Method of Preparing Processed Food Material From Soybean

One kilogram of soybean grains was washed with water and soaked for 16 hours in water at room temperature to yield about 2.3 kg of swollen soybean grains. The soybean was then placed in a high pressure tank, to which high pressure steam at 6 kg/cm.sup.2 (by gauge) was introduced and the drains as well as most of the air inside the tank were removed. The inside pressure was then raised to 6 kg/cm.sup.2 (by gauge) with the valve closed, and the pressure was maintained for 30 seconds. Then the steam was stopped and the pressure released, and the soybean was taken out and cooled. Water was removed from the soybean grains which were crushed together with 6 kg of cold or hot water into small granules of less than 0.5 mm diameter. A slurry produced by the crushing was homogenized by one or more treatments in a high pressure homogenizer (Manton-Gaulin Co.) under a pressure exceeding 100 kg/cm.sup.2, to destroy the tissues of soybean. In this treatment cells were broken and the extraction became more complete. The liquid was heated to 75.degree. C, and calcium chloride was added under stirring until a concentration of 0.02 N was reached, to coagulate protein which was then transferred into a frame to make curd from it. The supernatant liquid was removed and the curd was washed with water. Otherwise the coagulum was filtered off with a filtering cloth and further dried by centrifugation with a basket type centrifuge. The yield was about 2.3 kg of coagulum of protein containing 65% of water. This was a processed food material produced from soybean which was free from soybean odor and tasted good. The processed food material could be eaten without further treatment. However, when it was ground with a colloid mill, a pasty product having a fine texture and smooth touch was obtained, of which the composition is as follows:

Grains of soybean in the amount of 1 kg was washed and soaked in 40.degree. C water for 6 hours, producing about 2.3 kg of soybean. This was then treated for 10 seconds with steam which was at about 200.degree. C and at a pressure of 8 kg/cm.sup.2 (by gauge) to deactivate interfering enzymes, and then cooled. The entire amount of the soybean was ground with a colloid mill together with 6 kg of hot water. The obtained slurry was made into finer particles using the same high pressure homogenizer as used in Example 1 with a pressure exceeding 100 kg/cm.sup.2 (by gauge), preferably in the range 300 to 500 kg/cm.sup.2. The desirable particle size is less than 50 micron. The homogenized liquid was kept at 70.degree. C and citric acid was added to adjust the pH to 4.5 to 5.0, to acid-coagulate the protein which, after filtration, was pressed to obtain about 2.7 kg of coagulum having a water content of about 70%. The coagulum was frozen overnight at -10.degree. C to bring about freezing denaturation, and water was removed from the coagulum by pressing it after defreezing. By this treatment about 1.6 kg of a coagulum was obtained, of which the contents were as follows:

A liquid containing very fine particles produced in the same process as in Examples 1 and 2 from whole grains of soybean was kept at 37.degree. C, to which about 2% of a starter was added. The starter is selected from the group consisting of lactobacillus vulgaris, lactobacillus thermophyllus, and streptococcus lactis which were cultured as starter for the lactic acid fermentation. Lactic acid was formed during a 4 to 6 hour standing period. Coagulation followed and the coagulum was broken into pieces as large as soybean grains. Water was removed from the grains by mere standing or pressing, to reduce the water content below 65%. This was ground with a colloid mill. Otherwise removal of water was effected by freezing denaturation, and a paste was produced by kneading with a kneader. This paste was dried into a powder by blowing with hot air or by spraying. The components and their contents in the dried product were as follows: