METHOD AND SYSTEM FOR DEEP VACUUM PACKAGING OF A FOOD PRODUCT WITHOUT COVERING LIQUID

Abstract

A method for deep vacuum packaging of a food product and a system for implementing this method. The food product and at least one additive are placed in a mixing device. The mixing device is evacuated and its contents are mixed to ensure a penetration of the additive(s) in the food product and to outgas the mixture until an absolute pressure is less than or equal to 30 mbar. The temperature of the food product is less than the boiling temperature of the liquid and the additives contained therein at a particular pressure. At least a portion of the mixture cold blanched is packaged in a tight container. The container is optionally pasteurised/sterilized in a short time by controlling the pressure and temperature conditions such that the container does not open or become crushed under the effect of a pressure difference between the inside of the container and the autoclave.

Claims

1-15. (canceled)

16. Method for packaging of a food product, comprising the following successive steps: placing the food product and one or more additives in a mixing device; evacuating the mixing device and mixing its contents to ensure a penetration of the additive(s) in the food product and to outgas a mixture, until an absolute pressure of less than or equal to 30 mbars is reached; vacuum packaging at least a portion of the mixture cold blanched in at least one container, the mixture being at a temperature less than the boiling temperature of water at a pressure used for vacuum packaging of the mixture; after introducing an equal portion of the mixture into a plurality of rigid containers to define a batch, introducing one or more first measurement sensor into at least one of said rigid containers to define a control container, each first measurement sensor comprises a transmitter to transmit measurements performed in the form of communication signals; and after placing said batch in an enclosure, introducing one or more second measurement sensors into the enclosure, the enclosure is connected to a pressure regulator to reduce a pressure of the enclosure, each second measurement sensor comprises a transmitter to transmit measurements performed in the form of communication signals, so as to determine in real time a differential pressure and a temperature in each container of said batch, thereby enabling a monitoring of the packaging of said batch.

17. The method according to claim 16, wherein the placing step places the food product and the additive(s) in a churn outfitted with an evacuating device.

18. The method according to claim 16, wherein the evacuating step is carried out for a predetermined minimum time to ensure destruction of a majority of a nonsporulated bacterial burden of the food product.

19. The method according to claim 16, wherein, before the evacuating step, a temperature of the food product is at a temperature greater than the boiling temperature of water for an evacuation pressure.

20. The method according to claim 16, wherein, at the end of the evacuating step, the mixture so formed is at the absolute pressure between 10 and 25 mbars.

21. The method according to claim 16, wherein in the vacuum packaging step, after introducing said at least portion of the mixture in at least one rigid container, a water-based impregnation liquid is added to each container, a quantity of the water-based impregnation liquid added is equal to a quantity required to form a saturating vapor atmosphere in each container so as to ensure heat exchanges by evaporation or condensation at the absolute pressure prevailing in each container after its closure.

22. The method according to claim 21, wherein the water-based impregnation liquid added represents less than fifteen percent by weight of a total weight of said each container.

23. The method according to claim 22, wherein the water-based impregnation liquid added represents less than five percent by weight of a total weight of the portion introduced into said each container.

24. The method according to claim 16, wherein, before the vacuum packaging step, a fragile ingredient or additive is introduced alone into the mixing device and outgassed alone down to the absolute pressure less than or equal to 30 mbars, the fragile ingredient or additive being previously placed at a temperature lower than +10 C. to prevent a volatilization of certain constituents of aromatic function.

25. The method of claim 24, the fragile ingredient or additive being previously placed at the temperature between 1 C. and +5 C. to prevent the volatilization of certain constituents of aromatic function.

26. The method according to claim 16, wherein each container is a rigid container and wherein the vacuum packaging step further comprises the steps of: for said each rigid container comprising said at least portion, placing said each rigid container with a cover having a tightness seal in the enclosure connected to the pressure regulator to reduce the pressure of the enclosure; maintaining the cover away from an orifice of said each rigid container by a magnetic element to allow gases contained in said each rigid container to escape; progressively placing the enclosure under a vacuum to ensure an evacuation of said each rigid container to the absolute pressure less than or equal to 30 mbars, this progressivity being determined according to an absolute pressure value and the content of said each rigid container; placing the cover over an opening of said each rigid container to compress its tightness seal against the orifice of said each rigid container; and placing the enclosure at an atmospheric pressure and then releasing a pressure exerted on the cover, the connection between the magnetic element and the cover being broken.

27. The method according to claim 16, further comprising the steps of: hermetically closing said at least one container with a cover by reducing the pressure; bringing the content of said at least one container up to a heat treatment temperature greater than or equal to a threshold temperature of pasteurization or sterilization for an exposure time while continually checking the temperature and the pressure prevailing in said at least one container, and a pressure around said at least one container, so as to prevent any early opening thereof during the heat treatment and any degradation of a structure of at least one of the portion contained in said at least one container and said at least one container; cooling the contents said at least one container to a temperature below a cooking temperature of the food product.

28. The method according to claim 27, wherein the cooling step exposes said at least one container to at least one jet of a liquid.

29. The method of according to claim 28, wherein the cooling step exposes said at least one container to said at least one jet of the liquid immediately at the end of the exposure time.

30. The method according to claim 27, wherein the cooling step comprises the steps of: after purging a volume of air contained in the autoclave, exposing each container to at least one jet of a liquid at the heat treatment temperature; recovering at least some of the liquid introduced into the autoclave and mixing the recovered liquid with a cold liquid to lower the temperature of said each container without causing thermal shocks that will damage said each container; and repeating the recovering step until the temperature of said each container is progressively lowered to a temperature less than the cooking temperature of the food product while monitoring in real time the pressure in the autoclave by injection of a pressurized gas flow inside the autoclave to establish a back pressure or by actuating a purge valve of the autoclave.

31. A packaging system for packaging of a food product, comprising: a mixing device to which the food product and one or more additives are placed; a pumping unit to evacuate an interior space of the mixing device and to mix contents of the mixing device to ensure a penetration of the additive(s) in the food product and to outgas a mixture, the pumping unit is configured to attain an absolute pressure in the mixing device less than 30 mbars; a receiving enclosure to receive a rigid container and a rigid cover, to vacuum package at least a portion of the mixture cold blanched in the container, the mixture being at a temperature less than the boiling temperature of water at a pressure used for vacuum packaging of the mixture, the receiving enclosure is connected to a pressure regulator to reduce a pressure of the receiving enclosure and comprises a magnetic element to hold the cover away from an orifice of the container to allow gases contained in the container to escape, the receiving enclosure is outfitted with one or more first measurement sensors, each first measurement sensor comprises a transmitter to transmit measurement signals; a sterilization autoclave outfitted with one or more second measurement sensors, each second measurement sensor comprises a transmitter to transmit measurement signals; wherein after introducing an equal portion of the mixture into a plurality of rigid containers to define a batch in the receiving enclosure, one or more third measurement sensors are introduced into at least one of said plurality of rigid containers to define a control container, each third measurement sensor comprises a transmitter to transmit measurement signals; and a central control unit to receive said measurement signals to monitor in real time physical parameters in at least one of the following: the receiving enclosure, said each container and the autoclave.

32. The package system according claim 31, wherein the central control unit receives said measurement signals to monitor in real time a pressure and a temperature in at least one of the following: the receiving enclosure, said each container and autoclave.

33. The package system according to claim 31, the pumping unit is configured to attain the absolute pressure in the mixing device between 10 and 25 mbars.

34. The packaging system according to claim 31, wherein the autoclave is equipped with a shower system to direct at least one jet of a liquid onto the container after pasteurization or sterilization of its contents in order to cool it down, the autoclave comprises at least one of an assembly to introduce a pressurized gas flow inside the autoclave to establish a back pressure and a remote controlled purge valve of the autoclave.

35. The packaging system according to claim 31, wherein the autoclave comprises a recovery system to recover at least part of the liquid introduced into the autoclave, the liquid is recycled at least partly to the shower system to be introduced once more into the autoclave after mixing with a liquid at a lower temperature contained in a storage tank, the recovery system comprises at least one measurement device to measure a flow rate and a temperature of the recovered liquid to determine a volume of liquid to be re-injected at a lower temperature.

Description

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0116] It will be noted, first of all, that the figures are not drawn to scale.

[0117] FIG. 1 shows a packaging system for the implementing of the method for packaging of a food product containing pieces according to one particular embodiment of the invention.

[0118] FIG. 2 shows the modification of the accelerated heating and cooling ranges, according to the advancement of the vacuum in the container, made possible in the course of technological improvements since the 1920s, a time when pumps were unable to achieve a vacuum lower than 364 mbar in containers, in which ranges it is possible to exploit the saturating vapour state inside the closed container, which state makes it possible to guarantee that all the heat exchanges inside the container occur by condensation or evaporation on the surfaces of the container or the product, which allows the transfer of 54 kcal/gram of evaporated or condensed water (latent heat of boiling/condensation). Thus, one finds that with the gain in range, and thus time, provided by the system which is the object of the present invention, one can now much more quickly leave the classical parboiling zones (37 C. to 55 C.), believed to favour the development of bacterial spores, which constitutes additional safety for semi-preserves. One can thus move up the opening of the autoclaves which generally takes place below 35 C., this making it possible to benefit from slower sterilization equipment, which constitutes a factor limiting the industrial profitability.

[0119] The proposed method adds several steps to the packaging method described in document EP 1 421 001 A1 in the name of the present applicant, consisting in the following: [0120] (a) upstream from the step of evacuating a tight and rigid container containing a food product, in the enclosure described in document EP 1 421 001 A1, the preparing of this food product so that it is already well outgassed and flavoured, by cold blanching it, the operation consisting in making it undergo a cold vacuum churning in a blender, or mixing device, under high vacuum of 10-30 mbars of pressure, this preparation step being especially designed to eliminate all noncondensable gases trapped inside pieces of the food product and until no cavities remain in the product, either because they are flattened by the vacuum or because they are completely refilled with the ingredients themselves, but also to cause any additives introduced such as salts and flavours to penetrate in depth and finally to greatly reduce the bacterial burden by exploding of nonsporulated cells, making it possible to reduce afterwards the heat treatment times by pasteurization or sterilization. [0121] (b) Still upstream from this step of evacuation of the container, adding to at least the portion of the mixture previously obtained and placed in the tight and rigid container a quantity of water well below the quantity of water usually needed to provide a covering liquid for this mixture, the quantity of water being limited here to several grams, such as 30 grams for a container of 1.5 litres containing 700 grams of green beans, the quantity needed to form a saturating vapour atmosphere enabling the heat exchanges to occur thereafter at very low pressure, and for the boiling of water to occur below 30 C., i.e., utilizing the latent heat of evaporation/condensation of the water, making it possible to speed up the heat exchanges. [0122] (c) upstream from this evacuation step, optionally, and in particular for products which are to be cooked, installing in one or more containers of the batch intended to be packaged a set of radio transmission probes making it possible to know, by analogy in real time, the pressure and the temperature in all the containers of this batch; [0123] (d) during the evacuation step as described in document EP 1 421 001 A1, gradually placing the enclosure 1 under a deep vacuum by attaining a pressure in each container of the batch between 10 and 30 mbars, this progressivity being dictated by the aforementioned pressure value and by the nature of the food product packaged in each container and also by the temperature of this product; [0124] (e) during this evacuation step, monitoring and managing the gradual vacuum descent, the vacuum level, and the exposure time of the product to the vacuum with suitable means, for example, with a system of radio transmission probes for pressure and temperature, installed in one or more control cans and in the autoclave oven, these probes being connected to the central control unit provided with a computer program of digital or graphical display and, optionally, an automatic program for managing the increases and decreases of pressure and temperature; [0125] (f) after this evacuation step, optionally, and in particular for products which are to be cooked, organizing the sterilization or pasteurization in a steam autoclave with back pressure, constantly monitoring the difference in temperature and pressure between the inside of each container and the atmosphere of the autoclave oven in which it is located, to prevent any container from opening by virtue of its internal rise in temperature and pressure or from being crushed as a result of excessive pressure in the autoclave, which is achieved by maintaining the difference in pressure between the inside of each container and the autoclave chamber between 300 and 800 mbars for as long as the temperature of the autoclave remains above 90 C., this delicate operation requiring an automated monitoring of the autoclave, making sure that at certain times, depending on the situation, it is not threatened by cavitation if one is using a pump to evacuate its ballast water; [0126] (g) after the evacuation step, optionally, and in particular for products which are to be cooked, rapidly cooling the product in each container after pasteurization or sterilization, preferably with an autoclave whose cooling down is accomplished by a shower at gradually decreasing temperature starting from the sterilization temperature (for example, 121 C.) to attain the cooking end temperature (such as 68 C.) in less than eleven (11) minutes and, if possible, in less than three (3) minutes if one has available a modified autoclave, either with major extension of its exchange surface, or with a continual evacuation of the ballast water, by gradually lowering the pressure in the autoclave and constantly monitoring the difference in temperature and pressure between the inside of each container and the atmosphere of the autoclave oven in which it is located, to prevent any container from opening by virtue of inadequate pressure in the autoclave or from being crushed as a result of excessive pressure in the autoclave, which can be done for example with a system of radio transmission probes for pressure and temperature, installed in one or more control cans and in the autoclave oven.

[0127] It is thus possible to achieve the vacuum goal, after packaging and cooling down, with an absolute pressure of at most 50 mbars at 4 C. in the container as shown by the present invention.

[0128] A major aspect of the invention involves the carrying out of an operation of sterilization or pasteurization treatment of foods, which is done by heating of the container subsequent to its closure. It will be understood that such a treatment involves foodstuffs containing water which is needed to help create a saturating vapour atmosphere and exploit the advantages of the phase change of the water as described above.

[0129] The instantaneous boiling of the water of the products, brought about by the evacuation of the container, produces a supplemental outgassing of the food product and of the inside of the container and guarantees an environment consisting exclusively of water vapour. But the water of the products is not always enough to create enough vapour. The adding of a very limited volume of moisture is thus necessary (approximately 30 g for 700 g of green beans in a container of 1.5 litres) to ensure enough saturating vapour in the container to enable the accelerated heat transfers at the time of sterilization. As a result, the product is protected against any oxidation, whether by direct oxidation or by enzymatic oxidation, and it is not necessary to add liquid to cover it entirely, an operation which tends to commonly result in the dilution of the soluble substances contained in the product.

[0130] Under the effect of the deep vacuum (10 to 30 mbars of absolute pressure) produced in the container, the peripheral tightness seal of the cover is applied hermetically and durably by itself against the mouth of the container, owing to the bowl-like shape of the central part of the cover, which guides the cover in its movement, and owing to the cleanness of the edges of the cover and the mouth of the container, which should have a rolled rim to offer a sufficient contact surface with the cover seal, which should be provided with an annular groove into which the seal is fitted, which should be flexible enough to hug the shapes of the neck of the container and strong enough to withstand the pressure changes intrinsic to the method and the final pressure exerted after cooling down on the seal and which reach around 8 to 12 kg/cm.sup.2 depending on the format of the container, to which pressure is added the pressure of full containers stacked on top during the storage and transport of the finished products.

[0131] In order to achieve the rapid cooling down proposed by the present invention, one can use an injection of water by temperature-regulated water shower, eliminating any internal recycling of the cooling down water in the autoclave, by maintaining in its ballast only a slight quantity of water and evacuating this hot water to an outside storage unit.

[0132] The temperature of the water should be modulated so that it drops gradually from the temperature of pasteurization or sterilization (for example, T.sub.S=121 C.), without differing too much from the temperature of each container in order to avoid heat shocks which are liable to cause them to be crushed, so as to gradually reach a low temperature (such as around 25 C. to 30 C.) in the autoclave, the temperature of each container enabling the end of the cooking of the food product contained in the corresponding container.

[0133] It has been found that the present method makes it possible to economize on up to 90% of the quantities of water customarily used in vegetable preserving and up to 100% of the covering fats normally used in meat pickling, consequently reducing the transport weight by at least 40%.

[0134] For products which are to be cooked, this method ensures a cooling down of the food product contained in the container after pasteurization or sterilization in a time less than 50 to 75% of the time normally observed, that is, in less than 10 minutes at most, and if one has a high-capacity autoclave with heat exchange in less than 2 minutes for a cylindrical container of drum type, containing 1.5 litres with diameter of 153 mm and height of 92 mm.