Changes of gelation behavior, water distribution and digestibility of protein-starch mixtures in the oat dough/batter model affected by water

The interactions between protein and starch in the oat dough/batter system during heating are particularly important for oat-based products but are rarely understood. In this study, the gelation behaviors and digestibility of oat protein-oat starch mixtures after heat treatment and their gelling properties in the oat dough/batter model corresponding to water content ranging from 50% to 80% were determined. Under the same water content, the oat protein-starch samples exhibited higher G′ and G″ values during the gelatinization process and lower gelatinization enthalpy (ΔH) than the oat starch samples. At low water content (oat dough system), competitive hydration between oat protein and starch played a dominant role, and protein inhibited the retrogradation behavior of starch. When the water content increased to 80% (oat batter system), the protein significantly promoted starch retrogradation behavior with ΔH values increasing from 0.54 to 1.71 J/g. The addition of protein weakened the tight binding between starch and water molecules and enhanced the mobility of water in the system. The interaction between oat protein and starch inhibited the enzymatic hydrolysis and slowed starch digestion, which was mainly related to the formation of resistant starch in the oat protein-starch gels system.