Apparatus for freezing and storing consumer goods and method for freezing and storing consumer goods

Abstract

An apparatus for storing consumables, comprising an inner housing disposed within an outer insulated housing, the walls of the inner housing defining a compartment for receiving the consumables, the walls including an inlet wall for allowing heat exchange fluid to enter the compartment, an opposing outlet wall for allowing heat exchange fluid to exit the compartment, side walls and a base, the side walls and base being adjacent to the inlet wall and outlet wall, the inlet wall and outlet wall each including a series of openings for accommodating a continuous flow of heat exchange fluid through the apparatus so that, in operation, consumables received in the compartment of the inner housing are immersed in the heat exchange fluid and exchange heat with the heat exchange fluid.

Description

[Technical Field]

[0001] The present invention relates to a method for freezing consumables and an apparatus for storing consumables. [Background technology]

[0002] Food preservation by refrigeration is widely used in domestic and commercial environments. The product's temperature is reduced to a level that slows all deterioration processes, such as chemical and enzymatic reactions, and microbial growth. Typically, enzymatic reactions, such as lipase activity, can be stopped by blanching the product prior to freezing.

[0003] Available home refrigeration systems are designed to balance operational costs with the appropriate freezing temperature to extend product shelf life. The temperature ranges of these systems are predetermined and cannot be easily changed by the user. Additionally, many home freezers feature upright displays, which provide easy consumer access but can reduce cooling efficiency.

[0004] Commercial freezing systems include liquid nitrogen individual quick freezing (IQF) systems, liquid nitrogen immersion systems, and air blast freezing. Some of these technologies can achieve high heat transfer coefficients, kill microorganisms, and allow direct contact with the food, but all result in poor sensory outcomes (taste, texture, appearance) and are typically only suitable for low-value products.

[0005] While the preservative benefits of freezing food are well known, existing methods can result in quality degradation. The primary quality loss is changes in texture and taste, often due to dehydration of the outer layers of the product. Another problem is "drip loss," which occurs when ice crystals grow within the product, puncturing cell walls and allowing juice to escape, resulting in a loss of mass upon thawing. This results in a loss of firmness, nutritional value, and flavor. The rate of ice crystal growth is exacerbated by slow freezing processes and repeated freeze-thaw cycles, which cause fluid to move from the interior of the cells to the exterior. Rapid freezing minimizes water migration from the interior of the cells, promoting the formation of smaller intracellular ice, resulting in less tissue damage and drip loss and a more homogeneous structure. Cryogenic freezing systems are frequently used in the biomedical field to preserve cells for later use. The cryopreservation process generally consists of two major steps: 1. Controlled Cooling and Preservation of Cells In this step, the liquid is removed from the cells and replaced with a cryoprotectant, after which they are placed in a controlled liquid nitrogen bath to achieve vitrification. 2.Long-term storage in liquid nitrogen The cells stored under controlled cooling are placed in a liquid nitrogen storage tank and kept for several years or as long as needed.

[0006] IQF technology and liquid nitrogen immersion systems for food preservation are widely based on the second stage, but as mentioned above, this process is not only inefficient but can also damage the product. First stage is not commonly used as a solution for preserving food because the food cannot have its liquid removed and replaced with a cryoprotectant.

[0007] Furthermore, food phase transitions are highly relevant to the quality of preserved foods. Glass, being non-crystalline, has a disordered structure similar to that of a liquid or amorphous state. In the glassy state, compounds involved in deterioration can only diffuse very slowly across intermolecular distances. Therefore, foods below the glass transition temperature can remain highly stable for months or even years. Because foods are composed of multi-component mixtures, predicting their overall properties is difficult, and glass transition temperatures are typically reported for pure components rather than the actual food. This presents an ongoing challenge in the field of food preservation, where consistent and accurate data are lacking and difficult, if not impossible, to achieve. Summary of the Invention [Problem to be solved by the invention]

[0008] In this context, there is a need for a reliable method of food preservation by freezing that successfully balances a) the need to achieve a target temperature that results in the reduction or elimination of microorganisms, b) the freezing rate required to reduce ice crystal formation and thereby cell damage, and c) economic viability.

[0009] While immersion tanks exist for freezing food products, previous systems have had problems with the high viscosity of the fluid at low temperatures and keeping the fluid isolated from organic contaminants. When packaging is used to contain the food and prevent contamination, the packaging tends to tear or otherwise become damaged during rapid cooling processes, including freezing by liquid nitrogen processes.

[0010] Improved systems are needed to preserve consumable goods (e.g., fish, meat, milk, etc.) in a cost-effective manner that maintains the integrity of the original food, including reducing adverse effects on taste and nutritional value, and enhances product safety. [Means for solving the problem]

[0011] According to a first aspect of the present invention, there is provided an apparatus for storing consumables comprising an inner housing disposed within an outer insulated housing, the apparatus being characterized in that the walls of the inner housing define a compartment for receiving the consumables, the walls including an inlet wall for allowing heat exchange fluid to enter the compartment, an opposing outlet wall for allowing heat exchange fluid to exit the compartment, side walls and a base, the side walls and base being adjacent to the inlet wall and outlet wall, each of the inlet wall and outlet wall including a series of openings for accommodating a continuous flow of heat exchange fluid through the apparatus so that, in operation, consumables received in the compartment of the inner housing are immersed in the heat exchange fluid and exchange heat with the heat exchange fluid.

[0012] According to a second aspect of the present invention, there is provided a method of storing consumables in a storage device using a heat exchange fluid, the method comprising: a. determining the total surface area of ​​the approximate shape of the consumable to be frozen; b. performing a computational fluid dynamics analysis of the consumables within the device based on flow constraints imposed by both the tank geometry and the predetermined placement of the food product within the tank, and the predetermined temperature rise of the heat exchange fluid; c. determining the heat transfer coefficient of the consumable material at a given product surface temperature; d. selecting the lowest heat transfer coefficient determined in step c by rounding down to the nearest 10; e. dividing the approximate shape of the consumable into a predetermined number of equal volumetric increments; f. estimating the thermal properties of the consumable; g. calculating the time required for each increment to reach a predetermined final temperature from a predetermined initial temperature for a predetermined heat exchange fluid temperature and a predetermined flow rate of the heat exchange fluid based on an energy conservation analysis using the heat transfer coefficient determined in step d; h. determining an average rate of cooling achievable based on the time calculated in step f; i. selecting a predetermined heat exchange fluid temperature if the determined average rate of achievable cooling is equal to or greater than 0.5°C per minute, and if the determined average rate of achievable cooling is less than 0.5°C per minute, selecting a heat exchange fluid temperature sufficiently below the predetermined heat exchange fluid temperature such that the achievable cooling rate is at least 0.5°C per minute; j. placing consumables within the device for storage; k. exposing the consumable to cooling using the temperature determined in step i, cooling the consumable at a rate of at least 0.5°C per minute; It has.

[0013] The total surface area may be that of a simplified geometric estimation of the consumable item, for example, a milk bottle may be approximated as a cylinder, and therefore the total surface area would be the total surface area of ​​those cylinders.

[0014] A consumable may be, for example, a food product such as fish, meat, vegetables, etc. A consumable product may also consist of a liquid product such as a beverage or liquid ingredient, such as milk. Consumable, as used herein, may also refer to the product that is consumed in addition to its packaging, such as a bottle, plastic film, etc.

[0015] Preferred embodiments of the methods and devices disclosed herein can minimize ice crystal formation and prevent cell damage during storage.

[0016] Preferred embodiments of the methods and devices disclosed herein provide preservation without the use of any sugars or synthetic additives.

[0017] Preferred embodiments of the methods disclosed herein provide sublimation-free preservation of consumables.

[0018] Preferred embodiments of the methods and apparatus disclosed herein provide reduced drip loss compared to conventional refrigeration.

[0019] Preferred embodiments of the methods and apparatus disclosed herein provide for the preservation of consumables in a manner that preserves nutritional value and maintains or improves product safety compared to fresh products.

[0020] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a bottom perspective view of a consumable product storage tank. [Figure 2] FIG. 2 is a top perspective view of a tank for storing consumables. [Figure 3] FIG. 3 is a top perspective view of a tank that contains milk bottles. [Figure 4] FIG. 4 is a top perspective view of a tank containing trays for fish or meat. [Figure 5] FIG. 5 is a top perspective view of a tank containing trays for fish or meat. [Figure 6] FIG. 6 is a top perspective view of the tank including an empty basket for containing baby bottles. [Figure 7] FIG. 7 is a top perspective view of the bottle basket. [Figure 8] FIG. 8 is a top perspective view of a rack for holding trays of meat or fish. [Figure 9] Figure 9 is an individual tray for holding meat or fish. [Figure 10] Figure 10 is an image showing the results of a computational fluid dynamics analysis of the temperature inside a tank containing 100 one-liter bottles of milk. [Figure 11] Figure 11 is an image showing a computational fluid dynamics analysis of the flow velocity within the tank. [Figure 12] FIG. 12 is a conductivity top view of the analysis shown in FIG. [Figure 13] Figure 13 is a cut plot between rows of bottles showing the temperature distribution within the tank. [Figure 14]Figure 14 is a cut plot through a row of bottles showing the temperature distribution within the tank. [Figure 15] Figure 15 is a cut plot through the row of bottles showing the velocity distribution in the tank. [Figure 16] FIG. 16 is a graph showing the relationship between the specific enthalpy of whole milk and temperature. [Figure 17] FIG. 17 is a graph showing the conductivity of milk. [Figure 18] FIG. 18 is a graph showing the temperature decrease over time for 11 equal increments for the first case of storing milk. [Figure 19] FIG. 19 is a graph showing energy levels over time for a first case of storing milk. [Figure 20] FIG. 20 is a graph showing the temperature decrease over time for 11 equal increments for a second case of storing milk. [Figure 21] FIG. 21 is a graph showing energy levels over time for a second case of storing milk. [Figure 22] FIG. 22 is a graph showing the temperature decrease over time for 11 equal increments for a third case of storing milk. [Figure 23] FIG. 23 is a graph showing the change in energy level over time for a third case of storing milk. [Figure 24] FIG. 24 is a graph showing the temperature decrease over time for 11 equal increments for a fourth case of storing milk. [Figure 25] FIG. 25 is a graph showing energy levels over time for a fourth case of storing milk. [Figure 26] FIG. 26 is a graph showing the relationship between the specific enthalpy of fish and temperature. [Figure 27] FIG. 27 is a graph showing the conductivity of fish products. [Figure 28] FIG. 28 is a graph showing the temperature decrease over time in 11 equal increments for the first case of preserving fish. [Figure 29]FIG. 29 is a graph showing energy levels over time for the first case of preserving fish. [Figure 30] FIG. 30 is a graph showing temperature reduction over time in 11 equal increments for a second case of preserving fish. [Figure 31] FIG. 31 is a graph showing energy levels over time for a second case of preserving fish. [Figure 32] Figure 32 is an image showing the results of a computational fluid dynamics analysis of the temperature inside a tank containing meat. [Figure 33] Figure 33 is an image showing a computational fluid dynamics analysis of velocities in a tank containing meat. [Figure 34] Figure 34 is a cut plot through a tray of meat showing the temperature distribution within the tank. [Figure 35] Figure 35 is a cut plot through a tray of meat showing the velocity distribution within the tank. [Figure 36] FIG. 36 is a graph showing temperature reduction over time in 11 equal increments for a third case of preserving fish. [Figure 37] FIG. 37 is a graph showing energy levels over time for the third case of preserving fish. [Figure 38] FIG. 38 is a graph showing temperature reduction over time in 11 equal increments for the fourth case of preserving fish. [Figure 39] FIG. 39 is a graph showing energy levels over time for the fourth case of preserving fish. [Figure 40] FIG. 40 is a graph showing the relationship between the specific enthalpy of meat and temperature. [Figure 41] FIG. 41 is a graph showing the conductivity of meat products. [Figure 42] FIG. 42 is a graph showing the temperature decrease over time in 11 equal increments for the first case of preserving meat. [Figure 43] Figure 43 is a graph showing energy levels over time for the first case of preserving meat. [Figure 44] Figure 44 is a graph showing temperature reduction over time in 11 equal increments for a second case of preserving meat. [Figure 45] Figure 45 is a graph showing energy levels over time for a second case of preserving meat. [Figure 46] FIG. 46 is a graph showing temperature reduction over time in 11 equal increments for a third case of preserving meat. [Figure 47] Figure 47 is a graph showing energy levels over time for a third case of preserving meat. [Figure 48] FIG. 48 is a graph showing temperature reduction over time in 11 equal increments for a fourth case of preserving meat. [Figure 49] Figure 49 is a graph showing energy levels over time for a fourth case of preserving meat. [Figure 50] FIG. 50 is a piping and instrumentation diagram of a refrigeration system. DETAILED DESCRIPTION OF THE INVENTION

[0022] Immersion Tank Figures 1 and 2 show an immersion tank 1 for storing consumer goods. In this example, the immersion tank 1 is shown filled with bottles and has a capacity for up to 100 milk bottles. The tank 1 is constructed of steel to conform to ASTM A240. The tank 1 has two heat exchange fluid inlets 2 and two heat exchange fluid outlets 3, with the inlets 2 located on the inlet wall 4 and the outlets 3 located on the outlet wall 5. Figure 2 shows an inner housing 10 located inside the outer wall of the tank 1. The inner housing 10 has an inlet wall 14, an outlet wall 15, and a base 16, each containing openings 11 that allow the heat exchange fluid to flow in and out of the inner housing 10. The openings 11 are provided in four rows of ten openings each in the inlet wall 14 and the outlet wall 15, and in ten rows of ten openings each in the base 16. The openings 11 in the inlet wall 14 and the base 16 are 10 mm in diameter, and the openings 11 in the outlet wall 15 are 20 mm in diameter. The inlet wall 14 is located 100 mm from the inner surface 12 of the inlet 2, thereby providing a gap 13. A similar gap is provided between the outlet wall 15 and the inner surface of the outlet wall 5. A further 100 mm gap is provided at the base. The inner surface 12 is defined by a steel formwork located 50 mm from the inlet 2 and secured with brackets, providing a cavity into which polyurethane foam insulation is pressed during the manufacture of the tank 1. Insulation is provided in a similar manner on all four walls of the tank, from the top of the tank to approximately 595 mm below the tank wall. A row of 30 mm diameter holes 22 is provided along the bottom of each wall, along strips 23 positioned at an angle of approximately 45° between the base 7 and the tank wall. The strips 23 are provided to support the tank structure and can also be used as guides to prevent the trays or baskets from resting against the wall or base of the inner housing 10. It will be understood that other arrangements that reinforce the tank structure and provide a guiding function are also possible. The holes 22 help to reduce stagnation of heat exchange fluid that may build up in these areas of the tank due to the presence of the strips 23 .

[0023] A drain 6 is provided from the base 7 of the tank 1 and is formed as an elbow pipe directed to extend beyond the outlet wall 5 of the tank 1 below the heat exchange fluid outlet 3. The heat exchange fluid inlet 2 and heat exchange outlet 3 have a diameter of 80 mm.

[0024] Tank 1 further includes a lid formed of steel plate (not shown). Tank 1's base 7 includes four central legs 8 that support the tank's central weight, and legs 16 located at the corners of the tank and formed at the edges of the tank wall. The lower edge of the tank wall has cutouts 9 to provide access for maintenance of tank base 7. Tank 1 is configured in a square shape with a height of approximately 1.105 m and a side length of 1.705 m. When freezing milk, as shown in FIG. 3, a structure consisting of a bottle basket 17 is suspended from the lid (not shown) by a bar 18 with hooks on opposite ends, and bar 18 can be attached to the lid by mounting parts 19.

[0025] As shown in FIG. 4, a structure consisting of a rack tray 21 of 40 kg can be suspended from a lid for storing meat or fish.

[0026] Figure 5 is a top perspective view showing a meat / fish rack tray 21 within the tank 1. Figure 6 shows a bottle basket 17 within the tank 1. The bottle basket 17 includes receiving holes 20 for holding the sides of bottles.

[0027] 7 shows bottle basket 17 in isolation. Basket 17 has base 24 and opposing sides 30. Sides 30 are attached to opposite ends of bars 18 that will be attached to the lid via mounting portions 19. Bottle stabilizer portions 20a, which include bottle receiving portions 20, are attached to basket 17 by clipping into slots 31 in opposing sides 30. Additional holes 20b are provided between bottle receiving portions 20 to facilitate fluid flow between the bottles when basket 17 is filled with bottles and immersed in a heat exchange fluid.

[0028] 8 shows the meat / fish rack tray 21 in isolation. The rack tray 21 also includes opposing sides 30 into which the individual trays 28 can clip with slots 31. The individual trays 28 are each closed with a latch 25. The rack trays 21 hang from opposing ends of the bar 18 and are attached to the underside of the tank lid by mounting points 19. A user can grasp the handles 29 to slide the individual trays 28 out of the rack tray 21.

[0029] Figure 9 shows an individual tray 28 in isolation, which has shaped sections 26 for enclosing individual pieces of meat or fish, which close around hinge joint 27 and are secured by latches 25.

[0030] Tank 1 is filled with a heat exchange fluid that will not freeze at temperatures above -70°C. The heat exchange fluid is pumped into tank 1 through heat exchange fluid inlet 2 into void 13 at a volumetric flow rate of 17 cubic meters per hour. As the heat exchange fluid is forced through the restricted area of ​​opening 11, pressure builds up in void 13, thus decreasing the volumetric flow rate but increasing the velocity of the fluid entering inner housing 10. Some fluid also travels under inner housing 10 and up into the opposing cavity in outlet wall 5, while some fluid also travels upward through openings 11 in base 7 of inner housing 10. Openings 11 improve distribution of the cool fluid throughout the tank (see, for example, Figure 10, which shows the temperature distribution throughout the tank) and minimize the occurrence of hot spots that would otherwise occur away from the inlet area. As the heat exchange fluid flows continuously through the tank 1, heat is removed from the milk and milk bottles, and the heated heat exchange fluid exiting the tank 1 is then exchanged with a refrigeration system which continuously cools the heat exchange fluid. The heat exchange fluid itself exchanges heat with the refrigerant in the refrigeration system.

[0031] Preferably, a low-temperature heat transfer fluid is used as the immersion fluid for the tank, which advantageously has a relatively low viscosity even at cryogenic temperatures, which in turn can reduce the pump power requirements for the system. The table below (Table 1) defines some of the thermal properties of heat transfer fluids.

[0032] [Table 1]

[0033] At each of the above temperatures, the heat exchange fluid has a density that is very low and less than the density of water. In the event of any breakage or spillage during operation of the tank, the broken or spilled material will tend to sink to the bottom of the tank, preferably allowing the material to be easily drained without substantial loss of heat exchange fluid. It will be appreciated that any suitable heat exchange fluid may be used, provided that it has a low enough viscosity that excessive pumping power is not required at the low temperatures required for storage. Preferably, the heat exchange fluid is also food-safe.

[0034] [Table 2]

[0035] Table 2 above provides the temperature difference between the tank inlet and outlet for various heat exchange fluid flow rates, assuming 20 kW of heat is extracted from the fluid in the tank. From Table 2, it can be seen that a 3°C temperature difference between the inlet and outlet can be achieved using a mass flow rate of approximately 4 kg / s. This temperature difference was determined to be an acceptable temperature rise in light of the required evaporator duty and the required product cooling. The acceptable temperature rise must be balanced against the costs associated with the maximum number of products that can be processed at one time to make the system commercially viable. It is understood that a higher flow rate is desirable to increase heat transfer between the heat exchange fluid and the consumables. However, a higher flow rate also increases flow resistance, requiring higher pump power.

[0036] Computational fluid dynamics analysis of milk A computational fluid dynamics analysis is performed on the tank to visualize how the heat exchange fluid flows through the tank, estimate the heat transfer coefficient between the heat exchange fluid and the consumables, and determine the pressure drop as the heat exchange fluid flows through the tank.

[0037] Figure 10 is a side view showing a simulated flow analysis of the heat exchange fluid in a tank when the bottle surface temperature is specified as -30°C. The figure is shaded to represent the temperature at various points in the tank, with black representing the warmest zone and white representing the coldest zone. The arrows show the trajectory of the fluid moving through the tank and around the bottle. The cold fluid at 50°C can surround the bottle due to distribution through the opening 11. As can be seen in this figure, the heat exchange fluid enters the tank at approximately -50°C through the inlet wall, which is on the left side of the tank in this illustration. As the heat exchange fluid absorbs heat from the consumer product (in this case, the milk bottle), slightly warmer heat exchange fluid, approximately -47°C, accumulates at the top of the tank before exiting through the outlet wall. A 3°C increase in the temperature of the heat exchange fluid was allowed.

[0038] Figure 11 shows a side view of a simulated flow analysis of the heat exchange fluid in the tank for the same example, but the illustration is shaded to represent the various flow velocities. The flow velocity in the tank around the milk bottle is very small, i.e., less than 0.02 m / s. However, higher flow velocities can be seen at the inlet wall (left side of the image), at the various openings in the bottom, and at the openings in the outlet wall (right side of the image) as the fluid passes through the openings.

[0039] FIG. 12 is a top view of the tank under the same conditions as in FIGS. 10 and 11, with the temperature distribution shaded.

[0040] Analysis of similar processes at various other bottle surface temperatures produced the following table (Table 3) showing the average heat transfer coefficients determined between the milk (including the bottle) and the heat exchange fluid.

[0041] [Table 3]

[0042] The flow rate of the heat exchange fluid was set very low, so that the convective heat transfer from the bottle to the heat exchange fluid was largely driven by the natural motion of the fluid caused by local heating of the fluid and the corresponding density difference, i.e., buoyancy-driven flow. The pressure drop from the inlet to the outlet was found to be about 660 Pa at a flow rate of 4 kg / s.

[0043] Heat transfer analysis for milk Further analysis is performed by investigating the effect of varying the input parameters of the refrigeration system. This may include product geometry, product temperature, packaging characteristics, and the characteristics of the racking system utilized. In this method, the consumable is divided into geometric units (e.g., the cylindrical shell of a bottle). This means that at a given time step, a certain amount of energy is removed from a shell, resulting in a decrease in the temperature of that shell. The amount of energy removed is a function of the temperatures of adjacent shells and the resistance to heat flow between them. Therefore, the thermal properties of the consumable as a function of temperature must be taken into account.

[0044] The analysis was performed assuming that milk could be treated as a solid mass with a starting temperature of 2°C and properties given in the ASHRAE Engineering Handbook - Refrigeration, Thermal Properties of Foods (including protein, fat, and water content). Figure 16 plots the specific enthalpy values ​​of whole milk at different temperatures obtained from the handbook. Figure 14 is a graph showing the conductivity of whole milk measured by the Kopelman method.

[0045] A number of cases were investigated to evaluate different geometries of milk bottle products and different temperatures of the heat exchange fluid. The table below (Table 4) provides an overview of the cases investigated.

[0046] [Table 4]

[0047] Considering the results obtained from the computational fluid dynamics analysis shown in Table 3, the heat transfer coefficient was estimated to be 130 W / m by taking the lowest simulated heat transfer coefficient and rounding it down to the nearest 10. 2 ·K. The table below (Table 5) shows the freezing time predicted by the simulation software for the cases investigated above.

[0048] [Table 5]

[0049] Figure 18 shows the temperature-time relationship for the investigated case 1 at 11 geometrically uniformly distributed increments from the bottle surface to the core. As can be seen from Figure 18, a rapid temperature drop is observed in the outermost layer of the bottle within the first 5 minutes, while no significant temperature drop is observed in the core until approximately 41 minutes. Furthermore, it takes approximately 43.5 minutes for the center temperature to reach -30°C. This result suggests that ice crystal formation was minimized.

[0050] Figure 19 shows the total enthalpy over time for the investigated case study 1 compared to the energy levels at average product temperatures of -10°C and -30°C, respectively. These target temperatures, -10°C and -30°C, were selected as relevant targets based on many factors. For example, microbial activity is killed or slowed at different temperatures depending on the microorganism, and the rate and duration of cooling at the target temperature vary. In particular, storing food at -10°C for several days is lethal to certain microorganisms, such as Toxoplasma gondii, Entamoeba, and Trypanosoma brucei. However, to be commercially viable, this temperature must be achieved within a reasonable time frame, and rapid freezing is required to minimize cellular damage due to ice crystal formation. The values ​​selected balance economics, cellular damage (resulting in sensory deterioration of the food), and microbial destruction and / or delay.

[0051] It was determined that the refrigeration system would need to preserve 100 one-liter bottles of milk starting at 4°C and bring them to a final temperature of -30°C within 35 minutes.

[0052] The mass of the milk is calculated to be 103.8 kg. The specific enthalpy of milk at 4°C is 369 kJ / kg The specific enthalpy of milk at 30°C is 18.5 kJ / kg The required energy removal from milk is given by the following formula: m(h initial -h final ) (1) where: m = mass of milk h initial = initial specific enthalpy of milk (at 4°C) h final = Final specific enthalpy of milk (at -30°C)

[0053] Therefore, the amount of heat removed from milk is 103.8(369-18.5)=36382(kJ). If the freezing time is 35 minutes, the required heat removal rate is 36382 / (35(mins)×60(secs))=17.3(kW).

[0054] Assuming that 1 kW of heat is obtained from the atmosphere, the required duty of the refrigeration system is 18.3 kW. Since freezing milk places the highest load on the refrigeration system, it must be able to freeze at least 100 bottles of 1 liter of milk in 35 minutes, i.e., it must have a specification of at least 18.3 kW. Therefore, the initial design condition for the refrigeration system is an evaporator duty of 20 kW, including a safety margin of 1.7 kW. The tank inlet temperature can be either -50°C or -70°C.

[0055] Returning to Case 1, a glass milk bottle with a diameter of 85 mm has an inlet temperature of -50°C, a flow rate of 4 kg / s, and a heat transfer coefficient of 130 W / m 2 The glass outer layer is 1 mm thick and is cooled by a heat exchange fluid with a temperature of 0.15°C.

[0056] Figure 20 shows the temperature profile at equal increments for Case 2. In this case, the milk is contained in a glass bottle with a diameter of 85 mm, a thickness of 1 mm, and a volume of 1 liter. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 130 W / m 2 ·K.

[0057] Figure 21 compares the energy calculated over time for the energy levels that result in an average product temperature of -10°C and -30°C for the investigated case 2.

[0058] Figure 22 shows the temperature profile at equal increments for Case 3. In this case, the milk is contained in a PET bottle with a diameter of 69 mm, a thickness of 1.5 mm, and a capacity of 500 mL. The heat exchange fluid has an inlet temperature of -50°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 130 W / m. 2 ·K.

[0059] Figure 23 compares the energy calculated over time for the three cases investigated, with the energy levels resulting in an average product temperature of -10°C and -30°C, respectively.

[0060] Figure 24 shows the temperature profile at equal increments for Case 4. In this case, the milk is contained in a plastic bottle with a diameter of 69 mm, a plastic thickness of 1.5 mm, and a capacity of 500 mL. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 130 W / m. 2 ·K.

[0061] Figure 25 compares the energy calculated over time for the investigated case 4, with the energy levels resulting in an average product temperature of -10°C and -30°C, respectively.

[0062] As can be seen from a comparison of Figures 18, 20, 22, and 24, there is no significant difference in freezing time between the 85mm diameter bottle and the 69mm diameter bottle. It can be seen that the 1.5mm thick plastic bottle has higher heat resistance than the 1mm thick glass bottle. The surface area of ​​the 500mL bottle is significantly smaller than that of the 1000mL bottle.

[0063] Heat transfer analysis of fish

[0064] [Table 6]

[0065] The starting temperature of the fish was also 2°C. The fish type was cod and its physical properties were taken from the ASHRAE Engineering Handbook - Refrigeration, Thermal Properties of Foods. Figure 26 shows the specific enthalpy values ​​obtained for the fish. Figure 24 shows the conductivity values ​​obtained for the fish.

[0066] Considering the results obtained from the computational fluid dynamics analysis shown in Table 6, the heat transfer coefficient was estimated to be 100 W / m, which was obtained by rounding down the lowest simulated heat transfer coefficient below 10. 2 ·K.

[0067] Examples of surveys conducted on fish are shown in the table below (Table 7).

[0068] [Table 7]

[0069] As shown above, the flow rate of the heat exchange fluid, and therefore the heat transfer coefficient (HTC), remains the same for each of the above cases. The table below (Table 7) shows the results of the freezing time predicted by the simulation software for the above investigated cases.

[0070] [Table 8]

[0071] For each of the above cases, the temperature change over time is calculated at 11 equal increments from the surface to the core of the fish. Figure 28 shows the temperature profile for Case 1. In this case, the fish is 50 mm thick, 100 mm long, and 50 mm wide. The fish is encased in 0.1 mm plastic. The inlet temperature of the heat exchange fluid is -50°C, the mass flow rate is 4 kg / s, and the heat transfer coefficient is 100 W / m. 2 ·K.

[0072] Figure 29 compares the energy calculated over time for the investigated case 1 at the energy levels that result in an average product temperature of -10°C and -30°C.

[0073] Figure 30 shows the temperature profile for Case 2. In this case, the fish is 50 mm thick, with a length and width of 100 mm and 50 mm, respectively. The fish is encased in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m 2 ·K.

[0074] Figure 31 compares the energy calculated over time for the energy levels that result in an average product temperature of -10°C and -30°C for the investigated case 2.

[0075] Figure 36 shows the temperature profile for Case 3. In this case, the fish is 25 mm thick, 100 mm long, and 100 mm wide. The fish is encased in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -50°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m 2 ·K.

[0076] Figure 37 compares the energy calculated over time for the investigated case 3, at the energy levels that result in an average product temperature of -10°C and -30°C, respectively.

[0077] Figure 38 shows the temperature profile for Case 4. In this case, the fish is 25 mm thick, 100 mm long, and 100 mm wide. The fish is encased in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m. 2 ·K.

[0078] Figure 39 compares the energy calculated over time for the investigated case 4, at the energy levels that result in an average product temperature of -10°C and -30°C, respectively.

[0079] As can be seen from the above results, thin fish pieces can be frozen faster than thick fish pieces.

[0080] Heat transfer analysis for meat The starting temperature of the meat was also assumed to be 2°C. The meat type was lean sirloin, and its physical properties were taken from the ASHRAE Engineering Handbook - Refrigeration, Thermal Properties of Foods. Figure 40 shows the specific enthalpy values ​​obtained for the fish. Figure 41 shows the conductivity values ​​obtained for the fish.

[0081] Examples of meat surveys are shown in the table below (Table 9).

[0082] [Table 9]

[0083] As shown above, the flow rate of the heat exchange fluid, and therefore the heat transfer coefficient (HTC), remains the same for each of the above cases. The table below (Table 10) shows the freeze time results predicted by the simulation software for the above investigated cases.

[0084] [Table 10]

[0085] For each of the above cases, the temperature change over time is calculated for 11 equal increments from the surface to the core of the meat. Figure 42 shows the temperature profile for Case 1. In this case, the meat is 50 mm thick, 100 mm long, and 50 mm wide. The meat is encased in 0.1 mm plastic. The inlet temperature of the heat exchange fluid is -50°C, the mass flow rate is 4 kg / s, and the heat transfer coefficient is 100 W / m 2 ·K.

[0086] Figure 43 compares the energy calculated over time for the investigated case 1 at the energy levels that result in an average product temperature of -10°C and -30°C.

[0087] Figure 44 shows the temperature profile for Case 2. In this case, the meat is 50 mm thick, with a length and width of 100 mm and 50 mm, respectively. The meat is contained in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m 2 ·K.

[0088] Figure 45 compares the energy calculated over time for the investigated case 2, at energy levels that result in average product temperatures of -10°C and -30°C, respectively.

[0089] Figure 46 shows the temperature profile for Case 3. In this case, the meat is 25 mm thick, 100 mm long, and 100 mm wide. The meat is encased in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -50°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m 2 ·K.

[0090] Figure 47 compares the energy calculated over time for the three cases investigated, with the energy levels resulting in an average product temperature of -10°C and -30°C, respectively.

[0091] Figure 48 shows the temperature profile for Case 4. In this case, the meat is 25 mm thick, 100 mm long, and 100 mm wide. The meat is encased in 0.1 mm plastic. The heat exchange fluid has an inlet temperature of -70°C, a mass flow rate of 4 kg / s, and a heat transfer coefficient of 100 W / m 2 ·K.

[0092] Figure 49 compares the energy calculated over time for the investigated case 4, at the energy levels that result in an average product temperature of -10°C and -30°C, respectively.

[0093] As can be seen from the above results, thinner pieces of meat can be frozen faster than thicker pieces of meat.

[0094] In a preferred embodiment of the present invention, the consumables are contained within a package or within a basket or tray structure that is used for immersion in the tank, which advantageously prevents sublimation of the product during the preservation process, a problem with existing immersion preservation methods that do not use packaging due to cracking issues.

[0095] Advantageously, using the above analysis, the device can be used to reduce the temperature of a food product to a target temperature (e.g., -50°C) at a desired flow rate (e.g., 4 kg / sec) in a desired time (e.g., 30 minutes). The input parameters of the device are set based on the analysis results. This allows the user to simply select the product (e.g., fish fillets) when using the device. It is preferable to use thin packaging with minimal air gaps, such as vacuum packs or heat-shrink packaging.

[0096] While theoretical freezing rates of 10°C per minute or 100°C per minute may result in even greater reduction in microbial levels in consumables and less cell damage, such rates are not feasible for commercial freezing systems. Moreover, it has surprisingly been found that slower cooling rates, such as about 1°C per minute, can achieve significant levels of microbial reduction while retaining high sensory quality and preventing damage to the packaging.

[0097] Although the heat transfer analysis in the above examples was performed for 11 volume increments of each consumable food product, it will be understood that this number can be varied.

[0098] The table below shows the results for milk stored for a 45 minute cooling period to a temperature of -30°C immersed in a heat exchange fluid at -50°C, the results are said to be similar to a pasteurisation process.

[0099] [Table 11]

[0100] Refrigeration system FIG. 50 is a piping and instrumentation diagram of a refrigeration system that continuously cools a heat exchange fluid.

[0101] The refrigeration system includes a heat exchanger for exchanging heat between a heat transfer fluid and a refrigerant, which may be R404A.

Claims

1. An apparatus for preserving a consumable product by freezing the consumable product, the apparatus comprising an inner housing disposed within an outer insulated housing, the inner housing having an air gap therebetween; a wall of the inner housing defining a compartment for receiving a consumable product, the wall including an inlet wall for allowing a heat exchange fluid to enter the compartment, an opposing outlet wall for allowing the heat exchange fluid to exit the compartment, a side wall and a base, the side wall and the base being adjacent to the inlet wall and the outlet wall; The outer insulating housing is an inlet side surface corresponding to the inlet wall of the inner housing and defining an inlet space between the inlet side surface and the inlet wall; an outlet side surface corresponding to the outlet wall of the inner housing and defining an outlet space between the outlet side surface and the outlet wall; and the inlet and outlet walls each include a series of openings for accommodating a continuous flow of heat exchange fluid through the device such that, in operation, consumables received in the compartments of the inner housing are immersed in the heat exchange fluid and exchange heat with the heat exchange fluid; the inlet side includes at least one inlet communicating with the inlet space from outside the outer insulating housing; the outlet side includes at least one outlet communicating from the outlet space to the outside of the outer insulating housing; the apparatus further comprising a pump for pumping the heat exchange fluid through the at least one inlet and into the inlet space; In operation, the heat exchange fluid is introduced into the device through the at least one inlet and removed from the device through the at least one outlet. An apparatus characterized in that

2. The device of claim 1 , wherein the base includes a series of openings.

3. a structure receivable within the compartment for holding the consumable product, the structure comprising: a. one or more of a tray, a rack, and a basket; and b. Suspended from the lid of the device 3. The device according to claim 1, wherein the device is at least one of the following:

4. An apparatus as described in any one of claims 1 to 3, characterized in that the inlet space and the outlet space are fluidly connected.

5. An apparatus as described in any one of claims 1 to 4, characterized in that the at least one inlet and the at least one outlet have a diameter of 80 mm.

6. 6. Apparatus according to any one of claims 1 to 5, characterized in that, in use, the apparatus is configured to be connected to an external refrigeration system whereby, in use, a heat exchange fluid exchanges heat with a refrigerant.

7. 1. A method of preserving a consumable product by freezing the consumable product in a storage device using a heat exchange fluid, comprising: a. determining the total surface area of ​​the approximate shape of the consumable to be frozen; b) performing a computational fluid dynamics analysis of the consumables within the device based on flow constraints imposed by both the compartment geometry and predetermined placement of the consumables within the compartment, and the predetermined temperature rise of the heat exchange fluid; c) determining a heat transfer coefficient between the consumable and the heat exchange fluid at a given consumable surface temperature; d. selecting the lowest heat transfer coefficient determined in step c by rounding down to the nearest 10; e. dividing the approximate shape of the consumable product into a predetermined number of equal volumetric increments; f. estimating a thermal property of the consumable; g. calculating the time required for each increment to reach a predetermined final temperature from a predetermined initial temperature for a given heat exchange fluid temperature and a given flow rate of said heat exchange fluid based on an energy conservation analysis using the heat transfer coefficient determined in step d; h. determining the average rate of cooling achievable based on the time calculated in step f; i. selecting the predetermined heat exchange fluid temperature in response to the determined average rate of achievable cooling being equal to or greater than 0.5°C per minute, and selecting a heat exchange fluid temperature sufficiently below the predetermined heat exchange fluid temperature such that the achievable cooling rate is at least 0.5°C per minute in response to the determined average rate of achievable cooling being less than 0.5°C per minute; j) placing the consumable product within the device for storage; k. exposing said consumable to cooling using the temperature determined in step i, cooling said consumable at a rate of at least 0.5°C per minute; A method for providing the above.

8. a. the predetermined flow rate is about 4 kg / s; b. The predetermined final temperature is i. -10°C, and ii. -30°C be either c. The heat transfer coefficient is: i. 130 W / m ２ Being K, and ii. 100 W / m ２ ・Being K Either 8. The method according to claim 7, wherein the method further comprises at least one of the following:

9. The characteristics of the consumable product include: a. specific enthalpy, b. moisture content, c. fat content, and d. Protein content 9. The method according to claim 7 or 8, comprising at least one of the following:

10. A method according to any one of claims 7 to 9, characterized in that the desired amount of time required is less than 30 minutes.

11. 11. The method of any one of claims 7 to 10, wherein the inlet temperature of the heat exchange fluid is -50°C and the outlet temperature of the heat exchange fluid is -47°C.

12. a. the determined average cooling temperature rate is between 0.5°C per minute and 1.5°C per minute, comprising cooling the product at a rate between 0.5°C per minute and 1.5°C per minute; b. the determined average cooling temperature rate is about 1°C per minute, and cooling the product at a rate of about 1°C per minute.

12. The method according to claim 7, wherein the method is any one of the following:

13. 13. The method of any one of claims 7 to 12, wherein a preserved consumable product is produced such that at least one of the following qualities is maintained: taste, texture, and nutrition.

14. 14. The method according to any one of claims 7 to 13, wherein the device is a device according to any one of claims 1 to 6.

15. 7. A method for preserving consumables by freezing them using a device as claimed in any one of claims 1 to 6, characterized in that the heat exchange fluid is continuously cooled by heat exchange with a refrigerant in a refrigeration cycle external to the device.

Images