Effect of transglutaminase on rennet-induced gelation of skim milk and soymilk mixtures

BACKGROUND Protein gels made from cow milk and soymilk can yield products of exceptional value. Transglutaminase (TG) affect rennet-induced gelation of proteins, and improves the functionality of the final products. In this paper, TG and rennet were added to skim milk and soymilk mixtures simultaneously, and the rennet-induced coagulation was studied. Diffusing wave spectroscopy and rheology measurements were used to access the structural changes of the mixtures during renneting. Syneresis analysis and microscopy can give more information for understanding the system. RESULTS Soymilk and TG have synergetic effects and inhibit rennet-induced gelation to a certain degree. With increasing soymilk and TG, elastic index and storage modulus decreased, gelation time was delayed, and curd yield and moisture content increased. At excess soymilk and TG, no curds can be formed. There were significant effects of soymilk and TG on curd microstructure. Soymilk inhibited the aggregation of casein micelles and contributed to more coarse and heterogeneous networks. TG limited reorganization of the proteins, leading to more homogenous networks with small pores. CONCLUSION The use of soymilk and TG simultaneously impair rennet-induced gelation and curd syneresis, and consequently lead to a higher yield of high-moisture curd. (c) 2018 Society of Chemical Industry