Method of preparing processed food material from soybean

Abstract

A method of preparing a processed food material from soybean comprising soaking whole grains of soybean in water, heating the grains at 80 - 200.degree. C with superheated steam for less than a minute to deactivate the physiologically active substances in the soybean, crushing the grains thus treated with water followed by further subdividing into finer particles with a homogenizer to completely destroy the soybean cells, and adding a protein coagulating agent to precipitate the protein together with fat and fibrin.FIELD OF THE INVENTIONThe present invention relates to a method for preparing a processed food material from soybean which tastes good, has no soybean odor, and is smooth in mouth.BACKGROUND OF THE INVENTIONSoybean contains an enzyme which, on being activated, reacts with oil in the soybean grain. The reaction product causes the soybean odor.Soybean also contains tripsin-inhibiting substances and oligosaccharides, which may lead to a flatulence.For this reason, soybean is not a preferred food in the world except in the Far East.SUMMARY OF THE INVENTIONThe present inventors have attempted to eliminate these disadvantages of soybean as a food, and have created a method with which to efficiently remove these drawbacks.Thus, the present inventors have invented a process for efficiently converting soybean into a processed food material. The features of the present invention lie in the method of preparing a processed food material from soybean comprising soaking whole grains of soybean in water, heating the grains at 80 - 200.degree. C with superheated steam for less than a minute to deactivate the physiologically active substances in the soybean, crushing in cold or hot water followed by further subdividing into finer particles with a homogenizer to completely destroy the soybean cells, adding a protein coagulating agent, such as, acid and salts of calcium to precipitate the protein together with fat and fibrin, the mixture being either curded to obtain a pasty product or dehydrated by freezing or heating to obtain a dried powdery product.DETAILED DESCRIPTION OF THE INVENTIONAccording to the present invention, soaked grains of soybean are treated in a high pressure tank by introducing steam at high temperature and high pressure, for example at 165.degree. C and 6 kg/cm.sup.2, for less than a minute. In this treatment the enzyme and the tripsin-inhibiting substances are denatured to deactivation, which is useful to remove the source of soybean odor, as well as to soften the skin of the beans. But, if the heating at a high temperature under a high pressure continues for more than a minute, the beans take on the smell and taste of boiled beans which is not favorable. Therefore the grains of soybean treated at a high temperature and pressure for a short time, are removed from the tank and then cooled in water. This treatment serves to avoid the boiled bean smell and taste.Next, the grains of soybean are divided into finer pieces.From the crushed soybean grains the outer skins and cell membranes are separated from the soybean milk by filtration or any other suitable method, forming a solid residue called "okara".When soybean curd, which is called "tofu" or frozen dried soybean curd is prepared, the amount of the components utilized remains less than 50% of the total soybean grains, and the solid residue contains more than 20% of the protein and more than 6% of the fat oil. To improve the yield of protein, fat, and oil, the solid residue is further crushed in cold or hot water and then subdivided with a homogenizer under a high pressure greater than 100 kg/cm.sup.2 to destroy any cells remaining in the residue.This treatment gives a stable colloidal liquid of soybean in which the cells are broken and the cell membranes are divided into tiny particles. However, oligosaccharides in the soybean are dissolved in the liquid, which may cause flatulence. To remove the oligosaccharides, a coagulating agent selected from the group consisting of edible acids, such as, lactic, citric, malic, and phosphoric acids or salts thereof, salts of calcium or magnesium, such as, calcium chloride, magnesium chloride, calcium sulfate, magnesium sulfate, or other coagulating agents, such as, glucono-.delta.-lactone are added, to coagulate the protein leaving the oligosaccharides in the supernatant liquid which is removed as a waste.The coagulated matter thus obtained is then optionally washed with water and utilized as a processed food material. The water content may be reduced if necessary.If a product of lower water content is desired, dehydration by means of freeze drying or heating is feasible. The product is free from the soybean odor, contains no physiologically interfering material, and has good taste. It may be utilized in a variety of uses including food processes in the agriculture, fishery, cattle breeding, and dairy areas.

Description

Claims

1. A method of preparing a food material from soybean comprising swelling the beans by soaking whole grains of soybean in water, heating the swollen grains at 80 to 200.degree. C with superheated steam for less than a minute to deactivate the enzyme and tripsin inhibiting substances therein, crushing the grains thus treated in sufficient amount of water to dissolve flatulence producing saccharides followed by further subdividing into finer particles with a homogenizer to completely destroy the soybean cells and adding a protein coagulating agent in amounts sufficient to precipitate the protein together with fat and fibrin.

2. A method according to claim 1 which further comprises curding the mixed precipitate to obtain a pasty product.

3. A method according to claim 1 which further comprises dehydrating the mixed precipitate to obtain a dried powdery product.

4. A method according to claim 1 in which the protein coagulating agent is one selected from the group consisting of edible acids, salts thereof, and salts of calcium or manganese.

5. A method according to claim 3 in which the dehydration is effected by freeze drying.

6. A method according to claim 3 in which the dehydration is effected by heating.