably lower than 80°C and most preferably lower than 60°C.

It should be appreciated that the invention has industrial applicability to a wide variety of food manufacturing processes where the preferred embodiments of the invention may be used in part or in whole or as independent processing sub-systems or as a combination of processes operating sequentially or simultaneously depending on the specific processing application.

In its preferred form for the production of cheese and cheese based products for example, there is provided in the starting material preparation stage fully controllable means for:

(a) receiving hot viscous cheese from a cheese processing cooker or other prior processing plant or storage facility at a temperature in the range 40° to 90°C and preferably in the range 40° to 60°C.

(b) Receiving cold pieces or links of processed or other cheeses or cheese mixtures which have been pre-formed or sliced or diced or cut or pressed to a pre¬ determined size and shape and/or weight relative to the end product specification. (c) The preparation of the starting material into its preferred form for subsequent processing and including for example such preparation processes as grinding, mixing, adding of condiments, emulsifiers. flavours, and other additives in standard proportions in accordance with the recipe of the particular product and blended for uniformity of the starting material for presentation for production processing.

(d) The controlled delivery and presentation tor processing of the prepared starting material for example in extruded viscous cheese form as continuous strips or drops or other shapes or as cold links of processed cheese or other cheeses and cheese mixtures - all to predetermined size, shape and unit weight deposited onto a microwave transparent conveyor bell or other conveying system designed to suit the subsequent processing energy system and the characteristics of the product material and end product specifications and quality control.

(e) In its preferred form the starting material delivery and presentation sub-system described in (d) above there is provided a means for product heating and cooling to enable the temperature of the product to be automatically controlled to an adjustable pre-determined temperature of the product at the point of presentation for processing by the processes of the first and/or second embodiments.

According to a further aspect of the preferred embodiment of the present invention there is provided a means whereby the dry bulb and wet bulb temperatures of the recirculating ambient air/vapour mixture in the product processing chamber in the preferred form of the method of production described in the second embodiment is controllable relative to the surface temperature of the product being processed such that

the drying process is engineered to operate as an adiabatic or isothermal process or at any pre-determined combined process between these two specific conditions.

The processes of the invention are suited to the manufacture of a wide range of food products and in particular snack food products and consumer shelf products and for the processing of agricultural products having similar processing requirements. Examples include snack food products including puffed snack food products and dried products from the following starting materials: All-natural cheeses and processed cheese (which may include other additives uch as carbohydrates, cereals, proteins, meats, fruits, nuts, minerals, vegetables, colouring, flavouring, sodium and non-sodium emulsifiers, condiments, eggs, spices, and smallgoods. and other additives, may be included), including low fat cheeses and cheese based mixtures and including for example all Cheddars, Colby, Swiss processed cheese, condiments, spices, marine algae, marine plants including seaweed, protein sources such as egg protein, soy protein, milk protein, gluten or caseinate which may optionally be emulsified with plant or animal fat or oils such as soybean, sunflower, peanut, olive, canola, safflower or palm oil, together with other components and water, cereals including wheat, rye, corn, rice, millet, sorghum, maize, barley and oats, nuts including peanuts, almonds, cashews, hazel nuts, maccadamia nuts, walnuts, flesh of prawns, shrimps, yabbies, Balmain bugs, pippies, flesh of turtles, flesh of tortoises, eels, octopus, squid, flesh of lobsters, flesh of crayfish, flesh of crabs, marine mammals and fish including hardiheads, white bait, mullet, sardines, salmon, tuna, trout, bream, black fish, flathead, tailer, John Dory, schnapper, trevally, sweep, shark, garfish, pike, leatherjacket, wrasse, mulloway, dolphin fish, kingfish, blennies, gobies, toad fish and other like fish, plant proteins and/or polypeptides from rice, barley, oat. rye. corn, wheat, animal meats and poultry including, beef, chicken, pork, rabbit and turkey, flowering plants such as rose, iris, carnation, daffodil , lily, vegetables such as cabbage, cauliflower, peas, beans, such as soyabeans, lentils, m ng beans, lima beans, kidney beans, adzuki beans, and broad beans, broccoli, brussel sprouts, peanuts, chickpeas, asparagus, soya extracts, natural & processed dairy products, fruits including apples, bananas, apricots, plums, cherries, pears, pineapple, vine products including grapes and dates, fruit skins including orange and mandarin skins, and fruit seeds including grape seeds, berries, herbs & spices raw material , vegetable produce natural &. semi-processed, oil seed, seeds, nodular and granular products, agricultural produce waste products: chemical

compound recovery-citrus fruits, grape waste, paper pulp products, wood chips, wood shavings, sawdust, dehydration of chemical powdei compounds, honey , treacle, sugar cane and molasses including sugar beet process molasses, tor example

The processes of the invention are capable ot processing a wide range ot starting materials which typically are cheese and cheese based mixed products which may vary in moisture content trom 20-60% and in tat content trom 15-559? in dry matter The method of production is not limited to these typical analyses and would satisfactorily process starting materials having highei or lower moisture and tat contents than those indicated, the mam variable in the process being the product residence time. According to another aspect ot the inv ention there is provided a range ot snack food products manufactured trom natuial cheeses oi processed cheeses or cheese based mixed ingredient starting materials and including tor example such ingredients and additives as fruits, vegetables, cereals, berries, nuts, meats, eggs, smallgoods and herbs and spices to provide added flavour and/or nutritional value and variety of products when prepared by a process of the invention.

According to another aspect of the invention there is provided a range of manufactured wholesome cheese based snack tood products characterised by their dry , crisp, crunchy, open cellular properties and high nutritional and energy value and palate appeal when prepared by a process ol the invention By way of example only, these prod tic is include.

(a) A range of cheese based, dry. crisp, crunchy snack tood products tor example in the form of biscuits, crackers anil waters ot various sizes, shapes and flavours, and of full cheese or mixed cheese and other ingredients content.

(b) A range of dry, crisp, crunchy snack food products tor example in the form of snaps, curls, twists, crisps, balls, chips and sticks of various flavours and of full cheese or mixed cheese and other ingredients content.

(c) A range of light putted or foamed snack lood products m the form tor example of cookies, cakes, puffs, buns and loaves ot various flavours and of full cheese or more preferably mixed cheese and othei ingredients content According to another aspect ot the invention there is provided a range of long shelf life snack food products as described above tor example and pre-processed and sterilised

and packaged in microwaveable pac kaging ιead\ toi final home microwave heating tor serving as hot savoury snack loods

According to another aspect ot the invention theie is piovided a range tor example ot stable long s elf lite, dried, ground, packaged and sterilised cheese and cheese based mixed ingredients tor use as flavouring dnύ cooking additives, spiced cheese condiments and cheese fruit and cheese nut additives, fillings and spreads when prepared by a process ot the invention

According to another aspect ot the invention there is provided a process ot the invention in which the moistuie content ot the processed material is dried to a predetermined specification requiremem w hich is determined tor the particular product having regard to shelf lite, stable physical condition and consumer appeal but typically being between 1 5 % 1 ' _Λ I he piocess is not limited lo processing within this range and higher or lower moisture contents are prov ided

Also provided is a process ot production and a process suitable tor the manufacture of vegetable and animal fat and protein based tood products which exhibit similar processing requirements to thai ot the cheese based products covered by this invention

TABLE A: Examples of Types of Product Applications

TABLE B: Expected Maximum Ranges of a Number of Process

Parameters

2^

#For the list of Products corresponding to the Product Designation refer to column 2 of Table C.

TABLE C: Expected Maximum Ranges of a Number of Process

Parameters

\

Step 2: H(2) - Processing environment R - ^r

P(2) - Processing env ironment atmospheric pressure

T(2) - Processing environment DB temperature

T(2) ' -Bulk material temperature T(2)- - Surface temperature material

Step 3: T(3) - Processing environment DB temperature

T(3) ' - Bulk material temperature T(3) ² - Surface lemperaiure of material H(3) - Processing environment RH 9f P(3) - Processing equipment atmospheric pressure

WBD(3) - Processing environment DB temperature minus the processing environment WB lemperaiure.

Note: DB = dry bulb lemperaiure

WB = wet bulb temperature RH % = relative humidity percentage

Temperature = in degrees eel si us Pressure = in relation to one ( I ) atmosphere.

T(0), T( l ). T(2), and T(3) have expected maximum temperature ranges as listed in Table B, and T(2)' . and T(3)' have expecled maximum temperature ranges as listed in Table C. Preferred temperatures or temperature ranges within these expected maximum temperature ranges for each ol these parameters are listed in Table D. Thus to choose a particularly preferred temperature range e ( ^' - PX tor a particular T. e is selected from the group consisting of a value presented in the column headed "e" in Table D below at one or more of entries 1 -25 (where e _ the minimum temperature listed in Table B for the particular T), and f is selected from the group \ ^' the values presented in the column headed "f" adjacent the corresponding "e ^" entry (where f -- the maximum temperature listed in Table B for the particular T).

3

TABLE I ⁾ : Temperature ranges ol Piiπinulers I (0), T(l). T(2), T(3). T(2)', T(3)'

H( l ), H(2), and H(3) have expecled maximum humidity ranges as listed in Table B. Preferred humidities or humidity ranges within these expected maximum humidity ranges for each of these parameters are listed in Table E. Thus to choose a particularly preferred humidity range g% - '/ϊ for a particular H . g is selected from the group consisting of a value presented in the column headed "g" in Table E below at one or more of entries 1 - 18 (where g ^~ the minimum humidity listed in Table B for the particular H). and h is selected from the group v the values presented in the column headed "h" adjacent the corresponding "g ^" entr\ (where h - the maximum humidity listed in Table B for the particular H ).

TABLE E: % Humidity ranges of Parameters 11(1), H(2), H(3)

P( l ), P(2), and P(3) have expected maximum pressure ranges as listed in Table B. Preferred pressures or pressure ranges within these expected maximum pressure ranges for each of these parameters are listed in Table F. Thus to choose a particularly preferred pressure range i atm - j atm for a particular P, i is selected from the group consisting of a value presented in the column headed "i" in Table F below at one or more of entries 1-27 (where i o the minimum humidity listed in Table B for the particular P), and j is selected from the group of the values presented in the column headed "j " adjacent the corresponding "i ^" eiury (where j ^■ the maximum humidity listed in Table B for the particular P).

TABLE V: Aim ranges ol Paraiiielers I'd), l ^» (2). I*(3)

The present invention contemplates amongst other things methods and processes for the processing ot cheese and ihe production ol cheese Δ\U\ cheese based snack foods and home microwaveable snack food products and cheese and cheese based stable long shelf life consumer products, and processes method and application of electromagnetic wave energy for food product processing mclutlmg for example processes known as tempering, heating, glazing, puffing, cooking, browning, leavening, drying, vaporising, pasteurising anil sterilising and using tor example microwave ( MW) and radio frequency (RF) energy and in Ira-red (1R) radiant energ\ .

The processes of present invention may be adapted to a method of production suitable for industrial commercial application lor the prodticiion of the products either on a batch process basis and most preferably on a continuous flow production basis.

The invention includes within its scope a method of production in which the various processes involved in the overall production process are carried out in predetermined and programmable sequential steps either singly or in combination of more than one process proceeding concurrently and simultaneously and being at all times under the automatic control of a feedback control system which responds continuously to the condition of the product throughout the course of the overall production process.

The processes of the second and third embodiments may be adapted whereby the commonly known and observed product changes which occur during product processing including for example the phenomena ( leavening, puffing, glazing, skin effects, drying, browning, edge burning, striping and volatilising are pre-determined and quantified and controlled for each siep or siage the overall production process such as to enable a person reasonably skilled in the art to repeat the method and process for the continuous production of the product to a high standard of physical uniformity and product quality.

The processes of the first to third embodiments may be adapted in many instances to operate at temperatures sufficiently low to eliminate or minimise the damage otherwise caused to the physical properties of the product during processing and to reduce to a low value or to a minimum the volatilisation of aromatic substances and oils contained in the product.

The processes of the first and third embodiments may in many instances be adapted to substantially reduce, or minimise or eliminate product spoiling changes which typically

occur in the product physical form and cellular structure and surface condition during processing using conventional technologies, including for example, the phenomena of product surface changes, formation of hardened surface and skins, loss of colour, loss of flavour, glazing, browning, edge burning, chewiness, non-uniform processing, excessive drying and product exploding.

The processes of the first and third embodiments may in many instances be adapted to provide relatively short product residence times and hence increases production throughput and energy efficiency.

The meaning of "spoil" throughout the specification and claims is to be taken as meaning that a material thai is spoili is no longer suitable for its intended use because it has been spoili. For example the undesirably altered appearance of processed material, tough skins on processed material, lack of nutritional value of processed material, chewy texture of processed maierial or bland taste devoid of any significant distinguishing flavour or taste of processed maierial may, depending on the intended use, constitute spoilt processed material.

Brief Description of Drawings

Fig. 1 is a block diagram depicting a preferred system of the invention;

Fig. 2 is a Process Block Diagram;

Fig. 3 Process Step I - Block Diagram; Fig. 4 Process Step 2 - Block Diagram;

Fig. 5 Process Step 3 - Block Diagram;

Fig. 6 Process Step 4 - Block Diagram;

Fig. 7 Typical Microwave Processing Chamber - Components where

1 . Tuned Microwave processing chamber - atmospheric or vacuum. 2. Microwave generators ( Magnetrons) and waveguides.

3. Dry air pressurised microwave launches with windows.

4. Controlled Temp. /humidity supply air plenum & inlets from heat pump.

5. Saturated vapour manifold & outlets to heal pump. 6. Water load microwave emission choke sections.

7. Variable speed produc t eo evoi

8 Processing chamber λ; equipment housing

9. Return conveyor assemblv .

Figs 8(a)-(e) Typical Microwave Processing Chamber - Alternative sections; Fig. 9 Microwave Power Control System - Schematic,

Fig. 10 Integrated Processing System Microwave Power Control - Schematic;

Fig. 1 1 (a) Microwave/Heat Pump System - Schematic Diagram (Pan (a));

Fig. 1 1 (b) Microwave/Heat Pump System - Schematic Diagram ( Part (b));

Best Mode and Other Modes for Performing Invention Referring to Fig I a system 100 tor removing water trom a material is depicted. System 100 includes apparatus 101 which prepares a starting material to be processed into a suitable form for processing The type ol machine/mechanism/device/appliance employed for apparatus 101 depends on the naluie of the starting material and the characteristics required of the processed product trom the starting material The starting material inputted into apparatus 100 may be solid, liquid or viscous torm, tor example. Typically apparatus 100 receives pieces or links ot material which have been pre¬ formed or sliced or diced or cut or pressed lo a pre-determined size and shape and/or weight relative lo the end product speul icaiion I e preparation ol the starting material into its preferred form for subsequent processing includes for example such preparation processes as grinding, mixing, adding ol condiments, emulsifiers. flavours, and other additives typically in standard proportions in accordance with the recipe of the particular product and blended tor unitoπmiy ot the starting material tor presentation for production processing. Apparatus 101 is primarily concerned with the controlled delivery and presentation for processing ot the prepared starting material at the appropriate temperature, in the appropnatc tor . toi example in extruded viscous form as continuous strips or drops or other shapes oi as cold links ot starting material - all to predetermined size, shape and unit w eight designed to sun the subsequent processing energy system and the characteristics ol ihe product material and end product specifications and quality control For example, apparatus 101 could include: (i) a steam kettle which heats the starting material changing it into a viscous torm and then drops predetermined amounts onto a conveyer system for subsequent processing; (n) a

dicing machine that dices the starting matenal Λ\ \ places the diced material in solid form onto a conveyer system, ( in ) a slicing machine that slices the starling material and places the sliced material in solid torm onto a com ever system: (ιv) a de-seeding or de- stoning machine optionally in combination with (ιι) or (in); (\ ) an extruder which deposits discreet predetermined amounts of viscous starting material in a particular shape or into containers on a conveyer system; ( vι) a hopper; or (vn ) an auger/pump which deposits granular/ground/slurry/viscous materials onto a conveyer system. Starting material is . ^' eύ into apparatus 101 v ia input conveyei system 102. the delivery capacity of which is governed by variable speed conveyer drive 103 which is connected to material presentation processor 107 \ ιa line 108 The temperature of the starting material passing into apparatus 101 is measured by temperature sensing device 104, which is coupled to processor 107 via line 109. and the temperature of the material leaving apparatus 101 via output conveyer system 106 is measured by temperature sensing device 105. which is coupled to processor 107 via line 1 10. Heater/cooler 1 1 1 is coupled to processor 107 via line 1 12

At least a partial barrier to moisture vapour transfer through the surface of the material is provided during processing in processing chamber 1 13. in which material inputted therein via conveyer system 106, is sul ected lo a controlled temperature and humidity environment which is maintained by heat pump 1 14 which is coupled to chamber 1 13 by lines 1 15 and 1 16 Heal pump 1 14 includes vapour exhaust 1 17 and is coupled to control processor 1 19 bv line 1 18 ^" I emperattue sensor 120, which is coupled to chamber 1 13, is coupled to processor 1 19 via line 12 1 . Pressure sensor 122, which is coupled to chamber 1 13. is coupled to processor 1 19 via line 123. Humidity sensor 124, which is coupled lo chamber 1 13, is coupled to processor 1 19 via line 125. During processing, the environment m chamber 1 13 is maintained at a temperature, typically a predetermined temperature or range of temperatures, which is/are less than that which would spoil the material, and. in which the partial vapour pressure of water of said environment is below saturation whereby the material is not spoilt by burning or substantial cooking, for example, during simultaneous irradiation of the material in the environment with infra retl radiation Λnύ microwave irradiation, which spoils the material. Infra red radiant healers 126. which are coupled to chamber 1 13. are coupled to processor 1 19 via line 127. M icrowav e generators 128. which are coupled to chamber 1 13. are coupled to processor 1 19 via line 129. Infra red radiant heaters 126

and microwav e generatoi s 128 av b used to sι nuιlianeoιιsl\ oi sequentially irradiate the material in chamber I X w ith mt i .i i cil ladiaiion and miciowave irradiation, the amount ot mtra led ladiaiion being stil l ic iem to at least partially seal the surface ot the material to provide al least a pal lia! bai nei lo moisiui e v apoui tianster through the surface ot the material w ithout spoiling the material by . lor example, burning or substantially cooking the maierial . oi toi mmg a surface barrier which spoils the material, and said amount ol mic iowav e n radiation being sutlicient to cause a slight positive vapour pressure within the matenal to prevent the material trom deflating, wherein the amount ot said mic iowav e iπadiation is not sulticieni to spoil the material by, tor example, substantial lemov ing moisiuie trom the material, burning, substantially cooking or causing surlace damage w hich spoils the material During processing in chamber i n ihe lollow ing paiainetei s ol the cnv iionment therein are simultaneously maintained (ι ) the temperatuie ol the env iionment. dnύ. (n ) the partial vapour pressure ol water ol the cnviionment below saturation, whereby the material is not spoilt during sinuiltaneoiis n i adialion ol the matenal in ihe env ironment with infra red radiation and microwave irradiation Typically the pressure is also controlled during processing in chamber 1 1 1

Material from chamber 1 1 3 is transported to piocessing chamber 130 via conveyer system 131 which is driven by variable speed drive 132 which in turn is coupled to processor 1 19 via line 133 During processing the material in chamber 130 is subiected to a controlled temperature, pressure and humiditv env ironment, which are maintained by heat pump H4 which is coupled to chambei HO by lines H5 and 136. During processing moisture is removed I rom the material m chamber 130 Heat pump 134 includes vapour exhaust 1 37 anil is coupled to control pi ocessoi 1 39 by line 138 Temperature sensor 140, which is coupled to chamber 130, is coupled to processor 139 via line 141 Pressure sen so i 142. which is coupled to chambei 130. is coupled to processor 139 via line 143 Humiditv sensoi 144 vvhich is coupled to chamber 130, is coupled to processor H9 via line 145 Mici ow av e generatoi s 146, which are coupled to chamber 130, aie coupled lo piocessoi H9 v ia line 147 During processing microwave generaioi s 146 iπadiate the matenal in chamber HO with an amount of microwave irradiation effective to increase ihe moisture at the surface ot the irradiated material whereby the vapour pressure at the surface is greater than the vapour pressure of the environment whereby moisiure is iranslerred trom the surface to the

4 ^ environment, wherein the amount ot said microw ave irradiation is not sufficient to spoil the material by. tor example, burning, ov ercooking or causing surface damage.

During processing in chambei I U) the lollow ing parameters ol the environment therein are simultaneously maintained: (i) the temperature of the environment, and, (ii) the partial vapour pressure of watei ol the env ironment below saturation, whereby the material is not spoilt during irradiation ol the material in the environment with microwave irradiation During processing in chamber 130 the amount of microwave irradiation is sufficient lo substantially maintain said vapour pressure at the surface, until a required amount of moisture has been removed from said material, without reducing the surface temperature ol the matenal more than 50% of the wet bulb depression of the environment.

Processed material from chamber 130 is transporied lo sieπlising/finishing chamber 148 via conveyer system 149 which is driven by variable speed drive 150 which in turn is coupled to processor 139 via line 151 . Temperature sensor 152, which is coupled to chamber 148, is coupled to processor 153 via line 154. Cooler 155 which is coupled to chamber 148, is coupled to processor 153 via line 156. Microwave generators 157, which are coupled to chamber 148. are coupled to processor 153 via line 158. During processing microwave generators 157 irradiate ihe material in chamber 148 with an amount of microwave irradiation el lective lo sterilise the processed material from chamber 130. The sterilised product is transported from chamber 148 to storage container 159 via conveyer system 160 which is driven by variable speed conveyer drive 161 which, in turn, is coupled lo processor 153 via line 162.

Processors 107, 1 19, 139 and 153 are coupled to integrated systems control processor 163, via lines 164, 165, 166 and 167 respectively. In use, starting material is transported al an appropriate rate into apparatus 101 via conveyer system 102 which prepares the starting material into a suitable form for processing. The appropriale rate of conveyer system 102 which is determined by the downstream processing rate in chambers 1 13. 130 and 148 is governed by variable speed conveyer drive 103 ihe speed of which is controlled by a signal from processor 107 via line 109. processor 107 being controlled by processor 163 via line 164. The temperature of the starting material passing into apparatus 101 and leaving apparatus 101 is measuied by lemperaiure sensing dev ices 104 and 105. which send signals to

processor 107 via lines 109 and 1 10 respectively , which in turn sends signals to heater/cooler 1 1 1 via line I 12 to adμist the temperature of ihe maierial in apparatus 101 whereby the material leaving apparatus 101 is at a predetermined temperature.

At least a partial barrier to moisture vapour transfer through the surface of the material is provided during processing in processing chambei 1 13. Material at a predetermined temperature from apparatus 101 i inputted into chamber 1 13 by conveyer system 106. The controlled temperature and humidity env i ronment in chamber 106 is maintained, during processing, by heat pump 1 14 which is controlled by processor 1 19, via line 1 18, (which in turn is controlled by processor 163 via line 165). which receives signals from temperature sensor 120. via l ine 12 1 . pressure sensor 122. via line 123. humidity sensor 124. via line 125. at a temperature, typically a predetermined temperature or range of temperatures, which is/are less than that which would spoil the material, and, in which the partial vapour pressure of water of said environment is below saturation whereby the material is noi spoilt during irradiation \ ^' the material in the environment with microwave irradiation. During processing infra red radiant healers 126 and microwave generators 128 are controlled by processor 1 19 via lines 127 and 129 (which in turn is controlled b processor 163 via line 165) simultaneously or sequentially irradiate the material in chamber 1 13 with infra red radiation and microwave irradiation, the amount X infra red radiation being sufficient to at least partially seal the surface of the material to provide at least a partial barrier to moisture vapour transfer through the surface f the material (i.e. surface condition the material for later processing such as puffing, for example) without poiling the material, such as, for example, by burning or cooking the material , or damaging the surface of the material , and said amount ot microwav e irradiation being sufficient lo cause a slight positive vapour pressure within the material lo prevent the material from deflating, wherein the amount of said microwave irradiation is not sufficient to spoil the material, such as, for example, by burning or substantially cooking the material, or damaging the surface of the material. During processing in chamber 1 13 the following parameters of the environmeiu therein are simultaneously maintained (i) ihe temperature of the environmeiu. and, (ιι) the partial vapour pressure ol water o. ^' the environment below saturation, whereby the material is not spoilt during processing. Typically, the pressure is also controlled during processing in chamber 1 13 typically slightly less than atmospheric to avoid vapour emissions from chamber 1 1 .

After processing in chamber I H matenal therel iom is transported at a controlled rate to processing chambei HO via conv ev ci sy stem I H which is driven by variable speed drive 132 which in turn is controlled by processoi 139 via line 1 33 (which m turn is controlled by processor 163 v ia line 166) The controlled temperature, pressure and humidity environment in chamber 130 is maintained, during processing, by heat pump

134 which in turn is controlled by processoi H9 via line 138 (which in turn is controlled by processor 163 via line 166), which receives signals from temperature sensor 140, via line 141 , pressui e sensoi 142, v ia line 143. humidity sensoi 144, via line 145. During processing moisture is remov ed from the material in chamber 130 Microwave generators 146. which aie w hich .ti e controlled by processor 139 via line

147 (which in turn is controlled by piocessoi l (X ia line 166) irradiate the material in chamber 130 with an amount ol microwav e irradiation effective to increase the moisture at the surface ot the irradiated maierial hereby the vapour pressure at the surface is greater than the vapoui pressure ol the environment whereby moisture is transferred Irom the surface to the enviionment w herein the amount of said microwave irradiation is not sufficient to spoil the material by for example, burning, overcooking or causing surface damage. During processing in chamber 130 the following parameters of the environment therein are simultaneously maintained (i ) the temperature of the environment, and, (n) the partial vapour pressure ol water of the environment below saturation whereby the material is not spoilt during irradiation of the material in the environment with microwave irradiation During processing in chamber 1.30 the amount of microwave irradiation is sufficient to substantially maintain said vapour pressure at the surface, until a required amount ot moisture has been removed from said material, without reducing the surl.t e temperatuie ol the material more than 50% of the wet bulb depression ot the environment.

Processed material Irom chamber I M) is transported to sieπlising/fmishmg chamber

148 via conveyer system 149 which is driven by v ariable speed drive 150 which in turn is controlled by processor 139 v ia line 15 1 (w hich in turn is controlled by processor 163 via line 167). The temperature in chambei 148 which is sensed by temperature sensor 152 and which sends a signal to processor 153 via line 154. is typically determined by cooler 155 which is controlled by processor 153 via line 156 and microwave generators 157. which are controlled by processor 153 via line 158 (which in turn is controlled by processoi 163 via line 167). During processing microwave

generators 157 irradiate the material in chamber 148 w ith an amount of microwave irradiation effective to sterilise the processed material I rom chamber 130. The sterilised product which may be packaged in chambei 148 is transported I rom chamber 148 to storage container 159 via conveyer system 160 which is driven by variable speed conveyer drive 161 which, in turn, is coupled to processor 153 v ia line 162 (which in turn is controlled by processor 163 v ia line 167)

As will be apparent from the abov e description the overriding control, coordination and integration of processors 107. 1 19. 139 and 153 ΛW determined by integrated systems control processor 163. via lines 164. 165. 166 and 167 respectively . The processing system typically comprises four (4) distinct steps as described above with reference to Fig. I and as is il lustrated in Fig. 2. These steps include:

Step 1. (Material Pre- rocessing)

• This step is as described abov e, and .is show n m Figs. 2 and 3, receives the starting material in natural or pre-processed form over a wide range of maierial temperatures and converts the material into a physical form suitable for processing and delivery of the material al a pre-delermined temperature to the initial processing Step 2.

• The Step I process typically utilises standard industry product preparing machinery and standard industry heating and cooling systems and control equipment for this process. The end physical form of the product and method of delivery, and applications to the conveyor systems in step 2 is peculiar lo the invention process.

• The optimum physical form and temperature and method of preparation of the start material is determined for each product as described above and having regard to whether the raw material is from bulk storage in viscous or solid form or in a hot viscous form direct from an upstream process or in fresh or processed form.

• The processing capacity and delivery rate of the product preparation and preparation apparatus is controlled by the dow nstream processing capacity of Steps 2-4.

• By way of example, the Step 1 apparatus lor the preparation and material sou reed from an upstream production process w ould n cό only to comprise a positive displacement pump and applicator system ith pipework heating and cooling means

to deliver the start malei ial thi ough an e\iuιdeι lo the piecise dimensions and temperature and pacing toi enii v to and piocessing in Step 2

• In othei examples, the apparatus ol Step I mav comprise standard industry slicing, dicing, peeling, cutting, skinning stoning, boning, filleting, type machinery fitted with specifically designed deliv ei v presentation apparatus and/or microwaveable processing containei s toi the iiansport ot the product concerned.

• By way of further examples, cheese products may be in solid toi m ol natural and processed cheese- or cheese-based products ot various shapes anil sizes and presented to Step 2 at various tempeiatures • The requirements spe i l ied in Slep 1 also suit the processing ol many other materials, tor example those listed abov e This list ol examples shows that the potential range ot products mav be in liquid oi viscous oi solid torm and in whole or reduced torm, natural or pre-piocessed and across a wide range ot raw product temperatures. • Typically, an "optimum" processing input lemperaiure and physical form of the product is first determined to establish Step 2 "process start condition". These product requirements could noι mall \ be met by using standard industrial process machinery and control systems

Step 2. (Initial Processing) • The initial processing step, which is in accordance with the first embodiment and related clauses and is described abov e, and show n in Figs 2 and 4. is a process carried out undei a controlled processing environment condition at atmospheric or sub-atmospheric pressure depending on the product

• The step incorporates infra-red radiation optionally mic rowave processes and a vacuum pump vapour extraction/condensing heat pump environmental control system to maintain the processing environment pressure, temperature and saturation condition.

• There is also provided an m I ra- red radiant healing system integrated with the heat pump drying and microwav e systems w hereby the surface condition of the product may be pre-conditioned il leqiured to increase ihe resistance ot the surface ot the product to the passage ol waier vapoui And volatile compound vapours emanating from within ihe product

• It should be appreciated that the pioduci surl.ice conditioning process which, by way ol example, may include the loi ni lion ol a sui lace skin or glazing or melting or hardening 01 othei loi m ol i eduction the surface porosity ot the product and which does not spoil the pioduct, is to create a barrier ot resistance to the passage ot vapoui s trom w ithin the pi oduci resulling in turn to an increase in the internal vapoui pressures as heat is applied to the product and especially invasive heating such as mic iowav e heating and causes the phenomenon known as "puffing" as the vapoui s tiiulei pressiue break through the product surface barrier • The processing ambieni env iionmeni lot this processing stage is typically maintained at a pre-determined adμistablc piessure selected to best suit the processing needs ol the product concerned Bv wav ol example the ambient environmeiu piessui e may be aimosphei ic but pi elerably sub-atmospheric and selected to take advantage ot the know n ledticlion in vaporisation temperatures with reduction in ambient piessures

• In processing applications in which the processing environment is required to be maintained at sub-aimosphei ic (vacuum) conditions toi example greater than lOOOPa negative, the product entry and leaving conveying apparatus incorporates a conveyor transler mec hanism w heieby the continuous product entry and exit from Step 2 is accomplished without signif icantly affecting the processing environment pressure in Step 2 processing chamber

• By way of example, tor liquid, viscous and granular or diced material, this transfer may be accomplished by the use ot interlocked rotary valves in the inlet and discharge transport systems in Siep 2 • For other materials traiispoi ted on coin ey oi belt oi on pallets or in containers this transfer may be accomplished by a tianspaieni transler mechanism via can "air lock" neutral piessure .one having intei locked an sealed access doors or slides connecting between the Step 2 transport system and the respective feed and discharge conveyors. • By way of further example where the process in Step 2 is to be carried out at atmospheric pressure oi sub-aimospheric pressures not exceeding 1000 Pa negative (to prevent vapoui emission to the surrounding atmospheric) the product

conveyor transfer di fferential pressure mechanisms may be omitted and a continuous single conv ev oi ^' sysiein used ( i t appropriate) from the delivery from

Step 1 lo the product entry at the final pac kaging stage - Slep 4.

• Step 2 control system provides for two (2) principal modes of operation. ( 1 ) microwave and 1R power control .

(2) product temperature control .

• Under power control mode the power levels of the microwave magnetrons and I. R. heaters is set to a pre-deiermined set-point in the range 10- 100% for microwave energy and 0- 100% in 10%. steps for the I. R. heaters. • The control systems maintains the actual pow er inputs relative lo the set points. Under this mode the product surface temperature is not controlled but is displayed. The environmenial control systems operates independent of the power input levels and maintains pre-determined pre-sei values of entry air temperature and saturation and pressure conditions. • Under product temperature control mode the leaving product surface temperature is set at a temperature relevant to the processing environmeiu dry bulb and wet bulb temperature and pressure and maintained by controlling the microwave power input. Under this mode the heal pump maintains the pre-set operating conditions lor the processing env ironment . The microwave power input is continuously varied to maintain the set product temperature. This control mode provides a means whereby the dry bulb and wet bulb temperatures of the recirculating ambient air/vapour mixture in the product processing chamber which incorporates integrated microwav e assisted vapour extraction/condensing, closed cycle, heat pump heating and drying system operating in a controlled, adjustable temperature and pressure environment with product temperature control is controllable relative to the surface temperature of the product being processed such that the drying process is engineered to operate as an adiabatic or isothermal process or at any pre-determined combined process between these two specific conditions, and is particularly relevant lo the processing of materials which are sensitive to higher operating temperatures and potential vaporisation or aromatic compounds. Materials in this category include for example, some cheeses, meats, fish, fruits, herbs and spices.

Step 3. (Final Processing)

• This process step, which is in accordance w ith the second embodiment and related clauses and is described abov e, and show n in Figs. 2 and 5, is a final cooking/drying/puffmg/foaming/processing stage as applicable to meet the end product specifications and incorporating continuously variable product feed back controlled electromagnetic w av e heating in a temperature and pressure controlled (atmospheric or sub-atmospheric) env ironment complete with vapour extraction/condensing system and emission control is the mam production process by microwave heating, cooking, puffing, drying as required and delivery of the finished product ready for sterilisation, pasteurisation, de-naturmg and cooling ready for packaging in Slep 4.

• Alternatively, Step 4 may for example include product de-naturmg, pasteurisation or sterilisation, cooling and packaging as a separate but integrated process. This will depend on the nature of the product being processed and whether these product processes are required, for example, as products for human consumption or industrial products.

• Step 3 may for example also include provision for infra-red radiation, browning of the finished products such as for biscuits and snack foods.

• In general respects the apparatus for Step 3 process will be similar to Step 2 apparatus and include a vacuum pump vapour extraction/condensing heat pump system and product conveyor transfer mechanism if required.

• It should be appreciated that the influence of the processing ambient environment for example with respect to operating pressure and temperature and ambient saturation condition in the final production process is affected by the microwave heating characteristics such as microwave intensity and power/time control relative to the product moisture content, surface temperature and end product specification.

• A means may be included w hereby ihe processing ambient environment for this final production stage is maintained at a pre-determined adjustable pressure to best suit the final processing requirements having regard to the entering product temperature and moisture content and final product specification with respect to such aspects for example as finished product moisture content, desired surface

texture condition and coloui . degi ec ol pu l l ing, temperature sensitivities of the product being processed and steπ l is.iiion/ti me characteristics. By way ot example the ambient envi ronment pi essui e may be atmospheric but preferably sub- atmospheric and more preferably a speci fical ly determined sub-atmospheric pressures to best suit the particular product processing characteristics and end product specification By way of furthei example typical preferred ambient environment sub-atmospheric (partial v acuum) processing pressures for the manufacture ol non-pul fmg pi oducls relei i ed to in this specification is in the range of 0.90 to 0.98 atm and tor puffing products 0.30 to 0.90 atm and for foaming products 0 10 lo 0 30 aim Otlic i pi essui e conditions are equally provided to suit specific product needs

• The control system lor Step 1 typical ly provides f or loin (4) operating modes. In its preferred form the control sub-system tor the microwave healing and processing sub-systems there is pi ovided lor example. (a) an operators control panel incorporating a series of keys and displays to indicate and control the sub-system status, operating mode, liming, power set valves vs actual , temperature set point values v s actual and parameters which define the behaviour of the PID controller.

(b) Mode key for selecting any one ot lour (4) operating modes or combination of modes throughout the complete production process and including the preferred modes ot:

( 1 ) power control

(2) temperature control

(3) power profile (4) temperature profile.

(c) A SET KEY f unction in which the preleri ed embodiment is that the set key is used to make or change the settings lor power set point value, temperature set point value, proportional , integrativ e. deriv ative and Tf parameters of the temperature controller and the settings made can be changed at any time during the process without any shut-down of the complete process or any sub-system process.

(d) In POWER CONTROL mode user can set ihe power set point value in the range from 0 to 100% . Proporiional-miegraliv e controller incorporated software maintains the actual power value relativ e set point value. The actual temperature of the heated product is displayed in this mode but is not controlled. (e) In TEMP CONTROL mode user can set the temperature set point value in the range from 0 to 200 ^C' C and proportional-iniegrative-derivaiive controller maintains the actual temperature around set point value. Power set point and actual value and temperature set point and actual values is displayed in this mode.

(f) In POWER PROFILE mode user can set up to 99 time periods (the duration of each time period can be up to 999s). for each segment user can set siarl power set point and final power set point.

(g) In TEM PERATU RE PROFI LE mode user can set up lo 99 nme periods (the duration of each time period can be up to 999s). For each segment user can set temperature set point and final temperature set point. • The operating modes provide for a wide range of set point conditions to suit the wide range of potential applications of the process.

• In lower temperature applications such as for the processing of cheeses, meats and fruits, the "temperature control" and "lemperaiure profile" the settings and operation would typically relate to the processing ambient conditions as noted for Step 2 "product temperature control " .

• A PAUSE KEY operational control on each selected magnetron or banks of magnetrons may be provided in which the operation of the PAUSE KEY will suspend the timing, function and power supply to the magnetron(s) is switched off and the filaments remain on for an adjustable pre-determined period of typically 10s on completion ol w hich the pow er supply is automatically switched off and operator alerted.

Step 4. (End Product Packaging)

This step is as described above, and as shown in Figs. 2 and 6, typically involves product microwave sterilisation and packaging and cooling stage and as noted in the specification the process of sterilisation and browning can be incorporated in Step 3. The end product would then pass through a cooling section to the product packaging machine. Industry trend is for the sterilisation of the product to be incorporated in the

1 packaging stage. M icrowave steri l isation is a proven process and appropriate packaging Λn control systems ai e com ei cial ly av ai lable. There may be provided as an integral part of the final processing stage as described in Step 1 the optional additional process of product surf ace bi ownmg w hich is accomplished for example by controlled infrared radiation ot the product as a l inal process. As an integral part of the final processing stage as described in Step 3 the optional additional process ot product sterilisation by microwave heating prior lo cool ing and/or packaging of the finished product may be included . In its pref erred form there is provided in step 3 an integrated cooking, drying, puffing, loammg and i t requi red pi oduct brow ning and sterilisation stages operating in a controlled, adμisiable temperatui e and pressure environment.

Conveyer System

There is provided m the initial and final processing stages ot the method of manufacture a product processing conveying sysiem or conveying arrangements incorporating as applicable ihe lol lowing leatures (a) transparency to microwa e radiation .

(b) Incorporating by way of integral forming of the conveying platform specific shapes, indentations or processing coniainei s and attachments constructed of microwave transparent materials in part or in whole.

(c) Means for the automatic separation of the product from ihe conveying platform or container w ithout recourse to the application of release agents.

(d) Means for the separation draining of I and reclaiming ol any oils formed in the process in such a manner as to eliminate the recycling of any oils which might give rise to burning and contamination ol ^" the subsequent products being processed . (e) Variable speed conveyor control mierlocked w ith the integrated process control system to provide a wide range ol process resistance limes.

Microwave Control & Feedback Mechanisms

General

Processing step 3 and typical ly processing steps 2 , and 4 of the invention each incorporate a microwave processing system.

The microwave power control requi rements are di Herein toi each Step The general functional requirements ol the control sy stems ai e described above for each of the

Steps.

Microwave Energy Input Microwave energy is supplied to the separate processing chambers in process Steps 2, 3 and 4 by one or more microw av e generators ( magnetrons) for each Step as determined by the product processing requirements The magnetrons may be connected to the processing chambers directly via w av eguide launc hing sections or via a system of waveguides from remote rack mounted inagneii oiis ^' I here mav be prov ided an electro- magnetic wave heat generator transmission sy tem of w av eguides and the like and generator cooling system incorporated in and i niegraied with the production machine in small capacity production machines or in preleri ed lorm as t ree standing microwave heating energy modules ith energv transmission by w ave guide connection lo the processing chambers of larger capacity pi oduciion machines. There may be an arrangement whereby the electro-magnetic wave heating energy may be transported by wave guides or the like to various locations within the production machine and at energy input levels which may be varied automatical ly to satisfy process heating and product surface lemperaiure conditions l elative to required rates ot cooking and dehydration throughout the produc tion cycle. In the preferred form the magnetrons wi ll be w ater cooled and mounted in close proximity to the processing chambei and connected thereto by purpose-made launching pieces fitted with tuning stubs, matching flanges with RF gaskets and PTFE or other microwave transparent window to separate the waveguide launching piece atmosphere from the product processing compartment atmosphere The launching piece or waveguide connection piece between the magnetron and the processing compartment is prelerably filled w ith arc detector and is slightly pressurised to above atmospheric pressure with dry air so as to increase the breakdown voltage within the waveguide undei humid environments (see Fig. 7).

The geometry of each processing compartment and the disposition of the microwave connections in its prelerred lorm i s ume l and matched lor high efficiency microwave heating performance with the mini mum ol microw ave radiation coupling between

adjacent magnetron inputs to ensure stable opei ation and smooth v ariable power control

The geometry of the microwav e processing compartments in Us preferred form has an equal sided pentagonal cross section to more ef fectively and evenly distribute the microwave energy intensity with respect lo the pioduct. Other geometrical forms of tuned microwave processing chamber designs are also suitable tor the invention process.

The processing chambers lor Steps 2 and 3 are designed to operate either at atmospheric pressure or preferably sub-atmospheric (partial vacuum) conditions. To f urther provide lor stable mic i ow av e s siem operation and to ensure the long life of magnetrons, in its prelerred lorm the magnetrons are fitted with isolators to absorb reflected energy and dissipate this energy through a dummy water load.

Effective shielding against the emission ol eleciro-magnetic waves from the microwave radiation processes carried out w iihm the machine is generally provided - such shielding complying with internationally recognised health and safety standards.

In all of the production process chambers and conv eying systems in all of their forms and configurations a level of air lightness as typically required to minimise air infiltration to the machine and to satisly the requirements for sub-atmospheric pressure operation. Microwave Power Control - General

Background information on microw ave power supply and other variables and operating modes and typical feedback arrangements tor providing constant input power stabilisation is described below

Magnetron Power Supply - Background • The efficiency of the microwav e magnetron is typically constant for a fixed load under all operating conditions To stabilise the magnetron power it is only necessary to stabilise the magnetron input powei . • The output power of the magnetron (the microw ave generator) can be influenced by: ( 1 ) mains voltage variations (the maior influencing factor).

(2) an inuease in temperatuie ol the tunic magneis This weakening the magnetic Held and loweis tlκ anode voltage

(3) changes in the RF load ich alteis the anode voltage al a given current This influence is ol lessei signilic.uice when using a mned microwave system in continuing process applications having substantiallv tixedlv, load characteristics tor example in the independent piocessing Steps 2 3 and 4 ot the invention The proposed control system in the invention calers toi these load changes

Mains Voltage Variations

• Power supply authorities do not guarantee the mains voltage will not be sub|ect to voltage variations, powei singes oi voltag s spikes which aie caused by varying loads and demands faults and switching tiansienis in the distiibuiion system

• Typically the mams stipplv is dcliveied at 220 to 240 volts AC and at a frequency ot 50 Hz or 60H/ depending on the cotintiv and disti ibulion system in place Three phase powei supply mav typical I v v.uv between 380 and 415 volts AC at 50 or 60Hz. again depending on the chaiacieπsiics ot the mam supply system

• Typically the ma s voltage mav tall bv up lo '},' even in well regulated distribution systems Unless compensated by the contiol system these mains voltage variations will cause wide tlueiuations in the output power ot the magnetrons • For example, the output powei ol a continuous wave magnetron i.ueil at 5KW at normal mains voltage can tall to 0 K\\ ith a drop in mains voltage ot \0°/<

• Typical commercially available magnetion powei contiol systems stabilise the output power against variations in mams stipplv voltage by varying the magnetron electromagnet coil current varying the filament voltage to maintain an acceptable cathode temperatuie Pio iding the internal impedance of the HV power supply is low, only small changes in the eleetiomagnet coil current are needed to produce large changes in magnetion output powei

• Figure 9 is a block diagi m showing a ivpieal magnetion Powei ontrol system using the principle ot constant input powei stabilisation which by way of example could be incorporated in the basic microwave power control in the invention

Magnetron Variable Power Control

• As already indicated the prodticiion process typically incorporates four (4) distinct processing steps as depicted in fig. 2.

• Process slep 3 and optionally process steps 2. and 4 incorporate microwave energy processing which is required to be independently controlled to respond to processing criteria relating to the particular process step.

• The optimum microwave power input lo the process will vary for different products being processed and is influenced by the interaction of the following processing parameters which will be sensed and electronically processed as signals to provide for stable system operation and continuously variable microwave power control in conjunction with the power stabilisation control noted on Fig. 9.

• The processing inputs include

( 1 ) the surface lemperaiure ol ihe product being processed al entry and exit from each process Steps 2 to 4.

(2) the dry bulb and wet bulb lemperaiure of the processing environment in Steps 2 & 3.

(3) the respective processing chamber pressure in Steps 2 &. 3.

(4) conveyor speed in each slep.

• The control system described in the invention provides for four (4) basic operating modes which are applicable to Step 3. Two (2) operating modes apply in Step 2 and Step 4.

• The four modes are:

( 1 ) agnetron power control . (2)Product lemperaiure control. (3)Microwave power profile. (4)Product surface temperature profile.

• The most appropriate operating mode or combination of modes throughout the manufacturing process will be dependent on the product characteristics and the end-product specification.

• The product characteristics and end product specification will fundamentally determine the optimum processing env ironment e.g. whether at atmospheric

pressure or slight or substantial sub-atmospheric (vacuum) pressures. The processing ambient pressure w i ll be pre-determined for each product and pre-set at start up of the particular product prodticiion run. The operating ambient temperature and processing atmosphere dry bulb temperature and atmosphere saturation conditions wi ll be maintained by the vacuum pump vapour extraction/condensing, heal pump systems, indicated in Figs. 2 and 3. This control system may use commercially available control equipment and temperature, pressure and humidity sensors and feedback controls. The environment control system could be expected to operate reliably and in a stable fashion when the operating parameters are pre-set lor ihe particular process.

• The continuously variable pow er control of the microw ave magnetron energy input to the process provides a read means w hereb the lemperaiure of the product being processed can be accurately controlled to a specific set point relationship to the dry bulb temperature of ihe processing enviionmeni atmosphere. As noted previously this control feature enables isothermal and near isothermal moisture transfer to take place between the product and the atmosphere without sensible heat exchange. This control feature of the invention enables drying of heat sensitive products to be achieved in low temperature environment with appropriate vapour pressure differences. As the microwave processing requirements in each process Step will vary considerably across the range of potential product applications the microwave power control system in the invention provides for the continuously variable control of power input of each magnetron. This enables the microwave power levels of each magnetron and bank of magnetrons serving each processing chamber to be either pre-set to provide a specific power output or alternatively a profile of power outputs in each compartment to suit the processing needs of thai compartment. These pre-set conditions may be set for continuous performance at the selected power oιιipui(s) or power profile or may be continuously varied by product lemperaiure feedback microprocessor control.

In its preferred form the control sysiem will operate on a coniinuous flow production basis but may also apply lo batch type processors with the introduction of process-time (product residence time) control applied to the microwave fixed power or power profile settings.

The manufacture of microwav e magnetrons specify particular time delays 10 be incorporated in various circuits ol the pow er control system for safety reasons during start-up and shut-down of the sysiem. These safely provisions lorm an integral part of the power control system. Magnetron Power Control System

The magnetron power control system in the preferred form of the invention is depicted in Fig. 10 and provides the following basic control features:

(a) good dynamic regulation.

(b) accurate and stable pre-setting of the RF output power in ihe range 10- 100% of each magnetron for a wide range of anode voliage and anode current conditions.

(c) power related signal for filament voltage control .

(d) magnetron output power display m w atts.

(e) incorporation of protection circuits.

(f) provision for incorporating integrated system feedback signal control of magnetron power sellings.

Power Stabilisation

As previously noted the anode voliage of the magnetron depends on the AC mains voltage variations and the internal resistance of the power supply, the latter being temperature dependent. The anode current depends on the anode voltage, the electromagnet current (for some magnetron designs) and the magnetron system load.

By way of example, the following description refers to the control supply for a typical 5KW continuous wave water cooled magnetron. Other magnetron control systems will vary in control detail but not in principle.

Microwave Power Output Measurement The anode voltage signal is typically -7.2V and the anode current signal is 950mA.

Both signals are multiplied electronically such that the output Xa is proportional to the real RF power that is Xa = k(-Va)la where the proportionality constant k is used lo limit Xa to 10V (where Va is the anode voltage and la is the anode current). A voltmeter connected to the output of the multiplier can be used to indicate the microwave power.

Setting the Power

An adjustable DC reference voltage ol + I to + 10V irom a potential divider is used to set the input power level . The minimum voliage is set by the permanent voltage divider comprising specific resistor ratings During standby the input voltage to an impedance converter is kept at OV by a closing switch When this switch is operated the input voltage rises to the present v alue (lime constant t = 0. 1 sec). An mvertor is provided with a reference voliage ol - I V to - 10\

Control Amplifier

A control amplifier with P. 1 characteristics keeps the microwave power constant at the set value even when large ma s voliage fluctuations occur at low anode currents. The input signal is the dif ference between the signal l epreseniing the desired power and that representing the instantaneous pow er The signal output ot the control amplifier is limited to ± 10V by zener anodes The use of P I ampli fier provides good dynamic regulation. If necessary this regulation can be improved by converting the amplifier to a P. l D amplifier.

Power Amplifier For Electromagnet Supply

The output of the control amplifier is the input lor an integrated power amplifier which has short circuit protection and a current hmiiei This amplifier is stable in operation even at low input voltages and provides a smooth transition as the energisation of the electromagnet reverses. The electromagnet can be turned oft by a signal trom the controller. Provision is made lo prevent microwave energy being generated when anode voltage falls below the manufacturer ^' s recommendations.

Anode Current Control

An impedance converter and comparator monitor the peak anode current The output of the comparator is used to shut dow n the power supply if necessary.

Filament Voltage Control

The control system for filament voltage control utilises a standard available control package which is matched to the πlameni operating requirements of the particular magnetron characteristics. When the anode current increases, the filament voltage is reduced to prevent overheating the cathode. During w arm-up ith no anode voltage applied, the filament

voltage is 5V at nominal mams v oltage Dui mg operation, the filament voltage is reduced to 4V and theieattei c onti ol led betw een OV and 4V depending on the anode current.

In a typical filament voltage conii ol ci i cuit . a signal proportional to the magnetron current is amplified and photocoupled to the input of a TCA280A used to control a triac which regulates the fi lament voltage according to the derating curve ot the magnetron

During warm-up, betoie the anode v oltage is appl ied , the conti ol circuit is by-passed and the triac is shunted by a switch The maximum and mini mum l i lament v oltage ai e set wiih the anode voltage oft . and a switch opened to activ ate the triac

To set the maximum filament voltage the input signal is set to zero and adμisted tor a filament voltage ot 4 OV measured at the magnetron

To set the minimum filament voltage a current ol 950mA is set and adμisted for a filament voltage ot 0.5V

Start-Up and Shut-Down Procedures

These procedures are specified by the magnetron manufacturers and by way ot example typically include the following sequences

1 . Monitoring of ihe magnetron cooling c irc uit lor satisfactory operation for about 3 sec before operating the l ilament heating

2 Start cathode heating w ith a l ixeil filament voltage of 5V and allow a pre¬ heat of about 15 sec before operating the magnetron

3. Before switching on the anode v oltage, the electromagnet current should be maximum (positive) to pi event the magnetron oscillating when the anode voltage is outside the opci aimg range ol ihe pow er stabilisation circuit (i.e. when the anode voltage is less than about 5kV )

4. Power stabilisation l ilament v oltage conti ol active The r I . output power increases to the set value and is stabilised at that value

Integrated System Control This control system (see Figs 4 dnd 5) provides lor the integrated control of the sub¬ systems in process Steps I to 4 lo opei aie in continuous sequential production mode

for the manufacture of products re I erred to in the invention specification. The integrated process control system incorporates loi example lemperaiure and pressure sensing and power and time control dev ices computerised programmable logic controllers and other control and leed-back and monitoring devices and operators key board and ancillary equipment and devices necessary to control the complete manufacturing process throughout all stages of product preparation, processing and packaging in accordance with a predetermined, adμisiable. programmable, processing time profile.

The control system incorporates the following basic features: 1 . Master control including emergency shutdow n ol the mams power supply to the production machine including the supplies to the various sub-systems electrical and control panels in Steps 1 to 4.

2. Hard wired and signal inputs from machine safety interlocks and sequence interlocks for example from magneti on cooling systems, conveyors, product feed, access doors, heat pump sy stems

3. Input signals from remote sensing devices including product surface temperature measurements, heat pumps drying air DB temperature and humidity, processing chamber pressures, conveyor speeds as applicable.

4. Input signal transmitters and converters lo feedback signal form to match the particular sub-system control requirements.

5. Programmable microprocessors for ihe pre-setting of sub-system controls and process operating modes, lor example magnetron output power and profile, product surface temperature and processing chamber atmospheric dry bulb temperatures, humidity and pressures. 6. Feedback signals I rom sub-svsiems and converters to provide display of individual magnetron pow er and compartment magnetron power profile, product surlace temperatures and processing environment dry bulb temperatures humidity and pressures relative to pre-set conditions throughout the production process. 7. Centralised fault indication, display and alarms.

1

This control system may use commercially available control equipment and ancillary devices.

Vapour Extraction/Condensing Heat Pump System

(ii'iieπ Processing Steps 2 and 3 ol the invention each incorporate a vapour evacuation heat pump sysiem to automatically control the pi ocessing environment m that Slep to pre-set adjustable conditions of dry bulb lemperaiure. chambei inlet air humidity and processing chamber pressure, ranging t rom atmospheric piessure to sub-atmospheric pressures. Each include an air/vapotn extraction system and heal recovery and transfer assembly of one or more circulating lans and one oi more heal recovery and transfer heat exchangers to circulate and control the temperature and humidity of the return air/vapour returned to the produc tion chambei s a lo the v apour condensing heat pump assembly Typically there is provided a relrigeration condensing heat pump assembly comprising one or more ref rigeration compressors, evaporators, condensers, circulating fans, vapour by-pass dampers, heal exchangers and ancillary equipment and interconnecting pipeworks and control system all lorming an integrated sub-system component of the preferred production sysiem This may comprise a closed cycle vapour extraction/ condensing refrigeration system to evacuate moisture and other cooking and drying vapours Irom the f inal piocessing stage cooking and drying compartments designed to maintain the pre-set process ambient pressure and temperature conditions and to eliminate any odours or other emissions to atmosphere. There is envisaged a heat pump sy stem in w hich the heating energy to heat the dried recirculating ambient air is reclaimed h orn the reieciion heat of the vapour condensing cycle and elevated to its operational lemperaiure wholly or mainly by the reclaim and use of waste heat generated by the microwave magnetron units incorporated in the process stages.

The equipment componentry of the v apour extraction heat pump system to process the range of product applications described in the inv ention is shown in Figs. 1 1 (a) and (b). By way ot example typical rei ngeraiion suction temperature ranges from -5° to +5 ^ϋ C and condensing temperatures 40 ιo 80 ( ^' . but lower suction temperatures and higher condensing temperatures may be used

Hot drying air having evaporated moisture from ihe product being processed is evacuated from ihe processing chamber in a partly saturated condition, typically above

50% saturation and al a leav ing icmperaiui e f l typically 40-60 ^U C for example in agricultural product processing In normal operation this air passes through a sensible heat transfer heat exchanger of the plate type or preferably of the refrigeration heat pipe type where sensible heat is transferred from T l air stream lo T8 air stream when the former is at a higher temperature than T8.

Air at a reduced lemperaiure T2 bin w nh the same moisture content of Tl leaves the primary side of ihe sensible heal iransler heal exchanger. Depending on the temperature of this air. lor example being more than 5 ( ^' abov e ihe climatic wet bulb temperature in the area or containing low lemperaiure condensable vapour compounds or paniculate matter, passes through a direct contact dehumidifying heal exchange air scrubber or bypasses this equipment and enters the heat pump dehumidifying air handling unit at lemperaiure T3 at an increased saturated condition or at T2 temperature as applicable.

The heat pump dehumidifying apparatus incorporates a condensing evaporator coil preferably equipped with air to water run-around heal exchangers (recouperators) to reduce the evaporator coil air inlet temperature T4 to the lowest practical saturated temperature condition by by-passing a controlled proportion of ihe air stream sensible heat around the evaporator.

The refrigeration heat pump compressors operaie under conventional capacity step control to maintain the discharge air lemperaiure T5 I rom the evaporator coil lo a fully saturated condition with a dry bulb lemperaiure typically being 5-8"C above the design refrigerant suction lemperaiure.

Dehumidified low temperature air T5 then passes through the downstream run-around sensible heat transfer heal exchanger and leaves this heal exchanger at an increased temperature T6. typically 10 to 30' ( ^' above T5 depending on the entering condition T2 or T3. The required humidity of Ihe recirculating air ultimately admitted to the processing chamber at temperature T12 is controlled by by-passing a proportion of air T2 or T3, as the case may be. around ihe refrigeration evaporator and run-around heat

exchangers, lo mix with air ^' 1 6. This l esulis in the ai r being increased to a temperature

T7 and having the required absolute humidity moisture content required in T12.

The dehumidified controlled moisiui e an T7 is tli avv n by a v ariable speed fan to discharge T7 air through the primary air cooled condenser after absorbing the fan heat. The refrigerant heat energy in the lorm ol hot relπgerant gas generated by the condensation process on the evaporator coil is translerred via the condenser to air T7 the temperature of which is increased to T8 Load balancing is achieved through the operation ot the secondary condense]

The heated dehumidified air T8 then passes through the secondary side of the sensible heat exchanger (primary side T2) and depending on the lemperaiure of T2 relative to T8 will increase the temperature ol T8 to T9

Air al T9 passes through a vacuum pump blowei unit This apparatus controls the volume of air delivered to the processing chamber and the bleed volume delivered to atmosphere to maintain the processing chamber at the pre-set pressure condition. The air entering the vacuum blower at T9 absorbs the blower waste heat and emerges at an increased temperature T10 typically being a 1 -2 C" increase above T9.

Air at T 10 then passes through auxiliary start-up heaters (using during start-up only) and then passes through an air to water heat exchanger in w hich the waste heat generated by the microwave magnelion cooling sysiem raises the temperature of T10 air for example to 50-60 ^u C with low relative humidity typically being between 10 to 20% by not limited to these temperature and humidity ranges.

The refrigerant suction temperatures and condensing temperatures and processing atmospheric conditions stated are by way of example only and relate to typical processes involving cheeses, meals, fruits and other agricultural products. The heat pump and environmenial control system as described and shown in Figs. 1 1 (a) and (b) can be used to satisfy widely varying process requirements

Heat Pump System Control and Feedback Mechanisms

The heat pump evacuation/condensing sub-sy siem described and indicated in Figs.

1 1(a) and (b) uses industry tandard sensing and signal transmitting devices for the measurement and . feedback of ihe process env ironment lemperaiure. humidity and atmospheric pressure. Standard industry microprocessoi control systems and

controllers and actuators are used lor the control ol v alves, by-pass dampers, variable speed fans, pumps and refrigeration compressor capacity controls.

In practice the optimum environment processing conditions for the processing of a particular product will be pre-determined by the physical , chemical and dielectric properties and the processing characteristics and en product specification of that product.

The control system enables the pre-set dry bulb temperature and humidity of the air entering the processing chamber (T I 2 ) and the pre-set operating atmospheric pressure of the chamber to be maintained at the pre-set conditions. Feedback signals are provided by lemperaiure and humidity sensoi s installed at the inlet of T 12 to the processing chamber and by pressure diflerential measurement between Tl and atmospheric pressure at exit Horn the chambei dnd for the measurement of product surface temperature in the processing chamber (see Figs. 1 1 (a) and (b)).

The processing environment heat pump system for Slep 2 is normally be set for a different set of processing conditions then for Step 3. The systems for each Step operate independently and can be re-set independently of each other.

The optimum processing environmeiu conditions and the temperature difference (if any) between the product surface lemperaiure and the dry bulb temperature of the processing environment are pre-set for each Step. This temperature difference is maintained by controlling the microwave input power in each Step when operating at coordinated pre-set conveying speeds.

In other examples where the processing environment temperature is of prime importance for product quality control or oilier processing reasons the control system allows for the pre-sel environment conditions to be re-set during production and then automatically maintained. The control of the microwav e input power responds to the changed environmental conditions to maintain the pre-set di fferential temperature (if any) between the environmeiu dry bulb lemperaiure and the product surface temperature. These settings may vary for each Step.

Examples

Description of Processing of Examples

Equipment

The equipment used toi processing I xamples 1 -7 comprised

(a) 1000 watt variable pow ei microw av e ov en l ilted w ith separately slep controlled 1500 watt ceramic inhaled radiant heatei w ith adμistable platform to place the material at a pre-deiei mined distance H orn ihe ladiant heatei

(b) 1000 wait variable power microw ave ov en f ined with a controllable return to zero product turntable and sepai.uely controlled mode stirrer to evenly distribute the microwave energy in the pi ocessing chambei

(c) digital scales for measuring w eight ol start material and end product weight

(d) temperature probes and dry and wel bulb theπnomelei s lor measuring the oven ambient temperature dnd humidity and product internal d d surface temperatures.

(e) microwaveable product containers to hold the sample material during the processing stages.

(f) dual container hot water melting pot to convert solid sample material into a viscous starting material at the temperatures noted in the Schedule of Examples.

(g) independent laboratory analyses ol start l inal product material

Methodology

The sample material was sourced from cool solid cheese blocks held in vapour sealed plastic containers at 4"C bulk tempeialuie For viscous material the start material was fu st converted lo a viscous torm at the required temperature by using the melting pot noted in ( f) above

The sample material in the measured weights and form noted was then placed in the pre-processing equipment described in (a; abov e

(1 ) This equipment was operated al atmospheric pressure, whilst irradiating the sample at low I09r microwav e pow ei setting with varying distances of the product below the infra-red radiant heatei and at varying times ot exposure. Processing time

and chamber temperature and humidity ,u.d pi oduc t surlaee temperature and produc bulk temperature wei e measured a ihe stai t . mid poi nt and on compleiion ol this initial processing step which equates to Step 2 of the inv ention process The data given fo the Examples 1 -7 relates to the steady slate processing conditions achieved for each sample.

(2) On compleiion of Process ( I ) ihe material w as immediately transferred to th final processing stage equipment (b ) This process w as carried out under atmospheric pressure conditions with ful l microw av e pow ei at 1000 watts input and measured processing environmeiu lemperaiure humuliiy The processing ti me and chamber temperature and humidity and product surtace temperature and product bulk temperature were taken at the commencement , mid point and on completion of this processing step which equates u> Slep 1 ol the inv ention The data given for the Examples 1 -7 relates to the siea v state processing conditions achieved for each sample.

The data for the respective samples I to 7 referred to in the Schedule of Examples relates to the temperature, humidity and pressure parameters noted in the invention process as T(0) H( 1 ) and P( 1 ) etc.

The corresponding daia for the Examples 1 -7 was as follows.

*WBD= Wet bulb depression

Example X

This test example was carried oui using an industrial microwave processing machine equipped with continuously variable microwave power control , processing environment temperature humidity and pressure control and set up w ith pre-processing by infra-red radiant heating and microwave radiation. The sample maierial was a molasses based raw material which exhibits similar processing character! sties lo cheese based products.

A number of tests were carried out using difierent infra-red and microwave power inputs and processing limes, xample .S used a 21) kg sample material and was typical of many tests. The finished product had less than 2.59. moisture content and was of crispy crunchy open cellular composition

As in the case of the other Examples the measurement of the product temperatures and processing environment conditions of lemperaiure. humidity and pressure were recorded throughout the process and are summarised as follows at the stabilised processing conditions for continuous llow prodticiion.

The data was as follows:

xainple 9

A number of crispy crunchy cellular cheese snack products were produced from a variety of cheese and cheese based starting materials in both viscous and solid start condition and of different weights, shapes and si/es and starling temperatures ranging from 4°C to WC. In excess of 50 sample products were produced in a process incorporating the processing steps ol the inv ention as well as including initial step for the preparation and presentation ol ^" ihe start material followed by an initial processing step including microw av e and infra-red radiant heating and a final microwave processing slep under atmospheric and sub-aimospheπc pressure conditions and in different combinations of these processes The processing equipment used compressed a combination of domestic and industrial microwave processing equipment as described operating under controlled conditions.

By way ot example a typical analv ses ol ihe cheese starling material and sample products was measured .is lollow s

The sample products across ihe range ol shapes and sizes were open cellular slightly puffed and ol crispy crunchy texliiies lightw eight and tasty The average loss in weight between the l inished product and ihe sheet material roughed from 40%- lo 56% depending mamlv on the moisture content ot ihe start material and fat content.

Depending on the degree ol puffing ( hi i is continued by ihe piocess) the volumetric increase of the sample products with respect to the volume ot the start material varied between 47% and 282 %

The physical form, weight, shape and dimensions ol Ihe starling material was recorded for each Example together with processing ambient conditions, product temperature (bulk and surtace) , mtra-red and microwave power levels and process residence times in each processing step Also final produc t w eight and dimensions The resulting data has established the typical processing relationships between the start product variables and the mic i ow av e pow ei input and process residence time for the specific product pio uciion Piocessing data relating to three examples in this group ot tests is detailed m Lxamples I lo

Kxainplc 1 (1 A series of products were produced I rom a "Tastv Matured Cheddar Cheese" start material in solid and viscous lorm and ot ditlerent weights and sizes. The products produced were unitoi mlv conloi mablv open cellulai crispy crunchy cheese snacks

which maintained a similar weight loss for the process across a range of processing temperatures from 66' to 90' ( ' and residence times ranging from 88 seconds to 240 seconds.

The end products were slightly puffed depending on the exieni of infra-red pre¬ processing. The start material and finished product analyses was as follows:

Example 1 1

A similar range of products as noted in Example 10 were produced in Example 1 1 using a "Romano" cheese as the starting material.

These samples were processed over a range of temperatures from 70° to 125°C to produce a range of highly puffed cheese "cookies" and "buns" of the open cellular crispy crunchy form. Depending on ihe induced degree of puffing "the cellular structure varied over a range from uniform open cells to rough surface texture with explosive puffed openings. The comparative analyses of these samples was a follows:

The processing data relating ιo ihese tw o examples in this series of tests are as for examples 4 and 5.

Example 12

A further series of products were produced in the same range as for Example 10 but using "Papato" cheese as the siart material .

These samples were processed ovei a l ange ol temperatures Irom 65 C lo 90°C and produced a range ol open cellulai slightly pul led c rispy cheese snack products generally similar to Examples 9 and 10 ^' I e comparative analysis ot these products was as follows:

The processing data relating to iv\ o examples in this series ol lests is as for examples 6 and 7.

Shapes of Examples 9- 12

Cheese Snack

(Cracker different shapes and sizes generally below 50mm x 50mm or 50 mm diameter.

Cheese Biscuits and Wafers

Any shape and sizes, typically up to 150mm x 100mm but say size (o suit commercial market.

Cheese "Cookie" or "Scone"

Typically less than 80mm diameter and pul led to open cellulai lo semi-spherical shape or form. Puffed 15-25mm in height

Cheese Bun

Highly puffed. Typically more than 80mm diameter and pul led to 25mm or more in height.

Example 13

This example relates to an industrial animal leed product comprising a sugar cane molasses base material and additiv es ol Hour mill bran and pollard and calcium hydroxide in the approximate proportions:

Molasses 147, .

M i l l Run 249.' .

Ei me 2 %

The typical analyses of molasses is:

Sucrose 35 %

Reducing sugar 15 %,

Inorganic products 15 %

Water 20%

Organic products 15 %

Sample products were produced from a viscous starting material at a temperature ranging from 20-40 ( ^' introduced through an extruding device in the form of cylindrical pellets, continuous strips and large biscuit lorm. The processing of the material was carried out under control led atmosphere temperature and humidity at sub-atmospheric pressure in the range from 250- 1000 Pa vacuum. The surface temperature of the maierial was com ml led between 80- 1 15°C under various microwave power inputs and conveyor speeds. The sample products were puffed to varying degrees depending on the physical form of ihe entry material and in particular the surface area versus the volume of the entry material . Al l start material was reduced to a moisture content of less than 2.5 % of final product w eight and had an open cellular structure and crispy nature. The average 2 1 % reduction in weight during processing was due to the reduction in water content and some losses of low temperature gum and wax volatiles. The processing data relating lo one example in this group of tests is as per example 8.

Animal feed product in pellet form - typically 20-30mm diameter and up to 50mm in length. A biscuit form is typically in square or rectangular form in any dimensions to suit marketing. The product Can be further processed by hammer milling into a sugar like "pourable" material as a fv d addit ive. Example 14

Further tests have demonstrated that this process described in the invention is for example suitable for ihe drying of products such as meats, fish, poultry, fresh fruits, such as berries, vinecrops.

These products are al l sensitiv e lo di ing conditions and in particular drying conditions which cause deterioration or hardening or discolouration ol the surface ot the product.

The controlled processing env ii onmeni conditions and abi lity lo control the surface temperature of the product and the microw ave input energy enable the above products to be dehydrated whi lst retaining ihe qual ity ol the I resh material in terms of colour, texture, skin properties. Ilavoui and low volatil isation temperature aromatic compounds