This invention relates generally to pasteurisation and to the pasteurisation of foodstuffs. More specifically, although not exclusively, this invention relates to an improved method for the pasteurisation of foodstuffs and apparatus for effecting such pasteurisation.

Pasteurisation in the process made famous by Louis Pasteur during the 19 ^th century whereby relatively gentle heating of a substance was capable of killing most of the inherent bacteria to prevent spoiling of the foodstuff. In particular Pasteur showed that beer, wine and milk were all susceptible to pasteurisation which prevented or inhibited spoiling and thereby increase longevity.

Today it is known within the food industry to pasteurise many foodstuffs to prolong shelf life. Moreover, there are plural techniques available to manufacturers to lengthen shelf life. For example, milk can have a shelf life of two to three weeks if pasteurised using high temperature short time (HTST) techniques and for up to nine months when subjected to ultra-heat treatment (UHT).

In particular, guidance in the UK (as set out in Pasteurisation : Ά Food Industry Practical Guide - Second edition Guideline No. 51 ' (2006), Published by Campden Bri) states that there are two pasteurisation regimes, depending upon the desired shelf life of the product. In the first regime (for a shelf life of <10 days) the foodstuff is held at a temperature of 70°C for 2 minutes (or equivalent thereof) and in the second regime (shelf life >10 days) the foodstuff is held at a temperature of 90°C for a period of 10 minutes (or equivalent thereof).

The newest technology to effect pasteurisation in milk is microwave volumetric heating (MVH), whereby microwaves are used to heat milk passing in a continuous flow mode. It is said that because MVH delivers energy evenly to the whole body of flowing milk, it allows for gentler and shorter heating, thereby preserving the taste of the milk because more of the heat-sensitive substances therein are preserved.

An example of an MVH apparatus is disclosed in WO2011/048349. In that patent application a substance flowing through a microwave-transparent pipe is subjected to microwave energy admitted into a microwave resonator which is coaxially located with respect to the pipe.

Whilst the above-described apparatus may be capable of MVH of a bulk flowing fluid it is not capable of effecting MVH of a discrete package.

It is an object of the current invention to provide a method, process and/or apparatus capable of pasteurising a packaged foodstuff using microwave energy.

A first aspect of the invention provides an apparatus comprising conveying means on which one or more sealed packages of fluid foodstuff are conveyable, a microwave zone through which the conveying means extends to convey said one or more packages, the microwave zone being a zone in which microwave energy is directed or directable to packages being conveyed therethrough by said conveying means and turbulence inducing means capable of inducing turbulence within said packages before, in and/or after the microwave zone.

A further aspect of the invention provides an apparatus for processing foodstuffs, the apparatus comprising a belt conveyor or belt conveying means on which one or more sealed and flexible packages of fluid foodstuff are conveyable, a microwave zone through which the belt conveyor or said belt conveying means extends to convey said one or more sealed and flexible packages, and in which said packages being conveyed through the zone by and upon the belt conveyor or said belt conveying means are exposed to microwaves, and turbulence inducing means, device or apparatus capable of inducing turbulence, preferably periodically and repeatedly inducing turbulence, within said packages supported on the belt conveyor or said belt conveying means before, whilst in or being conveyed through and/or after the microwave zone.

It has been surprisingly found that in contrast to the MVH process described above, when a sealed package of fluid foodstuff is subjected to an MVH process the energy density generated within the package is not necessarily uniform, leading to the potential for hot or cold spots to be generated within the package. Non homogeneous energy density and/or hot or cold spots can lead to flavour impairment of the foodstuff within the package, which may result in the entire package being wasted. Moreover, inhomogeneous energy density may lead to sub-optimal pasteurisation. By causing a flow or turbulence within the package, the effect of a non-homogeneous energy distribution can be mitigated. The turbulence inducing means may enhance the natural convection within the package caused by the heating of the foodstuff through exposure to the microwave energy.

The belt conveying means may be capable of conveying sealed and flexible packages of a volume to have a mass of in excess of 1 kg and preferably in excess of 2kg, for example in excess of 3kg. In a preferred embodiment the packages have a mass of from 1 kg to 20kg, for example from 2kg to 10kg, and in some embodiments from 3kg to 8kg. In a convenient embodiment the filled packages have a mass of 5kg ± 50g. Clearly, such packages are large and supporting such packages on a belt conveyor or belt conveying means is beneficial. Also, because of the size and weight of such flexible packages it is difficult in practice to invert such packages without causing damage thereto and/or whilst maintaining throughput or without locating the packages in a further container, which is time consuming, requires a further process step and may be expensive.

The package may be formed from a polymer, preferably a polymer with low oxygen and vapour permeability, and in embodiments may comprise a bilaminate film to provide the package with the necessary and/or required physical characteristics to retain and store a mass of over 1 kg of foodstuff, as set out above.

The belt conveying means may comprise an endless belt conveyor. The endless belt conveyor may be arranged to have a concave upper (package-supporting) surface, thereby to form a trough, to reduce the likelihood of spills from the conveying means, in the event of the package or one of the packages being damaged and/or being incompletely sealed.

The belt conveying means may comprise plural conveyors to facilitate cleaning of the conveying means in sections.

The microwave zone may be comprised by a microwave tunnel comprising plural magnetrons. Each magnetron or a group of magnetrons may be controllable so as to vary the amount of emitted microwave energy.

An infrared camera may be provided to determine a temperature or heat profile of or within the package. The turbulence inducing means may comprise a means to physically induce turbulence within the package for example the conveying means may travel over or across an undulating path, thereby to cause turbulence with a package conveyed by said conveying means. Additionally or alternatively the turbulence inducing means may comprise abutment means arranged to impart a force to, for example contact, a package as it is conveyed. The abutment means may periodically contact the package. The abutment means may comprise one or more reciprocating or reciprocable members arranged to intermittently or periodically contact the package as it is conveyed. Alternatively a blast of air or other fluid may be directed at the package. Because the foodstuff is preferably fluidic, and the package material is preferably thin and flexible, an impact to the bag will propagate as a Shock wave through the contents of the bag. Clearly, the more viscous the contents of the package the lower the propagation rate of the shock wave and so the size of the impact may be determined as a function of the viscosity of the contents.

The turbulence inducing means, e.g. said abutment means, may be homogeneously or non homogeneously distributed along the microwave zone.

In one embodiment said turbulence inducing means may be located at or towards an upstream end of the microwave zone.

As exposure to microwave energy heats the contents of the package, some foodstuffs will start to thicken. This may be due to thickening agents, for example starch or other components, within the foodstuff. Where the fluid foodstuff becomes thicker as a result of exposure to microwave energy we prefer to locate said turbulence inducing means at or preferentially towards an upstream end of the microwave zone.

Of course, said turbulence inducing means may be located along the entire microwave zone and some or all may be actuated, depending on one or more of the package, the sauce or conveying parameters.

The packages may be exposed to a non-homogeneous distribution of microwave energy as it traverses the microwave zone. In an embodiment the microwave energy at or towards the upstream portion of the microwave zone is greater than the microwave energy at or towards the downstream portion of the microwave zone. The microwave energy may decrease step-wise along the length of the microwave tunnel in a irregular or regular pattern. The microwave energy may decrease and increase along the length of the microwave tunnel. The microwave energy may be controllable along the length of the microwave zone. The amount of control may be dependent upon one or more of the package, the sauce or conveying parameters.

The apparatus may also comprise a package filling apparatus or package filling means. The package filling apparatus or said package filling means may comprise a hopper for holding foodstuff to be filled into flexible packages. Further conveying means may be provided between the package filling apparatus or said package filling means and the belt conveyor or said belt conveying means. Said package filling apparatus of package filling means may comprise a steam jacketed kettle.

The apparatus may comprises means to weigh the package before and/or after the microwave zone. The apparatus may comprise a package reject system. The package reject system may comprise means to determine a physical characteristic of the package (e.g. the weight and/or dimensions of the package) and to assess the physical characteristic against a pre-determined, estimated or calculated characteristic to determine if the package should be rejected.

A further aspect of the invention provides a method of pasteurising a fluid foodstuff contained in a sealed package, the method comprising providing a fluid foodstuff in a sealed package and conveying the package through a microwave zone and exposing the package to microwaves and inducing turbulence within the package to mix the contents thereof.

A yet further aspect of the invention provides a method of pasteurising packages of sauces, wherein the packages have a mass of over 2kg, the method comprising exposing the packages to microwaves to pasteurise the sauce and thereby to improve the shelf life of the sauce.

Another aspect of the invention provides a sealed flexible package (e.g. a thin polymeric bag or pouch) of sauce having a total mass of over 2kg, preferably over 2.5, 3, 3.5, 4, 4.5 kg, and a shelf life of over fifteen days. A yet further aspect of the invention provides a sealed package of fluid foodstuff formed using the apparatus of the invention or the or each method of the invention.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms "may", "and/or", "e.g.", "for example" and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

The invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view of apparatus according to the invention;

Figure 2 is a view of a bag according to an embodiment of the invention;

Figure 3 is a side elevation of a portion of apparatus according to the invention;

Figure 4 is a schematic plan view of part of the apparatus of Figure 3; and

Figure 5 is a schematic plan of a further embodiment of the portion of the apparatus of the invention.

Referring now to Figure 1 , there is shown a schematic plan of apparatus 1 according to the invention comprising a conveyer 2 and a microwave zone 3, the conveyor 2 extending through the microwave zone 3 to convey goods therethrough.

Upstream of the conveyer 2 is a package fill apparatus 4 and a supply conveyor 5 which conveys packages from the package fill apparatus 4 to the conveyor 2. As shown, the supply conveyor 5 extends orthogonally to the conveyor 2. This is convenient for space and installation reasons but is not essential. The length and speed of the supply conveyor 5 is determined according to the rate at which the package fill apparatus 4 can fill packages and/or the speed with which the conveyor 2 can accept packages.

The package fill apparatus 4 is typically a vertical form fill (VFF) apparatus, although other apparatus may be deployed.

It is preferred that a foodstuff is prepared using a traditional steam jacketed kettle system. Steam jacketed kettles are available in sizes of 300f up to 1500f from D. C. Norris & Co of Great Gransden, Bedfordshire, United Kingdom. The foodstuff can be prepared according to usual practice in anyway howsoever.

In this embodiment, the foodstuff is located in, for example pumped to, a hopper for filling into a flexible bag. We prefer to use a 5kg vertical form fill bag. The bag may be provided with a valve, for example a one-way valve to allow the bag to vent under certain circumstances. The bag may be formed from a polymer, preferably a polymer with low oxygen and vapour permeability, and may comprise a bilaminate film to provide the bag with the necessary and/or required physical characteristics to retain and store foodstuff.

The flexible bag is typically filled with the foodstuff at a temperature above ambient, for example at 35°C to 45°C, say at 40°C.

The bag is either incompletely filled to provide a potential headspace within the bag or alternatively the bag may be provided with a one-way valve. In both (and all) instances, the bag is capable of accommodating any steam or other material that could be generated as a function of heating the foodstuff within the bag.

An example of a bag 10 according to the invention is shown in Figure 2. In this case the bag 10 contains 5kg of sauce and is provided with a valve V, for example such as that disclosed in WO2004/106190.

The bag 10, once filled and sealed, is conveyed along the supply conveyor 5 and thence to the conveyor 2. The transfer between the supply conveyor 5 and the conveyor 2 may be effected by a separate transfer conveyor (not shown) to change the flow direction of conveyed packages. Other ways of transferring packages are known to the skilled person. The bags 10 are conveyed on the conveyor 2 through the microwave zone 3.

The microwave zone 3 comprises a microwave tunnel 30 having plural magnetrons to generate microwave energy to which the contents of the bags 10 are exposed.

It is preferred that the microwave tunnel 30 is provided in modular form of plural microwave subunits 30a, 30b, 30c and so on to allow for different capacity requirements. Each of the microwave subunits comprises plural magnetrons to irradiate a conveyed package 10 from different directions. In a preferred embodiment the microwave tunnel 30 comprises 36 1 kw magnetrons, distributed equally between twelve rows of three magnetrons in six microwave subunits (30a to 30f). In which case each microwave subunit (30a to 30f) will comprise 2 rows of three magnetrons.

It is preferable that each of the microwave subunits (30a to 30f) may be individually controllable such that the amount of microwave energy generated need not be the same from subunit to subunit.

For example, the profile of microwave energy generation may be as follows:

Other profiles may be deployed.

The above-described microwave profile ensures that the microwave energy to which the foodstuff is exposed is inhomogeneously distributed, with distribution being preferably towards or at the upstream portion of the microwave zone 3.

In larger units there may well be three such microwave tunnels 30, located in series. Parallel lines (each including one or more microwave tunnels 30) can be provided to increase throughput.

As the bags 10 are conveyed through the microwave zone 3 they are exposed to microwaves and the contents are heated to and beyond a pasteurisation value. As the contents of the bag 10 are heated volatile components (typically steam or water vapour) will be released from the foodstuff. If a valve V is provided the volatile components can escape to the atmosphere to ensure that the bags 10 do not burst. Alternatively, if the bags 10 are not filled to capacity, there will be a headspace within the bag capable of accommodating any released volatile component generated during exposure to microwaves and as a result of heating. In either case, because pasteurisation takes place in a sealed environment the loss of volatiles from the foodstuff is lower than is conventionally experienced in pasteurisation. This both reduces costs, due to the lower loss process, and helps to improve flavour.

Turning now to Figure 3, there is shown a view of the conveyor 2 extending through the microwave zone 3.

The conveyor 2 includes an endless belt 20 which runs between upstream and downstream rollers (not shown) and a drive means (not shown) to drive the endless belt 20. Also provided are plural raised members 21 over which the endless belt 20 runs.

As the endless belt 20 is driven in the direction of arrow A by the drive means over the raised members 21 the belt 20 will locally deflect upwardly, in the direction of arrow B, thereby causing an undulatory motion. The raised members 21 are located in a first array 21a and a second array 21 b (as indicated in Figure 4), the two arrays 21a, 21 b respectively engaging opposed edges of the endless belt 20 but not being transversely aligned.

In use, as packages 10 are conveyed by the conveyor 2 upon the endless belt 20 the opposed edge portions of the bag 10 will alternately rise as the bag 10 travels over the alternate raised members 21.

As the edge portions of the bag 10 is raised and lowered a motion within the contents of the bag 10 will be imparted which is orthogonal to the principal flow direction A. As the bag 10 is conveyed over successive raised members a to-and-fro motion will be imparted within the contents (indicated by arrow C). This will mix the contents and reduce the likelihood of hot or cold spots being developed.

The raised members 21 may be more numerous at or towards the upstream end of the conveyor 2. As an alternative, and as shown in Figure 5, (or indeed even additionally to the undulatory surface), it is possible to provide abutment members (21 a', 21 b') moving (e.g. reciprocating) in the direction of arrow D to jab or prod the bags 10 to induce mixing of the contents of the bags 10. The abutment members 21 a', 21 b' may be pneumatically, hydraulically or mechanically driven members, for example arms, arranged to move back and forth to engage the bags 10 as the bags 10 pass the abutment members 21 a', 21 b', thereby to induce or cause mixing of the contents as the bags 10 are conveyed on the conveyor belt 20' of the conveyor 2. In place of physical engagement, the abutment members 21 a', 21 b' may be arranged to force a stream of fluid (for example air) against the surface of the bag 10, thereby to mix the contents thereof. The abutment members 21 a', 21 b' may be preferentially distributed towards the upstream end of the conveyor 2'.

As the bags 10 emerge from the microwave zone 3 they are conveyed to a downstream conveyor and thence to a chiller C to reduce the temperature of the foodstuff below ambient and are subsequently conveyed to storage S under chilled conditions, until the contents are required for use. Conventionally the period of storage is termed work-in- progress (WIP). The shelf life of the contents of the foodstuff determines the maximum time period of the WIP. Clearly, the longer the shelf life, the better for the producer and consumer.

To provide the initial cooling, we prefer to use a spiral chiller C to reduce the temperature. This can be located close to the downstream end of the microwave tunnel 30 and efficiently utilises space.

In an embodiment of the invention, we used a microwave zone 3 having a microwave tunnel 30 which was 15 m long and had a power output of 108kW. Using such apparatus we are able to process 750kg of sauce per hour (equivalent to 2½ 5kg bags per minute). Of course, process time is dependent on the number of microwave units, or magnetrons, the microwave cross section of the material being irradiated and so on, and the actual process time may be higher or lower than set out above.

Using the apparatus of the invention we have processed plural sauces and tested them in a blind experiment to determine the effect the invention had on flavour. The results are as follows: Flavour Results

Sauce Trial 1 Trial 2 Trial 3 Conclusion Singapore M S E E

Penang M S M M

Hoisin M E E M

Thai Green Curry M S M M

Cajun M M E M

Where: M flavour of sauce processed by invention preferred

S flavour of sauce processed conventionally preferred

E no noticeable distinction

As will be appreciated, the flavour of sauces processed by the invention was, in the main, preferred and, at worst was at least equivalent to sauces pasteurised by conventional techniques. We believe, although we neither wish nor intend to be bound by any particular theory, that this is due to a reduced loss of volatiles when pasteurising using the apparatus of the invention thereby ensuring that the intended flavour is retained and/or is due to the gentler and/or faster pasteurisation regime thereby reducing flavour impairment.

Indeed, because of the reduction in the amount of volatiles as compared with conventional pasteurisation, it was possible to adjust the recipe of each sauce to reduce the amount of volatiles in the starting mixture. This is beneficial because there is less waste but it is also beneficial because the flavour of the sauce before it is used to fill the bag is much closer to the flavour of the sauce post pasteurisation, which facilitates better quality control.

In order to test the efficacy of the method for effecting pasteurisation, we conducted a series of trials using the apparatus of the invention.

Because black bean sauce has a relatively high water content and contains large particulates (i.e. fragments of black beans) it is believed that this sauce may be one of the most difficult to pasteurise using the apparatus of the invention. Accordingly, we tested this sauce as the paradigm case. To do so samples of black bean sauce were inoculated with Clostridium butyricum or Bacillus polymyxa as microbiological non-pathogenic surrogates and the inoculated sample located in a plastic capillary.

The plastic capillaries were located in bags of black bean sauce, sealed and then subjected to microwave pasteurisation, in accordance with the above description.

After processing the capillaries were recovered, the exterior washed with hydrogen peroxide and rinsed with sterile distilled water. The capillaries were aseptically cut open and then transferred to 10mf quantities of maximum recovery diluents (MRD) and shaken to recover any surviving bacteria. The resulting solutions were homogenised and serially diluted into 9mf aliquots of MRD. 1 mf aliquots from each dilution were transferred to 90mm Petri dishes and grown in Tryptone Soya Agar (TSA) or Eugon Agar + 0.1 starch (ES) for Bacillus polymyxa and Clostridium butyricum respectively.

All sample plates were then incubated appropriately and, once incubated, analysed to determine the colony forming units per mi (CFU/mi).

Control Samples

Samples were placed in plastic capillaries and then analysed as per the above but without exposing the samples to the microwaves.

Control analysis

For each organism a decimal reduction time analysis was carried out at 90°C, so that the equivalent process time at 90°C which the samples received could be calculated.

To do so, plastic capillaries were submerged in oil in a calibrated oil bath set to 90°C and removed at pre-determined time points and transferred to an ice bath to arrest the heat treatment.

The samples were analysed to calculate a D value using linear regression analysis. Results.

D ₉₀ Av. Recovery Av. Reduction Av. Equivalent

Log CFU Log Minutes at

90°C

Trial 1 Clostridium butyricum 3.60 0.00 3.77 13.57

Control 3.77

Bacillus polymyxa 5.34 0.0 5.91 31 .56

Control 5.91

Trial 2 Clostridium butyricum 3.60 0.0 3.77 13.57

Control 3.77

Bacillus polymyxa 5.34 0.0 5.91 31 .56 Control 5.91

Trial 3 Clostridium butyricum 3.60 0.0 3.77 13.57

Control 3.77

Bacillus polymyxa 5.34 0.0 5.91 31 .56 Control 5.91

D ₉₀ is determined by the procedure as set out in 'Control Analysis'

Control Av Recovery Log CFU is determined for the Control as per the 'Control Sample' above

Each result was an from an average of 50 samples

Minimum process times at 90°C of 13.57 minutes for trials 1 , 2 and 3 respectively.

As can be seen the average equivalent heat treatment at 90°C was far in excess of ten minutes for Clostridium butyricum and far in excess of ten minutes for Bacillus polymyxa. The minimum calculated log reduction for psychotropic Clostridium botulinum was 8.13. This clearly demonstrates the efficacy of the methodology.

It is desirable to have a way of monitoring the temperature in the bags as they are processed, potentially to prevent overheating which could cause unwanted damage to the bag. We prefer to use an infrared monitoring system to determine the temperature of the package 10. If the package 10 is not above a minimum temperature as it emerges from the microwave zone 3, it may be rejected. To do so one or more infrared cameras is mounted either within or after the microwave tunnel 30, we either have one or more, for example three cameras mounted 33%, 66% and 85% along the microwave tunnel 30, in the direction of travel or at the exit to the tunnel 30. If the cameras, or one of them, detects that the temperature of the package 10 is below a critical point then the package 10 may be rejected. The package 10 may be weighed to determine the weight:temperature ratio to ensure that the smaller temperature gain is not due to a greater volume of foodstuff within the package 10.

It is also preferred to monitor the weight of the package before and/or after the microwave zone. The weight of the package prior to the zone may be used to control the microwave energy which is emitted at the package. The weight of the package after the microwave zone may be used to reject a package which has likely leaked. Alternatively a height detection system, for example a laser or IR beam may be deployed to ensure that the package is a required or known height, packages below the known or required height being rejected for having leaked (or by likely to have leaked). In the circumstances, rejection may actually involve directing the package to an inspection station where a visual, manual or other check is performed to determine if the package is damaged or has leaked. A detected package leakage event may automatically trigger an alarm and/or institute a cleaning regime.

We also prefer to employ belt cleaning apparatus to remove debris from the belt of the conveyor 2. As well as being good practice, removal of debris also helps to improve the effectiveness of the microwave zone because detritus and other bodies which are not removed from the conveyor 2 may not be microwave transparent and so may reduce the available microwave density and may cause other issues upon heating. To do so, we use a brush to contact the endless belt of the conveyor 2 as it makes the return journey and we have a dry steam cleaner which periodically exposes the belt to dry steam, thereby to sterilise the surface, typically this will operate for less than 10 minutes per hour of belt operation.

In further embodiments, the packages may be located on trays, which may be flexible, so as to ensure that drips or leaks do not contact the conveyor.

The results provided herein clearly show that sauces pasteurised using the process according to the invention have better (or at least equivalent) flavours and have effective pasteurisation profiles.

We calculate that the WIP date for 5kg bags of sauce processed using the methodology of the invention is 12 days with a shelf life of up to or over 19 days. Such a shelf-life represents a significant improvement over current pasteurisation techniques and, coupled with the improved flavour and inherently lower loss process, leads to customer benefits and significant cost savings.

Moreover, because the process is continuous and in-line, and because once filled the package 10 never needs to be opened until use, the risk of downstream contamination is vastly reduced. Moreover, the immediate downstream chilling of the contents of the package post pasteurisation also mitigates the risk of subsequent biological contamination and minimises the extent of personnel handling until the package 10 has been cooled, thereby potentially improving safety.