The Mechanism Of Soy Protein Coagulation Induced By Papain

Mechanism of soy protein coagulated by papain was investigated.The main components in soy protein isolate are 7S and 11S globulins. Studiesof papain on 7S, 11S and mixture of the two proteins suggested that 11S is themain component in SPI to form coagulation. 7S coagulation required higher papainaddition than 11S coagulation, while 11S gel's elastic modular was higher than7S gel. The elasticity of mixture depended on the proportion of 11S.Two proteinases were separated from papain by SP-sepharose cation-exchangechromatography. The coagulating effect of the two proteinases and their mixtureon 7S and 11S was compared. Results indicated that two proteinases interacted witheach other during the coagulating process. 11S gel induced by mixture of twoproteinases was more elastic, and 7S gel induced by separated proteinase was moreelastic. The molecular weight distribution of 7S and 11S coagulation revealed thatsmall fragments contributed to the gel structure.The effect of papain concentration and temperature on the coagulation of 11Swas discussed. The papain concentration determined hydrolyzing rate and so todetermine coagulating rate. At the same papain concentration, the higher thecoagulating temperature, the lesser elastic modular and phase angle the 11S gelshowed. This indicated that hydrophobic interactions were involved in theformation of 11S gels and results of various reagents on the solubility of 11Sgel coagulated by papain supported the same conclusion. The DH (degree ofhydrolysis) of 11S coagulation was about 6%. The molecules' weights were mainlyin 12300-34500Da and 500-4600Da ranges in 11S gel.