Starch digestion retarded by wheat protein hydrolysates with different degrees of hydrolysis

[Display omitted] •Wheat protein hydrolysates (WPH) retarded the digestion of rice starch.•WPH (pepsin hydrolysis for 60 and 120 min) formed more hydrogen bonds with starch.•WPH (pepsin hydrolysis for 60 min) made the aggregate structure of starch denser. Wheat protein hydrolysates (WPH) were prepared by pepsin hydrolysis for 30, 60, and 120 min (WPH30, WPH60, and WPH120). The mixed system of rice starch and WPH was hydrothermally treated to explore the effect of WPH with different degrees of hydrolysis on starch digestion. WPH reduced the first-order rate coefficient (k) of starch digestion. Especially, WPH30 reduced the k value the most and formed the highest slowly digestible starch content due to the entanglement of starch chains and long-chain peptides. WPH60 and WPH120 with more hydrophobic peptides and polar amino acids than WPH30 tended to form hydrogen bonds with starch molecules due to less steric hindrance. Particularly, the complexation of WPH60 promoted the formation of dense aggregate structure and hindered the enzymatic hydrolysis of starch to a certain extent, thereby increasing the resistant starch content. These findings provide significant guidance for the preparation of hypoglycemic reformed food.