JPH1132670A - Freezing and thawing vegetable-based food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for freezing fresh, vegetable-based food without needing ventilation, moisture control or strict temperature control, and at a lower cost than CA storage so as to preserve their shapes, touch, tastes and color intact by spraying or sprinkling a refrigerant onto them in mist or shower. SOLUTION: This method freezes vegetable-based foods by spraying or sprinkling a refrigerant onto them in mist or shower. They may be immersed in a refrigerant to be frozen. They may be sprayed or sprinkled with a refrigerant in mist or shower and then immersed in a refrigerant to be frozen. The refrigerant may be at least one type of alcohol compounds selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, pentyl alcohol, ethylene glycol and glyceriol, or its mixture with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for freezing plant foods, a method for preserving frozen plant foods and a method for thawing the same, particularly a method for freezing fruits, fruits and vegetables, and a method for thawing frozen products. It is about. More specifically, the present invention relates to a method for freezing and thawing a plant-based food, which retains its shape, feel, taste, and color before being stored frozen.

[0002]

2. Description of the Related Art The long-term storage of foods makes it possible to provide the foods to the market regardless of the season, thereby enriching the eating habits. Fruits can be stored at room temperature,
There are low temperature storage, CA storage, ice temperature storage and the like. Room temperature storage
It is stored at the normal temperature of the place of production or accumulation, generally 10 ° C. or higher. Cold storage is a method of storing at a low temperature of 0 ° C to 10 ° C. CA storage is a method of storing at the same temperature as low-temperature storage by controlling the concentration of an atmosphere such as oxygen or carbon dioxide gas. Ice temperature storage is storage at a temperature below freezing such that it does not freeze.

[0003] Room temperature storage has the advantage that the temperature of the production area can be used as it is, and no special low-temperature equipment is required.
Management of ventilation, humidity, etc. is required, and the installation of an appropriately designed storage is required. At room temperature of 10 ° C. or more, the shelf life of the fruit is relatively short, and usually depends on the kind of the fruit, the place of storage, and the like, but is usually limited to two to three months.

[0004] In cold storage, storage is performed at a low temperature between 0 ° C and 10 ° C. Even in low-temperature storage, the storage of most fruits is limited to about 3 to 4 months. When stored at low temperatures in winter, the fruits freeze and consequently the fruits deteriorate. Even if it does not freeze, at temperatures near 0 ° C., the deterioration of the fruit may be accelerated. Therefore, in low-temperature storage, temperature control is required to keep the minimum temperature at least 2 ° C to 3 ° C or more.

[0005] In CA storage, the same temperature as in low-temperature storage may be used, but it is necessary to keep the oxygen concentration, carbon dioxide concentration and the like within a certain range, which requires a great deal of equipment. When the oxygen concentration or the carbon dioxide concentration is out of the control range, browning or burnt of the fruit occurs. Particularly in the case of mass storage, such problems may occur partially in the stored fruit.

[0006] In ice temperature storage, fruits must be stored so as not to freeze, and strict control of temperature is required. In particular, when storing a large amount of fruit, the temperature tends to be non-uniform, and in portions where the temperature is outside an appropriate value, the fruit undergoes deterioration such as freezing.

[0007]

As described above, the conventional method for storing fruits requires a short storage period (normal temperature storage,
Low temperature storage), ventilation and humidity control (normal temperature storage), strict temperature control (low temperature storage, CA
Many disadvantages such as storage and ice temperature storage, large equipment cost for controlling the concentration of atmosphere (CA storage), and alteration of stored materials due to fluctuation and unevenness of temperature and atmosphere (CA storage and ice temperature storage) There is. These storage problems are not limited to fruits, but are equally observed in the storage of fruits and vegetables and root vegetables. In addition, when stored frozen, the shape, taste, or color of a plant-based food is likely to change, including changes during the thawing process.

An object of the present invention is to eliminate the need for ventilation and humidity control, no strict temperature control, the same facility cost as low-temperature storage, cheaper than CA storage, and the fluctuation and unevenness of atmosphere. CA storage without fear of deterioration of storage
It can be stored for a long period of time equal to or higher than ice temperature storage, and also preserves the shape, feel, taste and color of fresh plant foods that are not frozen during the freezing storage and subsequent thawing process. An object of the present invention is to provide a method for freezing and thawing a vegetable-based fresh food such as fruits and vegetables.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention has been accomplished as a result of intensive studies focusing on frozen storage. The gist of the present invention is characterized in that a plant-based food is sprayed or sprayed with a refrigerant in a mist or shower form,
Method of freezing plant-based food, plant-based food, characterized by immersing in a refrigerant, the method of freezing plant-based food, plant-based food, after spraying or spraying the refrigerant in a mist or shower,
Further, a method for freezing a plant-based food, wherein the plant-based food is sprayed or sprayed with a refrigerant, immersed in a refrigerant, or immersed in a refrigerant after spraying or spraying the refrigerant, characterized by being immersed in a refrigerant. Complete the freezing of, further characterized by blowing off the refrigerant remaining in the gas after discharging the refrigerant or removing by air drying, a method of freezing plant-based food,
The refrigerant is characterized by being composed of at least one alcohol selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, pentyl alcohol, ethylene glycol and glycerin, or the alcohol and water, The method is characterized in that at least one selected from the group consisting of ascorbic acid, citric acid, succinic acid, malic acid, tartaric acid, fumaric acid and dithiothreitol is contained in the refrigerant in an amount of 10% by weight or less with respect to the method of freezing plant foods and the refrigerant. The method of freezing plant foods, the temperature of the refrigerant is -1 ° C
A method for freezing a plant-based food and a method for thawing a frozen plant-based food, wherein
A method for thawing frozen plant foods, comprising thawing in an aqueous saccharide solution having a concentration of 1 mol / l to 10 mol / l or an aqueous salt solution having a concentration of 0.01 mol / l to 10 mol / l. is there.

[0010] When plant foods, particularly fruits and fruits and vegetables, are frozen and stored, there are problems that the shape of the fruits and the like are lost when thawed, and the feel and taste cannot be reproduced. Also, when the freezing is rapidly performed, only the surface of the food freezes first, and the contents freeze later. As a result, when the contents freeze, there is a problem that the food itself ruptures and bursts.
In particular, in frozen storage of fruits, refrigerated storage cannot be put to practical use unless these problems are solved.

[0011] In the present invention, the plant-based food is frozen using a refrigerant. At this time, alcohols are used as a refrigerant. Specifically, it can be used as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, pentyl alcohol, ethylene glycol or glycerin, or a mixed solution thereof or a solution obtained by adding water thereto. In practice, ethyl alcohol is preferably used.
Not only the use of ethyl alcohol alone, but also a mixed solution of ethyl alcohol and another alcohol can be used. Also, alcohol may contain water.

Alcohol has the property of being easily dissolved in water, and is often used in a form containing water. In the case of ethyl alcohol, etc., in simple distillation,
Creates an azeotrope and necessarily contains water. Hereinafter, a description will be given mainly of a case where ethyl alcohol is used as the refrigerant,
It is not limited to this.

[0013] It is necessary to freeze in such a way as to retain the original taste when thawed, and at the same time to thaw so as to retain the original taste. First, the freezing method will be described. A method of immersing the fruit as it is in a cooling medium such as liquid nitrogen and freezing it is known as an effective method, but when frozen by this method, the epidermis of the fruit freezes rapidly, and as described above, During the process the fruit itself bursts. On the other hand, when ethyl alcohol is used as the refrigerant, the ethyl alcohol penetrates into the skin of the fruit, causing a so-called freezing point lowering effect, and the freezing temperature of the skin decreases. As a result, the whole fruit can be efficiently cooled, and the whole fruit can be frozen without causing the fruit to burst. Furthermore, by immersing in ethyl alcohol or spraying or spraying with ethyl alcohol, the epidermis of the fruit is fixed and the epidermis becomes structurally harder, which makes it more resistant to rupture, which is more convenient for freezing the fruit. Become something.

In order to cause the freezing point to fall, it is sufficient that the refrigerant contains ethyl alcohol. In principle, the higher the concentration of ethyl alcohol in the refrigerant, the higher the effect is obtained. However, when ethyl alcohol is used as a refrigerant for freezing, it is naturally collected and reused.
From such an economic viewpoint, the concentration of ethyl alcohol in the refrigerant is determined. In consideration of the recovery of the ethyl alcohol used, since 95% by volume of ethyl alcohol is obtained in the simple distillation when water is contained, it can be used as it is.

The time for immersing the fruit in the refrigerant may be any time required for freezing the fruit to the core. Usually, on the assumption that fruits at a temperature of 2 ° C. to 4 ° C. are used, the immersion time is determined in consideration of the temperature of the refrigerant to be used. This time is between 10 and 90 minutes. In addition, the temperature of the refrigerant must be a temperature necessary for securely freezing the fruit, and is in a temperature range of -1 ° C to -50 ° C, preferably -5 ° C to
A temperature range of −20 ° C. is employed.

The effect of using ethyl alcohol as the refrigerant is not only to lower the freezing temperature of the fruit skin, but also to have a bactericidal effect based on the bactericidal action of ethyl alcohol and a hardening effect of the skin. Due to the bactericidal effect, there is no need to worry about bacterial contamination problems during storage as well as after thawing, and the food can be served with confidence. Since the fruit epidermis contains protein, the protein is fixed by ethyl alcohol and the epidermis becomes slightly hard. For this reason,
The contents of the fruit can be protected from the outside world. Of course, it also works to prevent the fruit from bursting during the cooling process.

Since ethyl alcohol is a flammable liquid, strict attention must be paid to its handling, ie, explosion and fire. Ethyl alcohol can also cause health problems, namely liver damage. From these viewpoints, after freezing the plant-based food by immersion in a refrigerant or the like,
It is preferred that the refrigerant adhering to the plant-based food be blown off with a gas or air-dried to remove ethyl alcohol. The removal or air-drying of the refrigerant must be performed in a state where the plant-based food is frozen, and is preferably performed at least when the temperature of the plant-based food is −5 ° C. or lower. In addition, it is preferable to cool the gas when air-dried, but it is necessary to take care that at least the temperature of the plant-based food does not rise to cause thawing. As the gas for spraying or air-drying, air is usually used, but nitrogen, carbon dioxide, argon and the like can be used if necessary.

In order to cool the plant-based food, there is a method of immersing in a refrigerant, and in addition, there is a method of spraying or spraying the refrigerant. The method of spraying or spraying is advantageous when treating a large amount of plant-based food at once. You may use together the method of spraying and spraying, and the method of immersion. In particular, a method of cooling at the beginning of cooling by spraying or spraying and then cooling by dipping is preferred. That is, first, the epidermis of the plant-based food is appropriately hardened and the freezing temperature is lowered by spraying or spraying the refrigerant, and then the whole fruit can be efficiently cooled by immersing in the refrigerant. When spraying or spraying a refrigerant containing ethyl alcohol, the spraying or spraying is performed in the form of a mist or a shower.

Ascorbic acid, citric acid,
At least one selected from the group consisting of succinic acid, malic acid, tartaric acid, fumaric acid and dithiothreitol
It is preferable that the content is 0% by weight or less. When thawing a frozen fruit or the like, the color of the fruit may change slightly. In the case of Kyoho, it shows a slightly reddish hue. By adding ascorbic acid to the refrigerant in an amount of 10% by weight or less, preferably 0.05% by weight to 1% by weight, it is possible to prevent a change in the color of the fruit, and to obtain a fruit almost inferior to fresh fruit. Can be.

Next, a decompression method will be described. Thawing is performed in a short time within 30 minutes by immersing in an aqueous solution of a saccharide having a concentration of 0.01 mol / l to 10 mol / l or in a salt aqueous solution having a concentration of 0.01 mol / l to 10 mol / l. Is preferred. By this thawing method, it is possible to avoid deterioration of foods during thawing, especially softening of fruits and the like and change in taste. As the saccharide, either a monosaccharide or a polysaccharide may be used, and a sugar alcohol may be used. For example, sucrose, fructose, glucose and mannitol can be used. Among them, sucrose is preferable because it can be obtained in a large amount and is inexpensive. For example, it is immersed in a 1% to 15% by weight aqueous sucrose solution at room temperature. Salts can be used instead of sugars.

When thawing frozen plant-based fresh food,
When thawed with water, water enters the fruit due to osmotic pressure and becomes a so-called blister state, which looks bad in appearance,
In addition, a decrease in taste is inevitable. In this regard, when thawing is performed in an aqueous solution containing salts or saccharides, it is possible to thaw without changing the contents of the plant-based food. Therefore, the shape of the plant-based food after thawing is not much different from that of the original fresh plant-based food, and the taste is not much different from that of the fresh plant-based food.

As described above, the refrigeration method of the present invention has been mainly described by taking grape as an example and mainly using ethyl alcohol as a refrigerant. However, the present invention is not limited to this.
In addition to grapes, it can be frozen,
Fruits such as citron, cherry, apricot, persimmon, tomato, cherry tomato, melon, cucumber, pepper, eggplant, eggplant, etc., burdock, taro, potato, sweet potato, lotus root,
It can be applied to plant-based foods such as root vegetables such as bamboo shoots. In particular, it is highly effective in preserving fruits in frozen foods.

As for the alcohol used as the refrigerant,
Ethyl alcohol is generally preferred, but not limited to. Alcohols other than ethyl alcohol can be used. Different types of alcohols may be mixed and used, or water may be mixed and used. The alcohol used is as described above.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to the following examples.

Example 1 Kyoho was taken in three chambers, and 95% by volume of isopropyl alcohol cooled to a temperature of about −20 ° C. was immersed for about 25 minutes while further cooling from the outside. The temperature of the alcohol rose to about −15 ° C. at the end of the immersion. This was divided into three groups and stored in a freezer at a temperature of about −20 ° C. for 1 month, 6 months and 12 months, respectively. After storage, each group has a temperature of about 2
Thawed in a 13% by weight aqueous solution of sucrose at 2 ° C for about 25 minutes. Each group did not differ from the fresh fruit in shape and taste. Fruit firmness was somewhat softer than fresh fruit.

[0025]

Example 2 Two peaks were taken and 95% by volume of ethyl alcohol cooled to a temperature of about -20 ° C was immersed for about 25 minutes while further cooling from the outside. The temperature of the ethyl alcohol rose to about -15C at the end of the immersion. This was divided into two groups and stored in a freezer at a temperature of about −20 ° C. for 2 months and 10 months, respectively. After storage, each group was thawed by placing it in a 12% by weight aqueous solution of sucrose at a temperature of about 20 ° C for about 25 minutes.
Each group did not differ from the fresh fruit in shape and taste. Fruit firmness was somewhat softer than fresh fruit.

[0026]

Example 3 As for grape types, about 2 g of steuben and red gloves were obtained while further cooling an 80% by volume aqueous solution of glycerin cooled to −20 ° C. from the outside.
Dipped for 0 minutes. The temperature of the aqueous glycerin solution rose to about -15C at the end of the immersion. This was stored in a freezer at a temperature of about -15 ° C for 6 months. After storage, the steuben and red glove were thawed by placing them in a 15% by weight aqueous solution of sucrose at a temperature of about 22 ° C for about 20 minutes. None of them differed in shape and taste from fresh fruit. Fruit firmness was somewhat softer than fresh fruit.

[0027]

Example 4 As a type of grape, steuben was immersed in ethyl alcohol cooled to -20 ° C. for about 20 minutes while further cooling from outside. The temperature of the ethyl alcohol rose to about -15C at the end of the immersion. This was stored in a freezer at a temperature of about -15 ° C for 6 months. After storage, steuben is sucrose 13% by weight at a temperature of about 20 ° C.
Thawed for about 20 minutes in aqueous solution. None of them differed in shape and taste from fresh fruit. Fruit firmness was somewhat softer than fresh fruit.

[0028]

Example 5 A stove and a red glove were individually taken, and a 75% by volume aqueous solution of ethylene glycol cooled to a temperature of about -20 ° C was sprayed using a nozzle. The solution was frozen by spraying a cooled aqueous solution of ethylene glycol to lower the temperature to -20 ° C. The time required for freezing was about 18 minutes.
By spraying the thus cooled ethylene glycol aqueous solution, it was possible to cool and freeze more effectively than the immersion treatment. After storing for 6 months in a frozen state, the frozen grape was thawed in the same manner as in Example 1 and the quality of the product was strictly compared with that of a fresh product. The result was obtained.

[0029]

Embodiment 6 A bunch of red gloves was taken and the temperature was about -18.
95% by volume of ethyl alcohol cooled to 0 ° C was sprayed into a mist using a nozzle. The cooled ethyl alcohol was sprayed to lower the temperature to -17 ° C and frozen. The time required for freezing was about 18 minutes. By spraying the thus cooled ethyl alcohol, it was possible to cool and freeze more effectively than the immersion treatment. After storing in a frozen state for 6 months, the frozen red glove was thawed in the same manner as in Example 1 and the quality of the product was strictly compared with that of a fresh product. Was obtained.

[0030]

Example 7 A kyoho was taken, and 99 volume% isopropyl alcohol cooled to a temperature of about -20 ° C was sprayed in a mist state for about 8 minutes, and finally the kyoho was immersed in the sprayed isopropyl alcohol. Cooling. During this period, Kyoho and the sprayed isopropyl alcohol were heated at -20 ° C.
Was forcibly cooled with an external refrigerant. The frozen Kyoho was obtained in about 15 minutes in total. The frozen Kyoho was stored frozen at -15 ° C for 4 months. After storage, 1% by weight instead of sucrose solution
Thawed using saline. In this case, as in Example 5, there was no difference from the fresh fruit in shape and taste. Fruit firmness was somewhat softer than fresh fruit.

[0031]

EXAMPLE 8 Sweet potatoes were placed in 95% by volume ethyl alcohol cooled to a temperature of about -20.degree.
Soak for minutes. The temperature of the ethyl alcohol at the end of the immersion was about -16 ° C. The frozen sweet potato was stored for 5 months in a freezer at a temperature of about −20 ° C. After storage, it was placed in a 10% by weight aqueous sucrose solution at a temperature of about 25 ° C. and thawed for about 30 minutes. The potatoes were placed in a home refrigerator for 24 hours, together with the potatoes, to equilibrate the temperature. The frozen sweet potatoes did not differ in taste and texture from fresh products.

[0032]

Example 9 A bunch of Kyoho was taken and cooled to -18 ° C.
It was immersed in a volume% of ethyl alcohol for 25 minutes and frozen.
Pull the frozen Kyoho out of the ethyl alcohol,
Air cooled to 0 ° C. was blown to blow off the remaining ethyl alcohol. At this time, instead of blowing off the refrigerant with a gas, the refrigerant may be air-dried. Due to the heat of vaporization of ethyl alcohol, Kyoho remained frozen. The frozen Kyoho was stored at −18 ° C. for 3 months. After storage, it was thawed using a 10% by weight aqueous sucrose solution. Good results were obtained as in Example 1.

[0033]

Example 10 Steuben and red gloves were immersed in 95% by volume isopropyl alcohol containing 0.1% by weight of ascorbic acid cooled to a temperature of about -20 ° C. for about 20 minutes. The temperature of the isopropyl alcohol rose to about -10C at the end of the immersion. This was stored in a freezer at a temperature of about -20 ° C for 6 months. After storage, each group is sucrose 10% by weight at a temperature of about 22 ° C.
Thawed for about 20 minutes in aqueous solution. The obtained fruit was not different from the fresh product in shape, taste and color. In the case of Steuben, the color after thawing retained the tone of the fresh fruit.

[0034]

According to the method for freezing and thawing plant-based foods of the present invention, fresh vegetable-based foods such as fruits, fruits and vegetables, root vegetables can be stored for a long period of 6 months or more, and even after a long storage. It has the feature that the original taste can be maintained almost completely. Further, in implementing the present invention, strict temperature control of the storage device is not required, and ventilation and humidity control are not required. When the refrigeration temperature is set to -10 ° C or lower, the accuracy of the temperature control is about ± 5 ° C, so that the equipment cost is not much different from low-temperature storage, and is much lower than CA storage. There is no risk of deterioration of the stored material due to changes in the atmosphere and uneven temperature in the storage, and the storage can be performed for a long time equal to or longer than the CA storage and ice temperature storage.

Claims (8)

[Claims] 1. A method for freezing a plant-based food, comprising spraying or spraying a refrigerant on the plant-based food in a mist or shower form. 2. A method for freezing a plant-based food, comprising immersing the plant-based food in a refrigerant. 3. A method for freezing a plant-based food, comprising spraying or spraying a refrigerant on the plant-based food in the form of a mist or a shower, and then immersing the refrigerant in the coolant. 4. A method for spraying or spraying a plant-based food with a refrigerant,
The refrigeration of the plant-based food is completed by immersion in a refrigerant, or immersion in a refrigerant after spraying or spraying the refrigerant, and further, the refrigerant is discharged and then the remaining refrigerant is blown off or removed by air drying. The method of freezing a plant-based food. 5. The method according to claim 1, wherein the refrigerant is methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol,
The plant food according to any one of claims 1 to 4, wherein the plant food comprises at least one alcohol selected from the group consisting of butyl alcohol, pentyl alcohol, ethylene glycol and glycerin, or the alcohol and water. Freezing method. 6. A refrigerant as ascorbic acid, succinic acid,
At least one selected from the group consisting of citric acid, malic acid, tartaric acid, fumaric acid and dithiothreitol
2. The composition according to claim 1, wherein the content is 0% by weight or less.
6. The method for freezing a plant-based food according to any one of items 1 to 5. 7. The method according to claim 1, wherein the temperature of the refrigerant is -1 ° C. to -50 ° C. 8. A method for thawing a frozen vegetable-based food, comprising:
A method for thawing a frozen plant-based food, characterized by thawing in an aqueous saccharide solution having a concentration of 01 mol / l to 10 mol / l or an aqueous salt solution having a concentration of 0.01 mol / l to 10 mol / l.