JPH09252755A - Freezing, storing and defrosting of food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the long storage of a boiled rice food obtained by combining boiled rice with other foods holding the quality as it is prepared or having higher quality. SOLUTION: This method comprises processes of freezing, storing and defrosting of a food. A boiled rice food, obtained by combining boiled rice with one or more other foods, is frozen by blowing liquefied carbonate gas until the temperature at the center reaches in the range of -15 to -30 deg.C, the frozen food is stored at <=-25 deg.C, and subsequently the food is defrosted at about 40-60 deg.C for at least a part of the defrosting period.

Description

Detailed Description of the Invention

[Background of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for freezing, preserving, and thawing foods that combines cooked rice and one or more other foods, the quality of which does not change even after long-term storage.

[0002]

2. Description of the Related Art The number of sales of bento, which is a food that is a combination of cooked rice and other foods, is severely fluctuated day by day, and since it cannot be stored, it must be manufactured on the day of manufacture. That prediction has become a major issue.
In addition, the manufacturing time is often early in the morning, which is a heavy burden. Therefore, there has been a long-awaited demand for a technique in which an averagely manufactured product is frozen and stored once in the daytime and thawed as much as necessary. Regarding a single processed food, although it has been solved almost technically as you can see from the fact that many frozen foods are sold, frozen foods that combine cooked rice and other foods by a known method are stored. Nothing was satisfactory in terms of quality even after thawing.

[Summary of the Invention]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for long-term storage of cooked rice food, which is a combination of cooked rice and other foods, with the quality as prepared or higher. To do.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the inventors of the present invention freezed the target food by spraying liquefied carbon dioxide until the central temperature reaches −15 to −30 ° C. Then, it was found that the above problems can be solved by performing cryopreservation in an atmosphere of -25 ° C or lower and then thawing in an atmosphere of about 40 to 60 ° C for at least a part of the total thawing time. It came to completion. That is, the present invention comprises steps of freezing / preserving and thawing food, and a cooked rice food in which cooked rice and one or more kinds of other foods are combined is sprayed with liquefied carbon dioxide gas so that the central temperature of the cooked rice food is -15 to- After freezing to 30 ° C. and cryopreservation under an atmosphere of -25 ° C. or lower, about 40 ° C. to 60 ° C. for at least part of the thawing time.
A method for freezing, preserving and thawing foods, characterized by thawing in an atmosphere of ° C. A preferred embodiment of the thawing step in the present invention is a method for freezing / preserving and thawing foods, wherein thawing at about 40 to 60 ° C. is performed at a stage where the central temperature of cooked rice passes the melting temperature of ice crystals. . One preferable mode of the present invention is to freeze pressed sushi until the center temperature of cooked rice reaches -15 to -30 ° C by spraying liquefied carbon dioxide, and then to -25 to -25.
After cryopreservation in an atmosphere of -35 ° C, it is thawed rapidly in an atmosphere of about 40 ° C for a period of center temperature of about -5 ° C, and thawed in an atmosphere of 14 to 25 ° C for other thawing times. It is a method for freezing / preserving and thawing foods characterized by the following. Another preferable embodiment of the present invention is that a bento box prepared with side dishes and cooked rice is frozen until the central temperature of cooked rice reaches −15 to −30 ° C. by spraying liquefied carbon dioxide, and then −25 to − It is a method of freezing / preserving and thawing a food, which comprises performing cryopreservation in an atmosphere of 35 ° C and then thawing in an atmosphere of about 40-60 ° C.

DETAILED DESCRIPTION OF THE INVENTION The method of freezing / preserving and thawing food according to the present invention is a cooked rice food in which cooked rice and one or more kinds of other foods are combined, and the central temperature is −15 to −15 by spraying liquefied carbon dioxide gas. After freezing to −30 ° C. and cryopreservation in an atmosphere of −25 ° C. or lower, about 40 ° C. to 60 ° C. for at least part of the thawing time.
What is characterized in that it is thawed in the atmosphere of ° C. is as described above, by combining a freezing step of a specific condition, a storage step and a thawing step, a cooked rice food that combines cooked rice and other foods, It allows long-term storage with the quality as prepared or higher.

The food subject to the present invention is a cooked rice food which is a combination of cooked rice and one or more kinds of other foods. As a preferred specific example, seafood such as mackerel, horse mackerel, crab and the like is used as vinegared rice. Typical examples include pressed sushi placed on top and pressure-molded, and Makunouchi bento, which is a combination of cooked rice, fried egg, fried food, tempura, and other cooked rice with cooked rice.
However, there is no particular limitation, and it goes without saying that it can be widely applied as long as it is a combination of cooked rice and one or more kinds of other foods such as rolled sushi and rice balls with ingredients.

In the present invention, the above-mentioned cooked rice food is first subjected to a freezing step by directly spraying liquefied carbon dioxide gas. At this time, it is desirable that the food is not packaged so that the liquefied carbon dioxide gas is directly sprayed. However, if it is difficult to unwrap such as pressed sushi, you can wrap it with a thin transparent film for food, and if it is a kind of Makunouchi bento, put the food in a box and leave it without the top lid. A method such as freezing may be used. Frozen food has a core temperature of -15, which is the most difficult to cool (usually rice).
Continue until ~ 30 ° C range. Even if the temperature exceeds the predetermined range or the temperature is less than the predetermined range, the quality after thawing is deteriorated, which is not preferable. If the storage period is about half a year, the food can be stored almost as it was prepared without deterioration in quality. In the case of a small scale, this freezing process may be performed by using a normal liquefied carbon dioxide gas spraying device, and at a large scale, it may be performed by using a tunnel type liquefied carbon dioxide gas spraying device.

After reaching the above-mentioned predetermined freezing temperature condition, the cooked rice food is transferred to a storage step and stored for a necessary period until it is subjected to the next thawing step. Storage is performed at -25 ° C or lower, preferably in the range of -25 to -35 ° C. In this storage step, if the temperature exceeds the predetermined temperature range, the quality after thawing is deteriorated, which is not preferable. In addition, this preservation process can be performed using a normal food freezer.

The frozen cooked rice food is transferred to the final thawing step. The thawing step is about 40 ° C to 60 ° C (specifically 38 ° C) for at least a portion of the total thawing time.
Thaw treatment performed under an atmosphere of up to 62 ° C. That is, thawing under this specific temperature range condition is essential in the thawing step, and other thawing temperature conditions may be used in combination as necessary. Specifically, it is not necessary to perform all the steps of thawing within the above specific temperature range, and at a specific stage,
Preferably, when the central temperature of the food that is the most difficult to warm passes through the melting temperature of ice crystals (generally around -5 ° C), it is about 40
Although it is essential to perform thawing within the melting time range of ice crystals (rapid thawing process) under the temperature condition of 60 ° C to 60 ° C,
At other times, if necessary, the lower limit of approximately 40 ° C
This means that the thawing may be performed gently at a temperature lower than (specifically 38 ° C.). Therefore, in the thawing step of the present invention, depending on the type or nature of the food, a combination of rapid thawing under the specific temperature condition and slow thawing under a lower temperature condition is preferred, and only when the thawing process is performed only rapidly. It may be able to be efficiently thawed. For example, at the melting temperature of ice crystals (around -5 ° C), there is almost no change in the product temperature, but there is almost no change in the product temperature. Therefore, in the case of cooked rice foods that use fresh fish, such as pressed sushi, In order to maintain the quality of raw fish, it rapidly thaws at about 40 ° C (specifically 38 to 42 ° C) when the center temperature is around -5 ° C.
When the central temperature is other than that, it is desirable to slowly thaw at 14 to 25 ° C, more preferably about 20 ° C (specifically 18 to 22 ° C). The rapid thawing time is a time within the melting time of ice crystals, and this time is, for example, about 20 to 60 minutes, although it varies depending on the amount of cooked rice food and the like. In addition, for cooked rice foods such as Makunouchi bento that do not use raw fish, it takes about 40
Rapid thawing is possible only under the temperature condition of -60 ° C. In addition, in the thawing step, a normal thermostat capable of setting a constant temperature can be used. It is included.

The foods finally thawed by the above-mentioned method of the present invention after being frozen and stored, as shown in the Examples below, maintain the quality of all foods including cooked rice at the time of preparation. I found out that Further, regarding the pressed sushi, the panelists obtained that the taste was improved by freezing and thawing by the method of the present invention as compared with the freshly prepared one.

[0011]

The following examples further illustrate the present invention. [Example 1] Pressed mackerel sushi (a rectangle having a long side of 5 cm and a short side of 3 cm and a length of 25 cm) produced by a usual method is frozen by spraying liquefied carbon dioxide while being wrapped with a transparent film for food. did. Figure 1 shows the temperature change in the center of sushi rice at that time.
It was shown to. After that, it was wrapped with bamboo skin, wrapped with a pillow wrapping machine, transferred to a freezer at -30 ° C, and stored as it was. 1
After a week, it was taken out from the freezer and heated in a constant temperature oven with an internal temperature of 20 ° C. for 180 minutes until the central temperature reached about −5 ° C., and then heated at an internal temperature of 40 ° C. for 40 minutes. Then again 2
It was thawed by heating at 0 ° C. The temperature change at that time is shown in FIG.

[Comparative Example 1-1] The same procedure as in Example 1 was carried out except that the freezing method was carried out by placing in an air-blast type freezer at -60 ° C instead of spraying the liquefied carbon dioxide gas. In this case, the internal temperature was almost the same as when the liquefied carbon dioxide was blown, but the freezing time was long.

[Comparative Example 1-2] The same procedure as in Example 1 was carried out except that, instead of spraying the liquefied carbon dioxide gas, the freezing method was carried out in an air blast type freezer at -25 ° C. In this case, the freezing time was longer than 1-1.

[Comparative Example 1-3] The defrosting method was changed to 40 ° C. for 40 minutes at the internal temperature of 65 ° C. when the central temperature was about −5 ° C.
Performed in the same manner as in Example 1.

[Comparative Example 1-4] The storage method was as follows:
Example 1 was repeated except that a freezer at -5 ° C was used.

[Comparative Example 1-5] The storage method was as follows:
The same procedure as in Example 1 was performed except that a freezer at about 20 ° C. was used.

Evaluation Example 1 Example 1 and Comparative Examples 1-1 to 1-1
The taste of 5 mackerel pressed sushi products and those not frozen were evaluated by 7 trained panelists. As a result, in the case of Example 1, 5 people answered that the taste was good compared with the case in which it was not frozen.
Although there were no differences in the names, 6 people in Comparative Example 1-1 and 7 people in 1-2 all recognized drip from the mackerel, and particularly 1-2, the aging of sushi rice was observed. All pointed out. Regarding Comparative Example 1-3, the five panelists pointed out the discoloration of the mackerel and answered that the taste was impaired. In addition, four people also obtained the answer that the taste of Example 1 was mellow. Regarding Comparative Examples 1-4, all pointed out that the sushi rice was hard and aged, and
In both -4 and 1-5, the vinegar taste of sushi rice was weakened, and the answer was that the taste was changed.

[Example 2] Makunouchi bento (17 cm in length x 25 cm in width x 3.5 cm in thickness) manufactured by a conventional method was packed in a box and then frozen by spraying liquefied carbon dioxide gas without the upper lid. . The temperature change of the central portion of the white rice at that time is shown in FIG. After that, the transparent film was covered with an upper lid so as to cover the upper surface of the bento box, transferred to a freezer at -30 ° C, and stored as it was.
One week later, it was taken out of the freezer and heated in a constant temperature oven having an internal temperature of 60 ° C. for 100 minutes. FIG. 4 shows the temperature change in the central portion of the white rice at that time. This Makunouchi bento is white rice and grilled mackerel,
Fried chicken, egg fried, kamaboko, shrimp tempura, university potato,
It consists of side dishes such as marinade, cherry pickles, boiled beans, dried plums, canned pineapple or cherry.

[Evaluation Example 2] With respect to Example 2 and Makunouchi bento that were not frozen and preserved, the taste was evaluated by seven trained panelists. As a result, in the case of Example 2, 3 persons answered that the taste was good and 4 persons answered that there was no difference, as compared with the case where it was not frozen and preserved. According to the panelists' individual responses, there is no difference in the texture of grilled mackerel / fried chicken without the texture of the meat being frozen and preserved. Things have been obtained.
In addition, tempura was preserved with its clothes in a plain state.

[0020]

As described above, according to the method of the present invention, by combining the freezing step, the preserving step and the thawing step under specific conditions, the cooked rice food in which cooked rice and other foods are combined can be prepared at the time of adjustment. It can be stored for a long period of time with the quality of or higher.

[Brief description of drawings]

FIG. 1 is a graph showing a temperature change in a central portion of sushi rice by freezing treatment of mackerel pressed sushi (Example 1).

FIG. 2 is a graph showing the temperature change of the central part of sushi rice due to the thawing process in Example 1.

FIG. 3 is a graph showing a temperature change in the central portion of the white rice due to the freezing process of the Makunouchi bento (Example 2).

FIG. 4 is a graph showing a temperature change of a central portion of rice cooked by thawing in Example 2.

Front page continued (72) Inventor Shigeki Uchida 8-27 Yayoi-cho, Yonago-shi, Tottori Prefecture Yonego Co., Ltd. (72) Inventor Takaaki Nakamura 1-1-25 Shinurashima-cho, Kanagawa-ku, Yokohama-shi Kanagawa Engineering Co., Ltd. (72) Inventor Seiji Kasuya 1-1-25 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Kirin Engineering Co., Ltd. (72) Inventor Mikiyuki Kano 1-1-25 Shin-urashima-cho, Kanagawa-ku, Yokohama, Japan Kirin Engineering Co., Ltd. Within

Claims (4)

[Claims] 1. A process of freezing, preserving and thawing foods, wherein a cooked rice food, which is a combination of cooked rice and one or more other foods, has a central temperature of -1 by spraying liquefied carbon dioxide gas.
It is characterized in that it is frozen to 5 to -30 ° C, frozen and stored in an atmosphere of -25 ° C or less, and then thawed in an atmosphere of about 40 ° C to 60 ° C for at least a part of the thawing time. How to freeze, store and thaw food. 2. The method for freezing / preserving and thawing food according to claim 1, wherein the thawing at about 40 to 60 ° C. is performed at the stage where the central temperature of cooked rice passes the melting temperature of ice crystals. 3. Pressed sushi is frozen to a center temperature of −15 to −30 ° C. by spraying liquefied carbon dioxide and then frozen and stored in an atmosphere of −25 to −35 ° C. Rapid thawing in an atmosphere of about 40 ° C for a period of temperature of about -5 ° C, and 14 to 25 for other thawing times.
The method of freezing / preserving and thawing food according to claim 2, wherein the food is thawed in an atmosphere of ° C. 4. A bento box containing side dishes and cooked rice is sprayed with liquefied carbon dioxide so that the center temperature of cooked rice is -15 to-
3. Freezing and preserving the food according to claim 2, wherein the product is frozen to 30 ° C., frozen and stored in an atmosphere of −25 to −35 ° C., and then thawed in an atmosphere of approximately 40 to 60 ° C. How to defrost.