Abstract:The effects of temperature on the freeze-thaw stability of glycosylated soy protein isolate (SPI) and soy protein isolate hydrolysate (SPH) were investigated. The covalent compounds were prepared by conjugating SPI, SPH and D via heated Maillard reaction, which the products were called as SPI-D and SPH-D respectively. The glycosylation products were determined by using SDS-PAGE, and freeze-thaw stability of emulsion was evaluated by analyzing particle size, degree of coalescence, oil yield, emulsion index and microstructure of emulsion. It can be seen by SDS-PAGE that SPI and D formed a covalent complex by Maillard reaction. In addition, the study indicated that the freeze-thaw stability of all heat-treated samples was improved. Compared with the control, the particle size of the heat-treated emulsion was decreased after three freeze-thaw cycles, the degree of coalescence and oiling off was also reduced. The degree of coalescence of SPI was reduced from 3403.90% of untreated to 348.75% of processed at 90℃, that of SPI-D was decreased from 1181.49% to 191.59%, that of SPH-D was decreased from 806.17% to 138.73%, and the oil yield was also decreased by 62.53%, 43.26% and 42.62%, respectively. With the increase of temperature (30~90℃), the emulsion index of SPI showed a decreasing trend. When the temperature reached 90℃, the emulsion index was decreased by 22.46%, while the emulsion index of SPI-D and SPH-D also showed an overall decreasing trend after heat treatment (30~90℃). It can be observed from the microscope that the heat-treated emulsion that was subjected to three freeze-thaw cycles still had the small size of oil droplets.