Improving the freeze-thaw stability of soy protein emulsions via combing limited hydrolysis and Maillard-induced glycation

The investigation of limited hydrolysis combined with Maillard-induced glycation on improving the freeze-thaw stability of soy protein isolate (SPI) was carried out. Soy protein isolate hydrolysate (SPH) was first prepared by trypsin, with a hydrolysis degree of 2% and 5%. Afterwards, SPI and SPH were conjugated with dextran to form a covalent complex macromolecule, which were named SPI-D, SPH2-D and SPH5-D, respectively. Covalent bond was formed between SPI/SPH and dextran molecules via the glycation reaction has been confirmed by fourier transform infrared (FTIR) spectroscopy analysis. Subsequently, the freeze-thaw stability of SPI-D and SPH-D was evaluated. After three freeze-thaw cycles, the characters of SPH-D emulsions exhibited smaller values than those of SPI-D emulsions in terms of oiling off, particle size, flocculation degree (FD) and coalescence degree (CD). In addition, SPH2-D emulsions were more stable after freeze-thaw treatment compared with SPH5-D emulsions. Optical microscopy analysis also supported the results above.