JPS6236171A - Retention of freshness of perishable food - Google Patents

Abstract

PURPOSE:To prevent the wilting and deterioration of a perishable food and retain the freshness thereof, by housing a frozen material of a hydrated highly absorbing polymer together with the perishable food in a container, reducing the material temperature of the perishable food and keeping the humidity at an optimum value. CONSTITUTION:Water in an amount of preferably 50-500 times based on a highly water absorbing polymer, preferably a highly water absorbing polymer, e.g. post-crosslinked polyacrylic acid salt, etc., contained in a sheetlike structure, e.g. paper, is absorbed therein and frozen preferably at <=-10 deg.C to give a frozen material, which is, together with a peroishable food, e.g. vegetable, is housed in a container to keep the freshness thereof.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for preserving the freshness of fresh foods, and more specifically, the present invention relates to a method for preserving the freshness of fresh foods such as fish and vegetables. 0 [Prior art and its problems] As a method for preventing freshness of fresh foods from decreasing, One method is to lower the temperature of fresh foods by placing bare ice or ice wrapped in plastic film in a container. For this reason, refrigerators and refrigerated trucks are used, but sometimes there are not enough refrigerators or refrigerated trucks, or even if a refrigerator or refrigerated truck can be used, it is not possible to lower the temperature of individual perishable foods sufficiently. In some cases, as the temperature inside the container rises, the ice melts and becomes liquid.

Melt 1 cup of this liquid in water.

``There was a problem that the quality of fresh foods deteriorated due to the formation of ridges.In addition, even if the temperature of the food was lowered sufficiently, the low humidity inevitably caused a decrease in the freshness of fresh foods, such as 'wilting'. .

[Means for solving problems]

Therefore, in order to solve the above-mentioned drawbacks, the present inventors conducted intensive research to obtain a cold insulating material that has sufficient cooling capacity and can maintain optimal humidity. It was discovered that the temperature of perishable foods can be lowered by absorbing water containing water, which is then frozen and used as a cold insulator, and can also prevent the fresh foods from wilting and deteriorating. The completed 0, that is, the present invention,
The present invention provides a method for preserving the freshness of perishable foods, which is characterized in that a frozen superabsorbent polymer hydrated is placed in a container together with fresh foods and cooled.

The superabsorbent polymer according to the present invention is a substance that is insoluble in water, absorbs a large amount of water when it comes into contact with water, and has a water absorption capacity of 30 times or more than its own weight. Starch-polyacrylonitrile graft copolymer disclosed in Japanese Patent Publication No. 51-39672
Cross-linked polyalkylene oxide disclosed in Japanese Patent Publication No. 53-13495, saponified vinyl ester-ethylenically unsaturated carboxylic acid copolymer disclosed in Japanese Patent Publication No. 13495/1986,
Self-crosslinking polyacrylate obtained by the reverse phase suspension polymerization method disclosed in JP-A No. 4-30710, JP-A-54-2
No. 0095 discloses a reaction product of a polyvinyl alcohol polymer and a cyclic acid anhydride, JP-A-55-843
Examples include the polyacrylate crosslinked product disclosed in JP-A-59-62665 and the post-crosslinked polymer disclosed in JP-A-59-62665. A particularly preferred superabsorbent polymer is a substance having a water absorption capacity of 100 times or more its own weight, such as post-crosslinked polyacrylate. The shape of the superabsorbent polymer used in the present invention is not particularly limited, and may be in the form of powder, granules, granules, blocks, scales, sheets, etc. However, due to handling and other reasons, paper , those contained (or sandwiched) in sheet-like structures such as nonwoven fabrics are preferred.

The amount of water absorbed by the super absorbent polymer is usually 50 to 500 times (by weight) the amount of water absorbed by the super absorbent polymer. In the case of absorbing an aqueous solution of an inorganic salt, examples of the inorganic salt include common salt, mirabilite, and soybean salt. The concentration of aqueous solution is usually 0.01
~10% by weight.

The frozen super absorbent polymer is prepared by freezing the water-absorbed polymer at -5°C or lower, preferably -10°C.
Obtained by freezing: .

The amount of frozen food to be used is arbitrarily selected depending on the type of fresh food, storage period, etc., but it is usually 0.1 for vegetables.
~3.04 (1 to 4 for vegetables), 0°1 for fresh fish
~a, a q (1- for fresh fish) is used.

Examples of fresh foods whose freshness can be maintained by the method of the present invention include broccoli, mushrooms, mushrooms, watercress, etc.
Spinach, lettuce, cauliflower, celery, asparagus, Chinese chrysanthemum, chive, butterbur, strawberry, etc. Fungi include matsutake, enoki mushroom, shiitake, etc. Fresh fish include sea bream, yellowtail, yellowtail, bonito, red clam, shrimp, crab, etc. can be mentioned.

[Action and effect]

By using the frozen superabsorbent polymer that has absorbed water according to the present invention, it is possible to maintain a low temperature for a long time with the same amount of ice or ice packs currently available on the market. This is because water is absorbed by the water-absorbing polymer, which is a high electrolyte, and when it is frozen, a large amount of heat is required to melt it. If an aqueous solution of inorganic salt is used, it can be maintained for a longer period of time and a sterilizing effect can also be expected.

Furthermore, according to K, the reason why fresh foods can be prevented from wilting and deteriorating is because the humidity in the air can be controlled as frozen materials melt.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples.0 Example 1 A styrene foam container with an inner diameter of 33.501×2401×11.51)I (height) was cooled in advance to 10°C. Absorb water (water absorption is 300 F) into a water-absorbing polymer sheet (containing 40 t/m2 polymer, 30 os vertically x 22 os horizontally), then cool it at -20°C and freeze it in the above container. The container was transferred to a constant temperature room at 45% relative humidity and the temperature and humidity inside the container were checked over time. Also, for comparison, ice SOOF, commercially available ice packs (soar/unit)
Similar to the water-absorbing polymer sheet, 2 pieces were kept at -20℃ and placed in the above Styrofoam container, and the temperature and humidity inside the container were similarly checked.The results are shown in Figures 1 and 2. show.

In the same figure, &1 is Styrofoam only, and Ya2 is ice 300.
F and M3 are commercially available ice packs, and &4 is the result for a water-absorbing polymer-containing sheet that has absorbed 500 tons of water and frozen.

From the results shown in Figures 1 and 2, it is clear that when a water-absorbing polymer sheet is used, the temperature inside the container is maintained at a low temperature for a long period of time, and that the relative humidity causes "condensation" and "wilting" of fresh foods. “It is clear that the temperature is maintained at approximately 70% where no deterioration occurs.

Example 2 Based on the basic experiment of Example 1, a similar experiment was conducted using broccoli, which has a very high respiration rate among fresh foods.

Three broccoli noodles were placed in the same styrofoam as used in Example 1, and after pre-cooling to 10°C, the temperature was 25°C and a relative humidity of 4.
Placed in a 5% constant temperature room, temperature and humidity changes inside the container, and 18
The freshness state after hr was observed. The results are shown in Table 1.

Example 3 Based on the basic experiment of Example 10, a similar experiment was conducted using enoki mushrooms whose quality deteriorates significantly.

Enoki mushrooms 3 to 3 were placed in the same styrofoam as used in Example 1, and after pre-cooling to 10°C, the temperature was 25°C and the relative humidity was 45°C.
% temperature and humidity change and 24 hours.
The amount of enoki mushrooms left behind was expressed as a weight reduction rate (%). The results are shown in Table 2.

Example 4 Based on the basic experiment of Example 10, a similar experiment was conducted using Thai sashimi, which suffers from severe quality deterioration.

Put 2q of Thai sashimi into the same styrofoam used in Example 1, pre-cool to 10°C, and then heat to 25°C and relative humidity 45%.
The Thai sashimi was placed in a constant temperature room and the temperature and humidity changes within the container were observed, as well as the freshness of the Thai sashimi after 24 hours. The results are shown in Table 3.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the temperature change over time in the container in the basic experiment conducted in Example 1, and FIG. 2 is a diagram showing the humidity change over time.

Claims (1)

[Scope of Claims] 1. A method for maintaining the freshness of fresh foods, which comprises placing a frozen superabsorbent polymer hydrated with fresh foods in a container and cooling them. 2. The method for preserving the freshness of perishable foods according to claim 1, wherein the superabsorbent polymer is contained in a sheet-like structure.