JPS63219362A - Method for thawing and preserving food - Google Patents

Abstract

PURPOSE:To prevent outflow of drips from a food, suppress deterioration of taste and loss of weight and contrive good maintenance of quality and uniform thawing, by forming an ice film on the surface of a food in closing operation carried out after thawing operation of a frozen food. CONSTITUTION:A frozen food is thawed with humid and cold air at a higher temperature than 0 deg.C and closing operation for forming an ice film on the surface of the food with cold air at a somewhat lower temperature than the icing point is performed. Cold reservation of the food is then carried out with cold air at a lower temperature than 0 deg.C and somewhat higher temperature than the icing point of the food. As a result, outflow of drips from the food can be prevented to suppress deterioration of taste and loss of weight. Quality can be simultaneously kept well and uniform thawing of the frozen food can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for thawing frozen foods, in which frozen foods are thawed using forcedly circulated high-humidity cold air.

(b) Prior art Japanese Patent Application Laid-open No. 115169/1989 discloses a method for thawing frozen items, which is characterized by sucking cold air from a thawing chamber containing frozen items and blowing the cold air onto the frozen items. Specifically, it is stated that the cold air has a temperature higher than O''C (about 3 to 5 degrees Celsius) and is in a high humidity state.

(c) Problems to be Solved by the Invention According to the above-mentioned prior art thawing method, a large amount of drips (gravy) from the frozen food cannot be avoided, leading to a deterioration in taste.
This caused problems such as a loss of weight due to the outflow of drips, leading to a decrease in operating profit.

In view of these problems, the present invention has been developed to reduce the amount of drips from frozen foods, to achieve uniform thawing of frozen foods, and to preserve thawed foods with high freshness. Provide thawing and preservation methods.

(2) Means for solving the problems In order to solve the problems of the above-mentioned prior art, the present invention
Thaws frozen food with higher temperature, humid cold air,
After this, cold air slightly lower than the freezing point of the food is used to form an ice film on the surface of the food, and then the food is kept cold by cold air lower than 0°C and slightly higher than the freezing point of the food. thawing and preserving food.

(*) Function The present invention is capable of reducing the amount of drips from the food by forming an ice film on the surface of the food by the tightening operation performed after the thawing operation. The surface temperature and core temperature of the food gradually reach equilibrium. Further, by performing the cold preservation operation after the tightening operation, thawed food can be preserved with high freshness for a long period of time.

Example) Examples of the present invention will be described below with reference to the drawings. (1)
This is a thawing chamber whose main body is constituted by an insulating box (2) with an open front, and a storage section (3) for frozen food is formed inside the chamber defined by the insulating box (2). In the storage section (3), trays (6) on which frozen foods are placed are arranged in multiple stages in the vertical direction while being supported by slide rails (5) attached to the shelf supports (4). The front opening is closed by a heat insulating door (7) that can be opened and closed.

In addition, there is a humid cold air generation chamber (
8). The cold air generation chamber (8) includes a plate fin type evaporator (11) equipped with a warming heater (9) and a defrosting heater (10), and an air inlet surface (IIA) of the evaporator (11) and an interval. The eliminator (1
2), and a water sprinkler (1) having an injection nozzle (13A) disposed between the evaporator (11) and the eliminator (12) and spraying water toward the air inlet surface (IIA) of the evaporator (11).
3) and two air blowers m (14>) facing the air outlet surface (IIB) of the evaporator (11) are arranged, and the generation chamber (8)
The front of the room is closed by a service door (15) that can be opened and closed.

Therefore, the evaporator (1) disposed in the humid cold air generation chamber (8)
1), a water collector (16) is placed opposite to the lower part near the eliminator (12), the water sprinkler (13), and the blower (14). A water storage tank (17) is provided with an opening at the top closed by a removable lid (17A), leaving an opening at the top.

The other end of a water supply pipe (18) whose one end is connected to an external water supply system and the other end of a return pipe (19) whose one end is connected to the water collector (16) face the opening of this water storage tank (17). As a result, the water storage tank (17) collects the water supplied from the water supply pipe (18) by opening the water supply electromagnetic valve (21) controlled by the water level detection device (20) installed inside. The water recovered from the vessel (16) through the return pipe (19) is stored.

Further, the bottom of the water storage tank (17) and the water sprinkler (13)
are connected by a feed pipe (23) with a pump device (22) interposed therebetween. This pump device (22) is a heat insulating box (
2) is arranged in a machine room (24) defined below, and a drain pipe (25) is branched from the feed pipe (23>) on the outlet side of the pump device (22).This drain pipe (25> The chamber is normally closed by the conduit opening/closing mechanism (26), and the other end passes through the machine room (20) from the drain port (27) formed in the bottom wall of the insulation box (2), and is inserted through the bottom wall of the machine room (24). It is connected to a drainage vibrator (28).

An electric compressor (29), a condenser (30), and a condenser cooling fan (31), which together with the evaporator (11) constitute a refrigeration system, are installed in the machine room (24).

Next, the operation of the thawing warehouse will be explained. This driving is 4
It consists of different operation modes, each mode is thawing operation, tightening operation, cold storage operation and washing operation. By pressing the thawing button, washing operation - thawing operation - washing operation - tightening operation → cold storage operation are automatically selected. Do this in sequence.

First, in the cleaning operation, the water supply solenoid valve (21) opens and the water supply pipe (
18) to the water storage tank (17), and when a predetermined amount of water is supplied, the water level detection device (20) detects this and closes the water supply electromagnetic valve (21) to stop the water supply. At the same time, the pump device (22) operates, and the water in the water storage tank (17) is pumped through the feed pipe (
23) to the sprinkler (13) and from the injection nozzle (13A) to the air inlet face (IIA) of the evaporator (11).
Water is sprinkled towards. This water falls into a water collector (16) placed below the evaporator (11), passes through a return pipe (19), and is collected into a water storage tank (17). When the predetermined watering time has elapsed, the pump device (22) stops to end the watering operation, and at the same time, the drain pipe (25) is opened by the pipe opening/closing mechanism (26), and the water in the water storage tank (17) is released. The water passes through the drain pipe (25) and is completely drained from the drain vibrator (28).

This drainage operation is temporally controlled, and after a predetermined period of time, the drain pipe (25) closes and the drainage operation ends.

In the subsequent thawing operation, the water supply solenoid valve (2
1> opens to supply water from the water supply pipe (18) to the water storage tank (17), and when a predetermined amount of water is supplied, the water supply solenoid valve (21) closes to stop the water supply. At the same time, the pump device (22) operates, and the water in the water storage tank (17) is forced to the water sprinkler (13) through the feed pipe (23), and from the injection nozzle (13A) to the air inlet surface of the evaporator (11). Water is sprinkled towards (IIA). On the other hand, the operation of the refrigeration system, which starts operation based on the completion of the cleaning operation, is controlled so that the temperature inside the refrigerator is maintained at, for example, 5°C, and the operation is controlled so that the temperature inside the refrigerator is maintained at 5°C,
0) is to quickly raise the internal temperature, which drops due to the influence of frozen food at the beginning of thawing operation, to the set temperature.
Turns on/off at a temperature slightly lower than the temperature set inside the refrigerator.
do. Therefore, the cold air heat-exchanged in the evaporator (11) is
The evaporator (11) contains fine particles of water sprinkled on it and becomes humid. The constant-temperature, high-humidity cold air that passes through the evaporator (11) in a high-speed airflow due to the operation of the iL machine (14) is circulated to the storage section (3) as indicated by the white arrow (A> in Fig. 1).
Thaw the frozen food (32).

By the way, the water sprinkled on the evaporator (11) during the thawing operation is not entirely contained in the cold air and circulated, but falls from the evaporator (11) to the water collector (16) as surplus water. Furthermore, the water that has bounced back from the evaporator (11) is prevented from further scattering backward by the eliminator (12).
The water falling from the eliminator (12) is collected in the water collector (16).
Furthermore, water falling from the blower (14) is also collected in the water collector (16). Like this water collector (16)
The water that has fallen into the tank passes through the return pipe (19) to the water storage tank (
17) and reused. Although the thawing time varies depending on the type and amount of frozen food (32), the freezing device, blower (14) and pump device (22) are stopped for a preset time based on empirical data. , At the same time, open the drain pipe (25) and open the water storage tank (17).
Drain all the water and end the thawing operation.

When the thawing operation is completed, the cleaning operation is started again. This cleaning operation is carried out in exactly the same way as the above-mentioned cleaning operation that was carried out prior to the thawing operation, and the water storage tank (17
) is pumped by a pump device (22) through a feed pipe (23) to a sprinkler (13), and from an injection nozzle (13A) of the sprinkler (13) to an evaporator (11).
), and the water falling from the evaporator (11) is transferred to the return pipe (
After a predetermined period of water circulation to be collected through water tank (19) and water tank (17), all the water in water tank (17) is drained. This prevents drips and oil generated during thawing operation and remaining in water circulation circuits such as the evaporator (11), water sprinkler (13), return pipe (19), pump device (22), and feed pipe (23). and keep these water circulation circuit components clean.

When such a cleaning operation is completed, a tightening operation is subsequently started. This tightening operation is performed by controlling the operation of the refrigeration equipment so that the temperature inside the refrigerator is maintained at -3°C, which is slightly lower than 0°C, and by operating the blower (14), ice is formed on the surface of the food (32). This is done to form a film to reduce the outflow of drips and to eliminate temperature non-uniformity between the surface temperature and center temperature of the thawed food (32). In other words, a thawing operation performed at a temperature above 0°C forms an ice film on the surface of food that has been completely thawed, thereby preventing a large amount of drips from flowing out. If there is, the center will thaw due to heat transfer from the thawing part that is at a temperature of 0°C or higher, and the surface temperature and center temperature will gradually balance out. This tightening operation also waits for a preset time, but in this case, care must be taken to prevent the ice film from growing excessively and eventually refreezing the thawed food. This is cold storage operation.

In other words, the cold storage operation that follows the tightening operation is at 0°.
The internal temperature set by the above tightening operation is slightly lower than C (-3
The operation of the refrigeration system is controlled so that the temperature inside the refrigerator is maintained at a temperature slightly higher than the temperature (for example, -1°C), and the rotational speed of the blower (14) is reduced to prevent food from drying out to circulate cold air. This is done at a slower speed. This prevents the thawed food from refreezing and continues to suppress the outflow of drips. As a result, the thawed food is preserved at high freshness for a long period of time until it can be put into cooking bags as needed.

By the way, the temperature set inside the refrigerator in the tightening operation mentioned above is such that the temperature (freezing point) at which the load of meat and fish, which are often handled as frozen foods, freezes is approximately -1.7°C for meat and approximately -1.7°C for fish. Since the temperature is 1.3℃, the temperature is set slightly lower than these freezing points, and the set temperature in the refrigerator during cold storage operation is lower than 0℃ and slightly higher than the freezing point, which is the so-called freezing temperature. As a result, the tightening operation prevents a large amount of drips from flowing out, and the cold storage operation maintains the high freshness of the food.

In the above embodiment of the present invention, the cleaning operation is performed between the thawing operation and the tightening operation, but it does not depart from the gist of the present invention even if the tightening operation is performed following the thawing operation. .

(g) Effects of the Invention As described above, the present invention can prevent drips from flowing out of the food by forming an ice film on the surface of the food through the tightening operation performed after the thawing operation of the frozen food. This has the excellent advantage of suppressing deterioration in taste and weight loss, maintaining good quality, and achieving uniform thawing of frozen foods.

In addition, after the tightening operation, the cold storage operation, which is performed at a temperature below 0°C and slightly higher than the freezing point of the food, suppresses the excessive growth of the ice film formed during the tightening operation, and refreezes the thawed food. This has the remarkable advantage that it can prevent the leakage of drips, and can preserve thawed foods with high freshness for a long period of time.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view of a thawing warehouse implementing the present invention, Fig. 2 is a front view thereof, Fig. 3 is a sectional view taken along line A-A in Fig. 2, and Fig. 4
The figure is a cross-sectional view taken along the line BB in FIG. 2, and FIG. 5 is a diagram showing the operating state of the equipment provided in the thawing warehouse of the present invention in each operating mode and the internal temperature change in each operating mode. (3)...storage section, (11)...evaporator, (1
3)... Water sprinkler, (14)... Air blower, (17
)...water storage tank, (22)...pump device,
(32) Frozen food.

Claims (1)

[Claims] 1. Thaw the frozen food using humid cold air at a temperature higher than 0°C, then tighten the food to form an ice film on the surface of the food using cold air slightly lower than the freezing point of the food, and then thaw the food at a temperature lower than 0°C. A method for thawing and preserving food, characterized in that the food is kept cold by cold air at a temperature slightly higher than the freezing point of the food.