The anti-digestibility mechanism of soy protein isolate hydrolysate on natural starches with different crystal types

The effects of soy protein isolate hydrolysate (SPIH) on the physicochemical properties and digestive characteristics of three starch types (wheat, potato, and pea) were investigated. Fourier-transform infrared spectroscopy and molecular dynamics simulations showed that hydrogen bonds were the driving force of the interaction between SPIH and starch. Furthermore, the SPIH was predicted to preferentially bind to the terminal region of starch using molecular dynamics simulations. Compared to pure starch, adding 20 % SPIH to wheat starch, potato starch, and pea starch, the content of resistant starch increased by 39.71 %, 125.66 % and 37.83 %, respectively. Both the radial distribution function (RDF) and low field-nuclear magnetic resonance (LF-NMR) showed that SPIH reduced the flow of water molecules in starch, indicating that SPIH competed with starch for water molecules. Multiple characterization experiments and molecular dynamics simulations confirmed that the anti-digestibility mechanism of SPIH on natural starches with different crystal types could be attributed to the interaction between starch and SPIH, which decreased the catalytic efficiency of amylase. This study clarified the anti-digestibility mechanism of SPIH on natural starches, which provides new insights into the production of low-glycemic index foods for the diabetic population.