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

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.