Abstract:

Soybean protein isolate (SPI) and lactose were used as raw materials to synthesize SPI-lactose graft by solventfree
glycosylation with microwave heating and SPI-lactose-Al2O3 graft using Al2O3 as the carrier. The chemical and structural
properties of the two graft copolymers including color, fluorescence spectral characteristics, amino acid composition,
solubility and degree of browning were compared. Results showed that the reaction rate of SPI-L-alumina was lower than
that of SPI-L. With the extension of microwave heating time, the color of both samples were deeper, and color difference
gradually increased, the solubility rose first and then dropped, and the contents of lysine and arginine were significantly
reduced. The maximum fluorescence wavelength of SPI-L revealed a blue shift followed by a red shift with an initial
increase and then a decrease in relative fluorescence intensity, whereas the maximum fluorescence wavelength of SPI-Lalumina
displayed a blue shift with a gradual increase in relative fluorescence intensity.

Key words: soybean protein isolate (SPI), lactose, microwave, graft, physicochemical properties