IT201900016292A1 - Apparatus and method for creating vacuum in food containers - Google Patents

Description

Apparatus and method for creating vacuum in food containers

DESCRIPTION

The present invention relates to an apparatus for creating vacuum in food containers.

The invention is also directed to a method for creating a vacuum carried out with the aforementioned equipment.

The invention finds particular, albeit not exclusive, application in all those areas in which it is required to create a predetermined degree of vacuum inside food containers, and in particular in containers containing food having a temperature above 58 ° C. The reference to this temperature is linked to the fact that, regardless of the conditions or operating phases for which the vacuum food container is intended, the possibility of bacterial proliferation in the food is avoided and to allow a considerable reduction of the oxygen concentration. in the air in contact with food thanks to the evaporation of the water contained in it.

Non-limiting examples of fields of application of the invention are, for example, those relating to the hot preservation of cooked foods, or the vacuum cooking of food or the concentration of vacuum foods due to the evaporation of the water contained.

By way of example only, it should be considered that the food contained inside the aforementioned containers can be of different types, for example it can be a soup or a minestrone, a roast, stewed meat, sauce, jams, concentrates for example of tomato or it can comprise more complex preparations with more ingredients.

Furthermore, in general, the containers of the aforementioned type can assume two distinct main configurations: In a first configuration, the container consists of a plastic bag, inside which vacuum is applied with vacuum pumps.

The bags must meet certain requirements, including:

● must be suitable for food use (they must not release substances that are hazardous to health),

● they must withstand the pressure created by the vacuum during its creation phase,

● they must withstand the temperature both during a possible cooking phase and for the entire duration of any storage period, ● they must be weldable or equipped with a valve on which the vacuum can be applied and suitable for maintaining it throughout the conservation phase, ● they must not be permeable to oxygen and little or no permeable to water.

In a second configuration, the container can be for example a pan or a pot or it can simply have a cylindrical shape like that of a vase and can be made of metal, glass or plastic.

The container must comply with some requirements, including:

● it must be resistant to the degree of vacuum to which it is intended to be subjected and to the temperature of any cooking and / or storage, ● it must be equipped with a lid resistant to the degree of vacuum required and a valve on which to apply the vacuum which must then close to keep it and with the possibility of being opened at the end of the storage period to break the vacuum and proceed to open the lid. Furthermore, the lid must be equipped with a gasket (generally made of silicone material) to seal the container once the vacuum has been created.

If the container is a pot, this can be equipped with heating systems (for example electric resistances, magnetic induction system, water steam system) and a temperature control system to maintain the temperature of the food at its level. internal to the desired value. It can also be equipped with a mechanical stirring and homogenization system.

With reference to the case where the vacuum application is carried out after the food has been cooked in the container or during cooking or concentration at temperatures below 100 ° C, it is generally preferable that the vacuum is applied to the container at temperatures above 58 ° C. This prevents the temperature from dropping in an area where bacterial proliferation is possible. This is one of the advantages of the so-called heat preservation method.

Systems for creating vacuum based on vacuum pumps are known (for example piston or vane pumps, lubricated or non-lubricated). These systems are used to create a certain degree of vacuum even very high (for example, reaching pressures of a few millibars) inside the containers. Since food is present inside the containers and this food always has a non-negligible and often very high water content, the physical limit to which the air pressure can be reduced is the vapor pressure of the water at the temperature at which the food is located.

Consider, for example, the following values of the water vapor pressure at some temperatures:

The vacuum creation pumps, as prescribed by their manufacturers, cannot work with foods that are too hot, for example with foods with temperatures above 60 ° C, not so much for the degree of vacuum which is limited by the vapor pressure of the water. which at 60 ° C is equal to 200 mbar, but because at those temperatures during the vacuum phase there is a high evaporation of water and organic substances which then condense on the colder surfaces of the pipes and / or filters and / o of the valves and / or inside the vacuum pump creating problems of clogging, lubrication and possible bacterial contamination.

Due to these obvious limitations, simple and economical applications are not known to date which provide for vacuuming containers containing foods that are at temperatures above 58 ° C. In fact, if vacuum pumps are used, to avoid fouling and bacterial contamination problems, it is necessary to use liquid ring pumps with a constant flow of water and in any case to equip the system with a washing system.

A main object of the present invention is to provide an apparatus for creating vacuum in food containers, structurally and functionally designed to overcome the limits highlighted with reference to the cited known art.

This and other purposes that will emerge below are achieved by the invention by means of an apparatus and a method operating with this apparatus, achieved in accordance with the attached claims.

The features and advantages of the invention will better emerge from the detailed description below of a preferred example of embodiment illustrated, by way of non-limiting example, with reference to the accompanying drawings in which:

- Figures 1 and 2 are perspective views of respective examples of food storage containers suitable for the application of vacuum through the equipment of the invention,

- Figure 3 is a schematic view in longitudinal section of an ejector device of the apparatus of the invention,

- figure 4 is a schematic side elevation view of the device of figure 3,

Figure 5 is a schematic side elevation view of the device of Figure 3 shown in combination with a food container of the type shown in Figure 2,

Figure 6 is a schematic view of a variant embodiment of an ejector suitable for the application of the method of the invention shown in combination with a compressed air supply line. With reference to the aforementioned figures, an apparatus made in accordance with the invention is designed for creating vacuum in a food container 1.

The food, indicated with C, contained in the container 1 to which a certain level of vacuum is applied, must be, for the reasons mentioned above, at a higher temperature of 58 ° C.

The container 1 has an overall volume partly occupied by food and partly occupied by the air in contact with the food.

As will be fully described below, the container 1 can have different conformations, all suitable to be operationally combined with the apparatus of the invention, for example it can be a plastic bag (figure 1) or it can be a pan or a pan with substantially rigid structure and designed to be closed by a lid 2 (Figure 2). In both cases, the container delimits inside an overall volume occupied partly by food and partly by the air in contact with the food.

In the following, reference will be made to the container 1 having the shape of a pan or a pot with a lid, but it is understood that the equipment is to be considered equally usable in the event that the container assumes the shape of a flexible plastic bag.

The temperature of the food inside the container should generally not be below 58 ° C, in order to avoid deterioration due to bacteriological action.

For the application of the vacuum, the equipment includes an ejector device 10 operating with compressed air. An example of an ejector 10 that can be used to apply the vacuum to the container is shown in Figure 3. It is of the type comprising an inlet section 11 for the flow of compressed air, from which a tubular portion extends, terminating in a nozzle 12 adapted to accelerate the flow. air flow conveyed into the ejector. Downstream of the nozzle 12 there is a chamber 13 in communication with a suction duct 14. A divergent duct 15 also extends in correspondence with the chamber 13, ending in an outlet section 16, through which the flow of compressed air mixed with the fluid sucked through the duct 14 flows thanks to the depression created in the chamber 13 due to the Venturi effect induced. from the passage of the compressed air flow through the nozzle (converging section) and the diverging section of the ejector.

Reference 17 indicates a silencer element possibly provided downstream of the outlet section 16.

Reference 18 indicates a suction cup structure, provided at the attachment section of the suction duct 14, which is suitable for ensuring the connection of the ejector to the container, with a seal in the area of air intake from the container. For applications in which the container is a pot, the suction cup can be conveniently replaced by a pipe (for example flexible) connected to the lid through, for example, a quick coupling.

A flow of compressed air (the pressure of which can for example be chosen in the range 5-7 bar) is delivered to the ejector 10 through the inlet section 11 (for example by connecting this section to a compressed air line) and creates a vacuum in the chamber 13 before exiting the outlet section 16 by dragging with it a flow of air sucked by the duct 14 which is in communication with the chamber 13. By thus connecting the attachment section 14a of the duct 14 to the closed container 1, it is possible to create inside it a certain degree of vacuum which depends on the characteristics of the ejector (geometry and dimensions in particular), on the pressure and flow of the compressed air entering the section 11, and on the time of application of the vacuum.

It should be noted that one of the advantages of using an ejector of the aforementioned type for creating vacuum in containers such as the one in figure 5 with inside the food having high temperatures (higher than 58 ° C) is that, not having the organ ejector in motion, there are no lubrication problems and any fouling problems are limited:

● to the area of chamber 13 inside the ejector where the depression produced by the compressed air flow is created

● to duct 14 where the vacuum is created

● to the diverging tubular outlet portion 15

● to any silencer 17 positioned downstream of the outlet section 16.

Cleaning of the group consisting of the ejector 10, the silencer 17 (if present) and the suction cup 18 is easily done, for example:

● placing the unit in a dishwasher, ● washing the unit by hand with the use of detergents suitable for the purpose,

● letting the compressed air flow from the connection 11 and immersing the suction cup 18 in a container containing a solution of a liquid with antibacterial action and collecting the liquid spray that comes out from the outlet section 16 or from the silencer 17, if any This is not applicable in the case of pots where the piping is rigidly fixed to the lid or to the pot itself.

It is also provided that in correspondence with the inlet section 11 there is a connection 11a for connecting the ejector to the compressed air line, and said connection 11a is conveniently a "quick connection", i.e. easily detachable without the aid of equipment details, so that even the kitchen staff can easily remove it and clean the unit following the appropriate instructions provided by the manufacturer.

It is understood that once a preselected degree of vacuum has been reached in the container, the container 1 is closed and sealed to prevent the achieved vacuum from being altered.

If the container is a plastic bag, the step of sealing the bag can be conveniently carried out by heat sealing.

Furthermore, a valve 22 is integrated in the bag, suitable for creating and sealing the vacuum in the bag.

If the container is shaped like a pan or pot with relative closing lid, the lid and / or pan or pot are provided with a sealing gasket 23 designed to ensure vacuum seal between pan or pot and lid during vacuum creation phase, and during any subsequent operational phases (for example during a possible subsequent cooking, or during a subsequent phase of hot preservation of the food).

Furthermore, the cover 2 is provided with a valve 24 suitable for creating and sealing the vacuum.

With reference to Figure 5, it is provided that the ejector 10 is applied to the lid of the container by means of the suction cup 18, so that the valve 24 of the lid remains inside the suction cup structure.

With regard to the ejector 10, it is envisaged that the flow of compressed air delivered to it can be controlled by a control unit (schematically represented in figure 7 and marked with 25).

In an embodiment, the control unit is configured to regulate the compressed air flow rate through the control of a first solenoid valve 26 located upstream of the air inlet section 11 in the ejector or through the direct control of an air compressor. (not shown) designed to generate compressed air to be delivered to the ejector. In this last case, the ejector is powered by compressed air generated by an air compressor connected directly to the ejector power line, therefore without the need to use a compressed air tank.

The use of a compressed air flow to create the vacuum has the further advantage of mixing the vapors of water and any organic substances that are sucked from the container during the vacuum creation phase with the compressed air, limiting or eliminating the condensation problems of these vapors and helping to disperse them in the air. In fact, these vapors of water or organic substances in themselves do not create problems in the kitchen because they are the same vapors that are released from the container after cooking but could create major problems if concentrated because they could condense in contact with colder air or on cold surfaces and this is what happens if vacuum pumps are used, in line with the solutions of the prior art.

Another advantage of creating a vacuum when the food is at temperatures above 58 ° C, in addition to not going into the bacterial proliferation zone, is that steam production is exploited during the vacuum process. of water evaporated from the food to bring the oxygen concentration in the container to much lower values than the vapor pressure of the water. In fact, the production of steam inside the container during the vacuum creation phase has the effect of "washing" the volume of air present in the container, continuously reducing, for the duration of the vacuum application, the concentration of oxygen.

For example, if an ejector is used that can reach, by its constructive nature, a vacuum degree of 100 mbar and a container that contains a food at a temperature of 80 ° C, with the ejector it will be possible to obtain an absolute pressure. in the container, for example, of 350-400 mbar which is a little lower, but not by much, than the 473 mbar which is the vapor pressure of water at 80 ° C. This slightly lower value of the vapor pressure is due to the cooling of the food during the water evaporation process and the fact that the water in the food is not present in pure form. It should be considered that the amount of water that must evaporate to obtain low oxygen concentration values even in a large volume pan or pot (for example 10-20 liters) is not very high and is limited to a few cubic centimeters of water. In fact, every cubic centimeter of evaporated water produces about 1 liter of steam and a few liters of steam are enough to "wash" the air in the container and bring the oxygen concentration to very low values. For example, after 1 minute of vacuum application, oxygen concentration values below 0.1% can easily be reached. Obviously, the final value depends not only on the temperature of the food and the volume of the container but also on the performance of the ejector and the consumption of compressed air: with the same degree of vacuum that can be reached, generally an ejector that consumes more compressed air, will suck a flow rate of more air than that sucked in by an ejector which consumes less, with the final result of evaporating more water, therefore “washing” more and therefore lowering the oxygen concentration more.

To understand the advantage of applying vacuum with food at temperatures above 58 ° C, consider that, if the container and the food had been at a temperature of 20 ° C (instead of 80 ° C) and the vacuum had been created at that temperature with the same ejector, with the same pressure and flow rate of the inlet compressed air and for the same time, the effect of water evaporation would have been negligible (at 20 ° C the vapor pressure is equal to only 23 mbar) and the final vacuum level would have been about 100 mbar (instead of 350-400 mbar). However, since there was no significant evaporation of water (and therefore no "washing"), the oxygen concentration of the air in contact with the food in the container would have been about 20.9 * 100/1013 = 2.1% 20.9 being the volumetric percentage (%) of oxygen in the atmospheric air, 100 mbar the pressure reached at the end of the vacuum phase and 1013 mbar the atmospheric pressure. An oxygen concentration of 2.1% instead of 0.1% can be a problem due to oxidation reactions that have a high impact on the organoleptic characteristics of the food.

The parameters that influence the oxygen concentration that can be obtained at the end of the vacuum formation process are therefore:

● type of food,

● amount of food,

● food and container temperature,

● type of container (for example pan and lid and therefore its volume),

● type of ejector and in particular the degree of vacuum it can reach,

● pressure and flow rate of compressed air,

● duration of the vacuum process,

Once all these parameters have been set, to be sure that the desired oxygen concentration has actually been reached, it would be necessary to measure it.

Measuring the oxygen concentration directly (for example with the use of Lambda probes) can be very expensive and presents many problems, for example due to the delicacy of the probe, the problems related to its insertion and management and the difficulty of calibrating these sensors.

The trend of the degree of vacuum (absolute pressure) over time is a valid alternative to the direct measurement of the oxygen concentration as it can be directly correlated to the oxygen concentration that occurs at the end of the vacuum process once the aforementioned parameters have been set.

A solution, therefore, to the problem of ensuring that at the end of the vacuum process a certain concentration of oxygen has been reached, can be that illustrated in figure 7, in which the use of a pressure gauge 27 is envisaged, which measures the pressure in the area of the chamber 13 which is substantially equal to the depression created by the ejector in the intake duct 14.

In one embodiment, the vacuum degree measurement is carried out manually by means of a pressure gauge of the analog type. In a further embodiment, the measurement of the degree of vacuum in the container is carried out by means of a pressure transducer, said transducer being connected to a control unit, for example to the control unit 25, configured to process the pressure signal generated by the transducer.

It can also be envisaged that the duration of the vacuum application in the container is a function of the measured vacuum degree.

In an embodiment example, the control of the vacuum generation time in the container involves the following steps:

- set a minimum temperature of the food in the container,

- create a predetermined degree of vacuum within a first predetermined time interval,

- maintaining said vacuum degree for a second predetermined time interval.

The durations of the vacuum generation and maintenance times of the vacuum degree during the operation of the ejector can be controlled and decided by the operator, in the case of a manual measurement, or, alternatively, they can be controlled and decided by the control unit. control, if a pressure transducer is operatively associated with the control unit.

With reference to figure 6 and to some applications such as the preservation of hot food, the ejector 10 is also provided with a second quick coupling 28 for connection to an air line which carries the pressure signal to the meter 27, so as to make the ejector easily and quickly removable from said line, without the aid of special equipment, so that even the kitchen staff can easily remove it and clean it.

The air line that connects the ejector to the pressure gauge 27 is also connected to the compressed air network via a second solenoid valve 29.

Figure 6 shows how the ejector 10 is connected to a compressed air line 30, through a pipe 31 that carries the solenoid valve 26 upstream to connect it to the compressed air supply line 30. Figure 6 also shows the solenoid valve 29 for connecting a pipe 32 of the compressed air line 30 to the line connected to the pressure gauge 27 and to the area of the chamber 13 of the ejector 10. This solenoid valve 29 is used to flush in the pipe 32 clean compressed air for a few seconds before the end of the vacuum phase, thus obtaining two results:

1) the pipe 32 is cleaned by letting out any droplets of condensation that may have formed during the vacuum formation phase

2) the valve 24 closes quickly and hermetically. In other words, said solenoid valve 29 is opened at the end of the vacuum creation phase for a limited time (a few seconds) so as to allow compressed air to flow into the duct that connects the pressure gauge to the ejector.

As also emerged from the above description, the invention is directed to a method for generating vacuum inside a container in which the food is at a temperature higher than at least 58 ° C, the method providing for the application of the vacuum by means of an ejector device operating with compressed air and having a suction duct capable of connecting with the container for the generation inside it of a preselected level of vacuum.

The method, more specifically, provides that the generation of a selected level of vacuum inside the container in which the food is at a temperature above at least 58 ° C, is applied with the equipment having the characteristics described above.

The invention thus achieves the proposed purposes by achieving the advantages stated with respect to the solutions of the aforementioned prior art.

Claims (1)

CLAIMS 1.Equipment for generating vacuum inside a container containing food at a temperature above at least 58 ° C, comprising an ejector device for the application of vacuum operating with compressed air and having a suction duct capable of connection with the container for the generation inside it of a selected vacuum level. 2. Apparatus according to claim 1, wherein the container is a plastic bag. 3. Apparatus according to claim 2, wherein a valve is integrated in the bag, suitable for creating and sealing the vacuum in the bag. 4. Apparatus according to claim 1, wherein the container is a pan or pan provided with a closing lid. 5. Apparatus according to claim 4, in which the lid and / or the pan or pan are provided with a sealing gasket suitable for guaranteeing the vacuum seal between the pan and the lid during the vacuum creation phase. 6. Apparatus according to claim 5, wherein the lid is provided with a valve suitable for creating and sealing the vacuum. 7. Apparatus according to one of the preceding claims, in which the ejector is provided with a first quick coupling for connection to a compressed air line, so as to make the ejector easily and quickly removable from the compressed air line. 8. Equipment according to one of the preceding claims, in which the ejector is powered by compressed air generated by an air compressor connected directly to the ejector power line, without the provision of a compressed air tank. 9. Equipment according to one of the preceding claims, in which the flow rate of compressed air delivered to the ejector is controlled by a control unit. 10. Apparatus according to claim 9, wherein the control unit is configured to regulate the compressed air flow rate through the control of a first solenoid valve located upstream of an air inlet section in the ejector or through the direct control of a air compressor designed to generate compressed air to be delivered to the ejector. 11. Apparatus according to one of the preceding claims, in which the measurement of the degree of vacuum created in the container is provided. 12. Apparatus according to claim 11, in which the measurement of the vacuum degree is carried out manually by means of a pressure gauge of the analog type. 13. Apparatus according to claim 11, wherein the measurement of the vacuum degree in the container is carried out by means of a pressure transducer, said transducer being connected to a control unit configured to process the pressure signal generated by the transducer. 14. Apparatus according to one of claims 11, 12, wherein the ejector is provided with a second quick coupling for connection to an air line which carries the pressure signal to the meter, so as to make the ejector easily and quickly removable from said line. 15. Equipment according to one of claims 11, 12, in which the air line connecting the ejector to the pressure gauge is connected to the compressed air network via a second solenoid valve. 16. Apparatus according to claim 15, in which it is provided that said second solenoid valve is opened at the end of the vacuum creation phase for a time of a few seconds so as to let compressed air flow in the duct that connects the pressure gauge to the ejector. 17. Equipment according to one of the previous claims in which the air intake section in the ejector is provided with a suction cup for connecting the ejector with the container. 18. Method for generating vacuum inside a container in which the food is at a temperature above at least 58 ° C, the method providing for the application of the vacuum by means of an ejector device operating with compressed air and carrying a suction capable of connecting with the container for the generation inside it of a preselected vacuum level. 19. Method for generating vacuum inside a container in which the food is at a temperature above at least 58 ° C, the selected vacuum level being applied with an equipment according to one or more of claims 1 to 17.