Physicochemical properties and in vitro starch digestibility of wheat starch/rice protein hydrolysate complexes

In this study, wheat starch (WS) and rice protein hydrolysates (RPHs) RPH2 and RPH4 were subjected to hydrothermal treatment to explore the interaction between the two and the relationship between this interaction and starch digestibility in vitro. Rice protein hydrolysates limit the hydration and expansion of starch, increase the gelatinization temperature and decrease the gelatinization enthalpy. The addition of hydrolysates showed a potent ability to mitigate starch digestion. Compared with the content of WS, the contents of the slowly digested starch and resistant starch in the WS-12%RPH4 complexes increased from 31.4% and 36.1%to 33.3% and 46.7%, respectively. RPH2 and RPH4 had similar but different effects on starch properties. RPH changed the water distribution by affecting the interactions between starch molecular chains, resulting in changes in the gel network. The recrystallization of starch molecules was inhibited by the addition of 4% and 8% RPH, while 12% RPH promoted defective but extensive co-crystallization. The phase separation induced by 20% RPH addition enhanced the interaction between amylopectin chains.