Formation of Soybean Milk Curds by Lactic Fermentation and Their Ripening

Abstract

Soybean milk was coagulated by lactic fermentation using Streptococcus thermophilus(T), Streptococcus lactis(L)or a mixture of T and L without addition of calcium as a coagulant. The curds obtained were ripened by Penicillium caseicolum. As a result of rising the acidity at early stage of the ripening, pH of curds could nearly maintain 6.5 after 2 week's ripening. Increase of water soluble nitrogen after 1 week's ripening was so rapid that 3 week's ripening rate reached more than 80%. The contents of total free amino acids in TL sample increased in 1150mg/100g after 3 week's ripening. Amino acids liberated comparatively high amounts were glutamic acid, aspartic acid, lysine and so on. To prevent rapid progress of the ripening during the short term, the curd was coated with parafin after eliminating mold from surface, and then ripened at lower temperature(5°C). This treatment was effective to control the ripening. Trypsin inhibitor(TI)activity did not change during the ripening and it was found that most of TI activity was originated from whey remaining in curds.