Application of Wet Glycosylation Modified Soybean Protein Isolate in Hypo-allergenic Chiba Tofu

Two monosaccharides, glucose and xylose, were used as glycosyl donors to investigate the effects of reaction time, reaction temperature, protein-to-sugar ratio and protein concentration on the wet glycosylation reaction of soybean protein isolate. The allergenicity of SPI-glucose derivative (SPI-glucose) and SPI-xylose derivative (SPI-xylose) was analyzed. SPI-glucose and SPI-xylose were used to produce the hypo-allergenic Chiba tofu. The results showed that xylose was more likely to glycosylate with SPI than glucose, but it was also more likely to produce melanoidin. The highest degree of glycosylation reaction was observed at the protein concentration of 25 mg/mL. The degree of glycosylation reaction was positively correlated with the reaction temperature, reaction time, and the amount of sugar added. The results of SDS-PAGE and fourier transform infrared spectroscopy showed that glycosylation caused covalent binding of SPI and sugar molecules, and the free amino group content of SPI was reduced. The degree of glycosylation reaction was negatively correlated with the allergenicity of SPI, and the allergenicity of SPI-xylose could be reduced by up to 50%. Chiba tofu made from SPI-xylose using glutamine aminotransferase (TGase) had good elasticity and chewiness.