Effect of exogenous protein crosslinking on the physicochemical properties and in vitro digestibility of corn starch

Starch is a primary energy source of human diet. Its physicochemical properties and digestibility can be improved by incorporating exogenous protein. In this study, mung bean protein isolate was covalently crosslinked using transglutaminase and proanthocyanidin to create crosslinked mung bean protein isolate. This modified protein was combined with corn starch to form crosslinked mung bean protein isolate-corn starch composite samples. Results demonstrated that these composite samples exhibited superior physicochemical properties, including reduced swelling capacity, enhanced freeze-thaw stability, improved thermostability, and enhanced antioxidant properties. During in vitro digestion, the improved corn starch digestibility was attributed to two factors: first, hydrogen bonding and electrostatic interactions between crosslinked mung bean protein isolate and corn starch; and second, the synergistic crosslinking of transglutaminase and proanthocyanidin promoting the formation of a stable protein network of mung bean protein isolate, serving as a physical barrier to protect corn starch. After co-treatment with transglutaminase and proanthocyanidin, significant changes of mung bean protein isolate occurred in their secondary and tertiary structures, enhancing its protein network strength, thereby improving the physicochemical properties of corn starch. These findings propose a new strategy for reducing rapidly digestible starch and provide a theoretical foundation for developing low glycemic index starch foods.