1989 Volume 36 Issue 3 Pages 231-236
A supernatant of coagulated soymilk obtained during Tofu processing have been te rmed Yu in Japanese, and have been main waste water of Tofu factory. Because Yu has been suggested to contain noncoagulated protein and sugers, the recovery of protein from Yu is expected to be effective for reduction of waste water facilities and the recover ed protein should be utilized as food materials. Therefore, the yield, nitrogen content and protein composition and its molecular weight distribution on gel electrophoresis of the Yu solid were examined. Fractionation by gel filtration and ultrafiltration was also studied. As a result, into Yu moved 5.7% of soybean's solid materials, and the nitrogen content of the Yu solid was 5.1% (31.9% as protein). On a gel electrophoretical pattern at least 7 kinds of protein components were detected, of which main three components were deduced to have the molecular weight of 55, 38 and 15.5kD, respectively. The gel electrophoretical pattern of Yu was quite different from that of a soybean whey fraction (supernatant fraction of isolated protein from defatted soybean meal) which have been investigated in detail. Yu was able to divide into protein and nonprotein fractions by gel filtration with a Bio gel P-30 or P-100 column, ultrafiltration with a 10kD filter and dialysis with cellophane tube. Further, about 60% of the protein fraction was successfully recovered from waste Yu water of Tofu factory by dialysis and ultrafiltration.
