PROCESS AND DEVICE FOR PRODUCING ICE OF GEL CONSISTENCY

The present invention relates to a process and a device capable of producing bulk ice of gel consistency containing small gas bubbles by utilizing the principle of freezing point depression of water-based liquid phase materials (basically water), for example for appli- cations falling in the fields of food processing, hotel and catering trade, therapy, industry and other similar fields requiring rapid temperature reduction.

In the field of food processing, numerous processes are known whereby icy or ice- containing products are produced through freezing point depression induced by oversatu- ration in water-based liquids, e.g. in syrups of various flavours, alcohol free or alcoholic beverages, beers, etc. by means of non-oxidizing gaseous substances. Such processes, as well as the embodiments of devices for accomplishing such processes are discussed e.g. in US Pat. Nos. 3,608,779 and 3,826,829, as well as e.g. in International Publication Pamphlet Nos. WO99/60091A1 and WO01/36582A1. A part of the documents cited here shows solutions for partially freezing ready drinks, e.g. bottled or canned beverages/beers after opening, and thus they are suitable for cooling the products during consumption. Another part of the descriptions teaches solutions wherein freezing of the previously prepared liquid products (i.e. those sweetened/aromatized, coloured according to recipe) commences just after their being dispensed into appropriate vessels (glasses, jugs, etc.) and optionally is accelerated by an external influence (e.g. by ultrasonic treatment, agitation, specifically constructed vessel surface) that stimulates the formation of nuclei, as a result of which a product containing small grained or slushy ice or ice in blocks forms. The devices for performing such processes are provided with a relatively complicated multiple cooling, which requires a series of additional units and a significant amount of energy for the production of the icy products. In addition, as the devices concerned are suitable for freezing liquids prepared previously in accordance with recipes, they are not capable of satisfying demands related to small amounts, e.g. on a household scale or demands on a very wide range as far as the taste is concerned.

Consequently, the aim of the present invention is to achieve a process for producing water-based icy products which is more economic and more efficient as compared to the processes applied nowadays, that is, which would require much less energy consumption.

A further aim of the present invention is to develop a device for producing icy products in large amounts and in a continuous manner by applying much less additional units than the presently used devices.

A yet further aim of the present invention is to achieve a device for producing icy products that is capable of producing the icy products with the exploitation of no external influence.

Another aim of the present invention is to design a device for producing icy products that is capable of satisfying demands on a wide range as far as e.g. taste or appearance of the products are concerned, even on a household scale.

Here, and from now on, the expression ,,water-based liquid" refers to at least one of wa- ter, water enriched with carbon dioxide or carbonic acid (mineral water, soda water), water - optionally enriched with carbon dioxide or carbonic acid - containing alcohol or alcohol derivatives in an amount of at most 15 weight%, preferably at most 12 weight%, more preferably at most 6 weight%, and water containing fats of vegetable and/or animal origin, mineral substances, as well as proteins in emulsion and/or dispersion (that is, milk). However, the expression ,,water-based liquid' ^'1 does not include aqueous mixtures containing for example sweeteners, flavouring substances, colouring agents, odorants and/or similar food additives.

Without being involved with a more detailed theoretical discussion, the solutions ac- cording to the present invention are based on the physical process discussed below.

To produce ice of gel consistency certain physical parameters (first of all pressure, temperature, amount of absorbed gas) are necessary. An amount of gas harmless to human health, preferably a non-oxidant gas, preferentially carbon dioxide and/or nitrogen, is ab- sorbed in the water-based liquid, and then the pressure of the liquid is increased from a given first value to a second one, while its temperature is decreased from a given first value to a second one. After that, the pressure of the thus obtained mixture of increased pressure is changed from the second pressure value to a third pressure value lower than the second one. Simultaneously, the second temperature of the liquid decreases to a third

one (to its freezing point). The water-based liquid containing the dissolved gas and cooled at a pressure higher than the atmospheric pressure freezes rapidly when getting to atmospheric pressure. For changing and setting the pressure of the water-based liquid the added gas itself is utilized, from which increasing amounts are absorbed as the pressure increases, until the liquid is saturated with the gas dissolved in it at the given temperature. When the water-based liquid is put under atmospheric pressure it becomes instable, as it became significantly supercooled at the higher (saturation) pressure, formation of ice crystals, i.e. nucleation starts. Parallel to this, a significant amount of the absorbed gas segregates in the form of tiny bubbles functioning as nucleation centres for the formation of the ice crystals within the volume of the liquid. The concentration of dissolved gas in the mixture is thus reduced. This, in turn, increases the freezing point, thus crystallization commences. Ice is mainly formed on the surfaces of the gas bubbles, which thus enclose the gas and the process leads to the formation of ice of a gel consistency (further on ,,ice jelly") of a loose structure. In course of ice jelly formation, latent heat of fusion is liber- ated which heats the liquid. The cooling needed due to this process and the pressure belonging to it are chosen so that the system remain steadily below its melting point (T _me it)- The supercooling temperature T at issue can be determined by the equation of

T ¹ - - T ' melt ^{lce C water where L _lce is the latent heat of fusion of ice and c _water is the heat capacity of water.}

If the extent of supercooling differs from the above described, when the third, preferably atmospheric pressure is reached (e.g. at tapping or on draught), as a consequence of the tapping rate determined by the difference between the third and the second pressures in combination with the tapping cross section, not all of the material racked transforms into ice of gel consistency, but only a part of it. Knowing the composition of the liquid (i.e. essentially the absorbed gas content thereof), on the basis of the above effects a person skilled in the art can easily determine the optimal temperature-pressure ranges needed for the formation of ice jelly, and the appropriate tapping rates too, by considering also the tapping cross section. In knowledge of these values, by means of a suitable device the ice of gel consistency could be produced in both household and industrial amounts.

For the case when water and carbon dioxide are used as the water-based liquid and the gas absorbed in it, respectively, the pressure-temperature diagram (i.e. the phase diagram) of the liquid obtained, and the physicochemical properties of the liquid are discussed in detail e.g. by L.W. Diamond and N.N. Akinfiev in a paper published in Fluid Phase Equlibria, 208, pages 265-290 (2003).

In light of the above, in one aspect of the invention the above objects are achieved by elaborating a process comprising the steps of

- feeding a gas, preferably a non-oxidant gas, and a water-based liquid into a pressure- tight reservoir closed in an airtight manner and provided with a gas inlet tube, a liquid inlet tube and an outlet stub at a first temperature in the closed position of the outlet stub through the gas inlet tube and the liquid inlet tube, respectively, thereby saturating the water-based liquid with the gas at a first pressure in the reservoir;

- subjecting the water-based liquid to a second pressure higher than the first pressure along with maintaining the feeding of gas, and simultaneously decreasing the temperature of the water-based liquid to a second temperature lower than the freezing point belonging to the saturation pressure;

- subjecting at least a portion of the supercooled liquid to a third pressure lower than the second pressure in the cross section of the outlet stub, and extracting said portion of the liquid from the reservoir through tapping by opening the outlet stub; whereby

- creating nucleation centres through the liberation of at least a part of the dissolved gas content of said liquid portion in the form of bubbles, and inducing a segregation of at least a portion of the water content of said liquid on these nucleation centres in the form of ice an ice product of gel consistency is produced, wherein consistency of the product is controlled by the tapping rate determined by the cross section of the outlet stub in combination with the difference between the third and second pressures.

Preferred embodiments of the process according to the invention are described in Claims 2 to 5.

In another aspect of the invention the above objects are achieved by developing a device for carrying out the process according to the invention comprising a pressure-tight reservoir enclosing an inner volume and a cooling means for cooling the inner volume,

wherein the inner volume of the pressure-tight reservoir is divided into a liquid space and a gas space and the pressure-tight reservoir has liquid and gas inlet tubes and an outlet stub, and wherein the device is provided with at least one control means for regulating the pressure in the gas space and the temperature in the liquid space of the reservoir. Pre- ferred embodiments of the device according to the invention are described in Claims 7 to 10.

Further details of the solutions according to the invention are discussed in relation to the attached drawings, wherein - Figure 1 shows schematically an embodiment of the device for producing ice of gel consistency (ice jelly) according to the invention in a sectional view;

- Figure 2 illustrates the pressure-temperature profiles to be applied when the ice jelly is produced;

- Figure 3 shows the cooling curves of the ice jelly as a function of time at atmospheric pressure [curve (a)] and at the pressures of 5 bar [curve (b)] and 10 bar [curve (c)];

- Figure 4 shows a preferred embodiment of the device according to the invention suitable for producing icy products, in particular beverages, of arbitrary taste or appearance through the addition of various food additives to the ice jelly prepared;

- Figure 5 illustrates graphically the change in the freezing point as a function of super- cooling of the water-based liquid, particularly water; and

- Figure 6 shows a (optionally world- wide) network of devices producing ice jelly according to the invention that is suitable for providing consumers e.g. with the possibility of exchanging recipes with each other via appropriate communication channels in order that they could enjoy a broad spectrum of icy products producible by means of the device according to the invention in their own homes.

Figure 1 shows an embodiment of the device for producing ice jelly according to the invention schematically in cross section. The central unit of the device is a pressure -tight reservoir 1 , which is closed by lid 3 in an airtight manner when the device is assembled. The wall of the reservoir 1 is formed to be suitable for the cooling of the inner volume of the reservoir 1. In one of the preferred embodiments, cooling channels 2 are formed in the wall of the reservoir 1 through which a cooling medium (not shown in the figure) set to an appropriate temperature flows in the course of operation. In another embodiment,

the inner volume of the reservoir 1 can be cooled by a cooling medium arranged externally in a heat exchanging position to the wall of the reservoir 1. To the reservoir 1, preferably at its upper portion, a liquid inlet tube 4 and a gas inlet tube 5 are connected. The inlet tubes 4, 5 are equipped with valves 4a, 5a for regulating the feed of the water-based liquid and that of the (non-oxidant) pressure intensifying gas, preferably carbon dioxide and/or nitrogen, respectively. The valves 4a, 5 a can be one-way valves of suitable construction. Furthermore, an outlet stub 6 equipped with a valve 6a under control is connected to the reservoir 1.

The inner volume of the pressure-tight reservoir 1 is divided into two parts, to a gas space 9 and to a liquid space 10. The gas space 9 is filled with gas through the gas inlet tube 5 by operating valve 5 a. The liquid space 10 is filled with water-based liquid through the liquid inlet tube 4 by operating valve 4a. The outlet stub 6 serves for racking/tapping/dispensing the overpressurized liquid product by operating the valve 6a. The device is also equipped with a pressure gauge 8 for the continuous monitoring of the pressure prevailing in the gas space 9, and with a thermometer 7 for the continuous measurement of the temperature of the water-based liquid within the liquid space 10. The valves 4a, 5 a, the thermometer 7 and the pressure gauge 8 are preferably connected electrically to a control unit (not shown in the figure).

For operating the device in Fig. 1, i.e. for producing ice jelly, water-based liquid is fed into the reservoir 1 through the tube 4, whereas pressure intensifying gas, preferably carbon dioxide and/or nitrogen is fed into the reservoir 1 through the tube 5. This phase I is shown in Fig. 2, wherein the pressure is Pi and the temperature is T ₁ . In the following phase II, the gas continuously fed increases the initial (tipically atmospheric) pressure Pi within the reservoir 1 to a second pressure P ₂ . Under the increasing pressure, the gas fed is absorbed (to an ever increasing degree) in the water-based liquid, and as a result of the absorption the liquid gets saturated with the gas at the temperature Ti maintained in reservoir 1. Simultaneously with the saturation, temperature Ti is decreased to a temperature T ₂ determined experimentally by having the cooling medium flown through the cooling channels 2. The liquid can be stored indefinitely in phase III by maintaining the parameters (T ₂ , P ₂ ) constant. After that, in phase IV, the second temperature T ₂ and pressure P ₂ values are changed: on the basis of the parameters determined experimentally for

achieving the gel consistency, the pressure of the water-based liquid oversaturated with the gas within the reservoir 1 is modified to a third pressure P ₃ (tipically atmospheric or near to that) at the outlet stub 6 when the liquid is dispensed, and in the meantime, the water-based liquid reaches a third temperature T ₃ . The formation of ice jelly occurs at this third pressure P ₃ , determined by the tapping rate depending on the difference between the third pressure P ₃ and the second pressure P ₂ in combination with the cross section of the outlet stub 6 (see the straight and the dashed lines of phase IV in Fig. 2). It should be noted that in a preferred embodiment of the device for producing ice jelly, the difference between the pressures P ₃ and P ₂ is at most 15 bar, preferably at most 10 bar, and the cross section of the outlet stub 6 is at most 3 cm ² , preferably at most 2 cm ² . The nucleation centres are formed by the tiny gas bubbles leaving the solution, which due to their homogeneous distribution within the volume of the liquid being just dispensed result in ice of homogeneous structure, i.e. ice jelly. Setting of the system to phases characterized by the different pressure-temperature values can be accomplished by arbitrary external regulating units (not shown in the drawings).

Curves (a), (b) and (c) in Fig. 3 show the experimentally measured decrease in the freezing point as a function of time, when a gas with an overpressure of 1 bar (normal state), 5 bar and 10 bar is applied, respectively. The curves show how supercoolability of the wa- ter-based liquid (in the present case, pure water) changes in time at the given pressures, and after supercooling in what time and at what temperature the liquid containing the dissolved gas freezes (this latter is specified by the plateaus of the curves). At a pressure of 5 bar [curve (b)], the liquid reaches in about 90 seconds a point which means not the formation of ice, but a supercooled state in which the water-based liquid is in between a liquid and a solid state, i.e. it has a gel consistency. The gel consistency appears at a temperature of -0.3 ⁰ C and lasts for about 60 seconds, then the liquid freezes. At a pressure of 10 bar, the liquid is supercooled to -4 ⁰ C which is reached in about 100 seconds. The gel consistency already mentioned maintains for about 30 seconds (see the plateau of curve (c)), then the liquid freezes. At this point the temperature of the gel is -1.3 ⁰ C.

We note here that the observed phenomenon can probably be observed not only in the case of water, but also with every liquid that shows a volume reduction when subjected

to a phase transition from the solid to the liquid state (i.e. at melting). Of course, the gas pressures and the supercooling temperatures required for the production of a desired ice jelly may not be the same for water-based liquids of different compositions.

The application of higher pressures is advantageous if the object is to dissipate more heat from the end product. In addition, when higher pressures are applied, more ice jelly is formed in the process. The experiments revealed that by applying higher pressures, a higher degree of supercooling can be achieved, and parallel to this, it is possible to produce ice jelly in larger amounts. According to the experiments, in the exemplary case of water saturated with carbon dioxide, the supercooling temperature is sufficient for reaching the state of gel consistency under study in every case; thus according to the present example at a pressure of 5 bar the supercooling temperature is -0.3 ⁰ C, whereas at a pressure of 10 bar it is -1.3 ⁰ C. Nevertheless, for the production of ice jelly in significant amounts, the optimal pressure value is at least 5 bar. The essential parameters ensuring the accomplishment of the process according to the invention are provided by the plateaus of the curves shown in Fig. 3.

Figure 4 illustrates a further possible embodiment of the device for producing ice jelly according to the invention, which is suitable for the preparation of beverages according to arbitrary recipes after producing the ice jelly through mixing it with various food additives. The main component of the embodiment shown in Fig. 4 is a reservoir 51 having a liquid inlet tube 54 provided with a controlled dispensing valve Sl, a gas inlet tube 55 provided with a controlled dispensing valve S2 and an outlet stub 56 provided with a controlled dispensing valve S7, wherein the reservoir 51 encloses a gas space 61 and a liquid space 62. The tube 54 is in connection with the gas space 61, whereas the tube 55 and the outlet stub 56 communicate with the liquid space 62. Cooling of the liquid space

62 is performed by a cooling unit 52 under control. In addition, a secondary cooling unit

63 is inserted downstream on the outlet stub 56 before the dispensing valve S7 which serves for the after-cooling of the ice jelly produced. To ensure the physical parameters needed, the dispensing valves Sl, S2, S7, the cooling unit 52 and the optional secondary cooling unit 63 are controlled by a control unit 64 which is equipped with a communication unit 65 for transmitting data to further ice jelly producing or other devices (e.g. a computer). In addition, to make gas absorption and heat exchange more efficient, the res-

ervoir 51 can also be provided with an electric mixer 53, although the usage of such an additional unit, due to its costs, can be justified useful and as a must only for producing ice jelly on an industrial scale.

The main feature of the embodiment according to the invention shown in Fig. 4 is that it is suitable for preparing ice jelly in a closed system according to a prescribed recipe chosen by the consumer and ,,enriched" with various food additives, such as specific flavours, colouring agents, odorants and so on, that is, an icy beverage from the ice jelly (so-called raw jelly) produced previously by it. For this purpose, the device is provided with an arbitrary number of (in practice, usually at most ten to twelve separate pieces of) additive storage vessels which can be cooled separately (see elements 57 to 60). These storage vessels contain e.g. sweeteners, various kinds of flavouring substances, colouring agents or odorants, etc., and are connected to the downstream section of the outlet stub 56 located after the dispensing valve S7 through suitable tubings and dispensing valves (see elements S3 to S6) inserted into the latter. The control of the dispensing valves at issue is also carried out by the control unit 64 in conformity with the wish of the consumer that was previously inputted into the control unit 64 in a certain way (e.g. by means of a data input effected through a touch screen or a keyboard not shown in the drawings).

It should be noted that in the solutions according to the present invention no external means or influence are exploited for commencing the nucleation process necessary for the ice jelly production. To achieve a state of gel consistency, the pressure and the temperature of the gas are regulated, and for this such data related to the gas absorption capacity of the water-based liquid used as a basis are used that are obvious to a person skilled in the relevant field. If the water-based liquid contains various additives, the gas absorption, the temperature, the temperature gradient and the parameters for the gel state naturally change, however, the changes do not influence the fact of gel state formation, as the additives mentioned are subsequently added to the ice jelly after its leaving the reservoir, i.e. when it has been dispensed.

Figure 5 shows the experimentally measured freezing point as a function of supercooling.

It can be seen in Fig. 5 that at the applied pressure values lower freezing point can be achieved when higher supercooling is applied. In turn, higher supercooling results in a

larger amount of ice jelly formed. In the embodiment shown in Fig. 4, the extent of supercooling can be regulated by the secondary cooler 63 and the control unit 64.

The system shown in Figure 6, i.e. the network of ice jelly producing devices comprises a data layer A including an user authentication and database management system 101, a media storage 102, as well as a database management system 103; a firewall 104; an application server layer B including servers 105 for running logically the application for serving and coordinating the requests of users and further systems; a web service layer C including a unified messaging server 106 for handling different types of messages (e- mail, SMS, MMS, and M2M messages), a mobile information server 107 serving as an interface to the mobile communication devices, as well as a web server 108 for serving Internet based requests; an access network D including an Internet and LAN network 109, a mobile access network 110 and a wireless (WiFi, WiMax) network 111; and an end-user layer E including a consumer 112, an ice jelly designer 113, a computer 114 equipped with a web browser, a mobile phone 115 and device(s) 116 for producing ice jelly.

The ice jelly designer 113 and the consumer 112 log in to the ice jelly network through making use of mobile phones 115 or devices 116 for producing ice jelly by providing their user names and passwords. The user authentication and database management system 101 carries out their authentications and provides an access for them to the data stored in the media storage 102 and in the database management system 103, as well as to the resources at the application servers 105 for logically running the application. The user interfaces and messages are provided by the unified messaging server 106, the mo- bile information server 107 and/or the web server 108. The user interfaces are transmitted to the users and then back through one of the access network D, e.g. the Internet and LAN network 109, the mobile access network 110 and/or the wireless network 111. The recipes created by the ice jelly designer 113 are stored in the database management system 103 in such a manner that every formulation receives an individual code. From here the formulations are downloaded by the consumers 112 and the device(s) 116 for producing ice jelly from the database management system 103 via the built-in TCP/IP connection by providing the individual codes, on the basis of which the ice jelly producing devices 116 produce the proper end product which corresponds to the formulation ere-

ated by the users. Consumption of end products prepared on the basis of the recipes requires no authentication, said products can be downloaded from the database management system 103 by any user or consumer 112. However, the ice jelly designers 113 and the users are limited to edit merely the recipes of their own creation.

The individual elements of the network of ice jelly producing devices can be installed/placed in various restaurants, places of amusement, or private houses, and these elements are in connection with the central systems formed by layers A to E. By means of the ice jelly designer 113 the consumers 112 are capable of creating their own formu- lations from the various flavouring substances and can save them into the database management system 103.

In what follows, referring to Figures 3 and 6 the operation of the ice jelly producing network is discussed.

When the system is put to operation, the reservoir 51 is filled up with about 10 to 15 litres of water/water-based liquid which is cooled to a temperature between -1 to +1 ⁰ C by the cooling unit 52. In the meantime, carbon dioxide is absorbed in the liquid at a pressure of 6 to 10 bar. The temperature of the secondary cooling unit 63 is also adjusted to a temperature between -1 to +1 ⁰ C by the cooling unit 52. The consumers 112 select the recipe identified by an individual code in the database management system 103, then this code is inputted through the keyboard of the ice jelly producing device 116. After that, the device 116 gets into contact with the database management system 103, downloads the recipe selected, and - corresponding to the value selected earlier - adjusts the tem- perature of the secondary cooling unit 63 to a temperature between -5 to -7 ⁰ C, while opens the valve S7. When the water-carbon dioxide mixture reaches the secondary cooling unit 63 its pressure is about 6 to 10 bar, and within the secondary cooling unit 63 its temperature rapidly changes to a temperature between -2 to -4 ⁰ C. After this, the pre- cooled additives in accordance with to the recipe selected are added to the mixture in ar- bitrary proportions, preferably from 0 to 20-25 volume% by using the valves S3 to S6. In extreme cases, additives in a greater amount can also be used. The mixture thus formed leaves the system through the outlet stub 56, while the second pressure changes tipically to atmospheric pressure, and at the same time the outflowing liquid gets into a state of gel

consistency after the carbon dioxide has left. The addition of the additives takes place in the last second, thus they also form further nuclei as far as the formation of carbon dioxide bubbles is considered. As a consequence, carbon dioxide leaves the liquid in a much larger amount thereby catalyzing the formation of ice jelly. At the end of tap- ping/dispensing, the secondary cooling unit 63 is switched off and warms back to about a temperature of about -1 to +1 ⁰ C due to the liquid flowing through it. The amount of liquid removed at tapping is fed back to the reservoir 51, while the temperature and the pressure are adjusted to values between -1 to +1 ⁰ C and 6 to 10 bar, respectively.

In the process according to the invention, ice jelly formation takes place in a manner determined by the tapping rate which, in turn, depends on the combined effects of the overpressure and the cross section of the outlet stub 56. Furthermore, the gel consistency of the product is achieved neither in the reservoir nor in the vessel for dispensing, but directly at the free end of the outlet stub 56.

If the materials used in the production process are edible, the ice of gel consistency (ice jelly) produced according to the invention is suitable for human consumption. The ice of gel consistency can also contain organic and inorganic additives enabling the usage of the ice jelly in other fields too, such as e.g. as cooling medium in cooling systems. The sim- plest preparation mode of ice jelly is by using water and carbon dioxide. In this case, an icy product similar to other frozen consumer goods, e.g. ice creams, is obtained but with a smaller weight and a simpler structure. Compared to other icy consumer goods, a further advantage is that to the production there is no need to make use of additional additives facilitating freezing or jellying, and furthermore no mechanical agitation is needed or no external energy input is required for commencing the nucleation process. The state of gel consistency is achieved by controlling the temperature and the pressure with a knowledge of the liquid-gas system desired.