JPS6216625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing frozen tofu, which becomes tofu with excellent texture upon thawing, and its purpose is to provide a nutritional food with excellent preservability. Another purpose is to provide a material that, after drying, can be rehydrated in water or hot water to produce tofu having an excellent texture.

Tofu is a protein food that has been widely used as a traditional Japanese food since ancient times, but its shelf life is extremely poor due to its high moisture content. Various studies have been conducted to improve the shelf life of tofu, including improvements to packaging methods, but no fundamental solution has been found. Generally, methods such as freezing or drying are used to improve the shelf life of foods, but it is a well-known fact that when this method is applied to tofu, it transforms into another food such as frozen tofu. That is, when tofu is frozen, soybean protein, the main component of tofu, undergoes freezing denaturation and becomes organized into layers, so even when thawed, it does not retain the smooth texture of tofu before freezing. This fact is used in the production of frozen tofu, and it is well known that even if tofu is frozen and dried and rehydrated, it will not return to its pre-frozen state.

The present inventors conducted various studies with the aim of obtaining frozen tofu that has an excellent texture when thawed, and found that after adding water to soy milk powder and dissolving it, tofu was prepared using a conventional method. However, when starch and/or carbonate are dissolved in the aqueous solution of soy milk powder, the protein does not form layers even after freezing, and when thawed it has a supple, crisp, and excellent texture. Furthermore, they discovered that if the obtained frozen tofu is dried, it can be rehydrated in water or hot water to produce tofu of similar quality, and the present invention was completed.

The starches used in carrying out the method of the present invention include raw starches such as potato starch, wheat starch, corn starch, and waxy corn starch, or various processed starches thereof, such as alpha starch, oxidized starch, and dextrin starch. Decomposition products, starch derivatives such as starch esters, starch ethers, cross-linked starches, etc. are used. These starches have almost the same effect regardless of their type, but α-starch is particularly preferred as it provides high-quality frozen tofu. On the other hand, as the carbonate, alkali metal carbonate salts such as soda carbonate and sodium bicarbonate are advantageously used. The amount of these additives does not need to be used in large quantities, and may vary slightly depending on the type, or the amount of protein in soy milk or emulsion (in terms of pure protein)
1 part by weight (hereinafter, all parts are by weight), in the case of starches, 0.02 to 1 part, preferably
The effect is expressed at 0.1 to 0.5 parts, and in the case of carbonates, 0.01 to 0.05 parts, preferably 0.02 to 0.04 parts. or,
When both are used in combination, it is particularly advantageous to use each within the above range, as the effect is greater than when used alone.

Of course, when used together, the amount used may be less than the above range.

When carrying out the method of the present invention using soymilk as a starting material, the above-mentioned additives are added to the soymilk and homogenized, and then calcium salt, magnesium salt,
A known tofu coagulant such as glucono delta lactone may be added to coagulate the tofu to produce tofu for frozen processing. The raw soymilk used is one produced by adding water to soymilk powder in a conventional manner.

The tofu for freezing thus obtained is then frozen using a freezer, air blast, liquid nitrogen, etc., and the freezing temperature is -80°C to -10°C, preferably -60°C to -40°C. Rapid flash freezing is preferred in order to suppress freezing denaturation and to obtain high quality frozen tofu.

The present inventors further researched the present invention and found that in addition to the additives used in the present invention, gums such as xanthan gum, carakeenan, guar gum, locust bean gum, and gum arabic: glycerin, sorbitol, propylene glycol Wetting agents such as ascorbic acid, erythorbic acid, sulfite, etc.
It has been found that the texture of tofu after thawing can be further improved by using cysteine, homocysteine, alginic acid, salts thereof, carboxymethyl cellulose, especially gum, in combination with the above-mentioned additives.
For example, in the case of gum, the effect will vary slightly depending on the type, but the effect will be achieved at 0.001 to 0.5 part, preferably 0.01 to 0.1 part, per part of raw protein (in terms of pure protein).

Furthermore, it has been found that when the frozen tofu according to the present invention is dried under vacuum, reconstitution of the obtained dried product with water or hot water does not result in so-called frozen tofu, but tofu with excellent texture can be obtained. When the product of the present invention is used as dried tofu, which is more advantageous in terms of storage, the second additive, especially ascorbic acid, erythorbic acid, or an alkali metal salt thereof, can be used in combination to significantly improve the reconstitution properties of dried tofu and to moisten it. By using the agent in combination, damage such as cracking can be effectively prevented during drying and during storage and transportation in a dry state.

The amount of these used varies depending on the type, but there is no need to use large amounts; for example, ascorbic acid, ersorbic acid, or their salts should be used in the range of 0.001 to 0.01 part per part of raw protein (in terms of pure protein), and as a wetting agent, it should be used in large amounts. The effect can be obtained sufficiently by using 0.001 to 0.5 parts.

As is clear from the above description, the present invention provides a method for producing frozen tofu, which has been considered difficult in the past, and greatly contributes to the food industry.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Add 2000 dl of water to 200 g of tofu powder (Nippon Protein Industries Co., Ltd. "Hyproton") and 20 g of α-waxy cornstarch, dissolve, and then heat until boiling for 15 minutes with gentle stirring to about 25°C. It was cooled to Next, 6 g of glucono-delta-lactone was added, and after casing, the mixture was heated and coagulated in a hot bath at 85° C. for 50 minutes. The coagulated product was frozen at -40°C to obtain frozen tofu.

When thawed after being stored at the same temperature for 30 days, it had a slightly firm texture and color similar to firm tofu.

Example 2 2000 ml of water was added to 200 g of tofu powder ("Hyproton" manufactured by Nippon Protein Industries, Ltd.), 0.3 g of heavy carbon soda, and 30 g of carrageenan, and the same treatment as in Example 1 was performed to obtain frozen tofu. When it was stored at -40°C for 30 days and thawed, it had the smooth texture and color of silken tofu.

When this frozen tofu was vacuum dried, dried tofu was obtained. When this product was rehydrated in hot water, it returned quickly and gave tofu with excellent flavor and texture.

Example 3 200 g of tofu powder (“Hyproton” manufactured by Nippon Protein Industries, Ltd.), 10 g of dextrin (“Pine Dex” manufactured by Matsutani Chemical Co., Ltd.), 0.2 g of bicarbonate of soda, and 2000 g of water.
ml was added and dissolved, then boiled for 15 minutes and cooled to 25°C. Next, 6 g of glucono delta lactone was added, and after casing, the mixture was heated and coagulated in a hot bath at 85° C. for 50 minutes. Then, it was instantly frozen at -60°C to obtain frozen tofu.

When this product was stored at -35°C for 6 months and thawed, it exhibited the texture and color of silken tofu, and had a smoother texture than that obtained in Example 1.

Claims (1)

[Claims] 1 0.02 to 1 part by weight of soy milk powder (converted to pure protein)
A method for producing frozen tofu, which comprises dissolving in water a mixture of part by weight of starch and/or 0.02 to 0.05 part by weight of carbonate, preparing tofu by a conventional method, and then freezing.