Yield and quality of soft tofu as affected by soybean physical damage and storage

Damaged soybeans with 10% and 20% of splits and seedcoat cracks was stored in 85% relative humidity, 30 degrees C for up to 60 days. Samples were taken out at 15-day intervals for analysis and processing. Titratable acidity of soybeans increased significantly but protein extractability from soybean to soymilk decreased significantly with storage time. Soybeans with 20% split and 60 days of storage were not able to form tofu. Yield of tofu decreased significantly beyond 30 days of storage, and 20% split soybeans had a higher loss in yield than 10% split. The changes in color, hardness, and fracturability of tofu were significant (p < 0.05) upon prolonged storage of soybean. Relative amount of glycinin (11S protein) in soybeans increased as storage time increased for all treatments, but beta-conglyciniin (7S) did not change significantly with storage time. Sensory evaluation showed significant off-flavor was produced in tofu made from soybeans stored for 45 days or longer at 85% RH and 30 degrees C.