Glycation of whey protein isolate and stachyose modulates their in vitro digestibility: Promising prebiotics as functional ingredients

Glycated conjugates have recently been designed to be targeted to probiotic in the colon. However, the underlying mechanisms of regulating the prebiotic properties and digestibility of conjugates through glycation have not been fully elucidated. In this study, WPI-stachyose conjugates were prepared through Maillard reaction and proposed as functional ingredients with prebiotic characteristics. The effect of glycation on the in vitro simulated gastrointestinal fate of WPI-stachyose conjugate was further evaluated. The results showed that the glycated conjugates of stachyose covalently bound to whey protein exhibited a characteristic cross-linked structure, which enhanced their inhibition of α-amylase activity and retardation of glucose dialysis. Besides, simulated digestion analysis demonstrated that stachyose-conjugated WPI was more resistant to pepsin and trypsin digestion than unconjugated WPI. Compared with native WPI, the protein digestibility and degree of hydrolysis of WPI-stachyose conjugates were reduced by 12.5% ± 0.66% and 5.30% ± 1.02%, respectively. In addition, rat intestinal extracts were used to detect the in vitro digestibility of stachyose. The hydrolysis rate of stachyose in the glycated conjugates was 70% lower than that of stachyose. Therefore, the resulting WPI-stachyose conjugate may be used as functional ingredients to achieve the sustained-release effect in the gastrointestinal tract. These findings demonstrate the possibility of modulating proteins and carbohydrates digestibility through glycation, and have implications for the design and manufacture of potential prebiotic molecules with controlled digestibility in food and related healthcare fields.