Low digestibility characteristics of white kidney bean protein hydrolysate-corn starch complex: Structural and functional transformations induced by heat-moisture treatment

This study prepared complexes using corn starch and white kidney bean protein (KBP) and its hydrolysates (KBPH60 and KBPH180, hydrolysates derived via enzymatic hydrolysis for 60 and 180 min, respectively) through heat-moisture treatment (HMT). The impact of HMT on the structure, physicochemical properties, and in vitro starch digestibility of these KBP/KBPH-starch complexes was systematically analyzed. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed that KBP and its hydrolysates stabilized the starch structure weakened by HMT through hydrogen bonding, promoting a more ordered crystalline arrangement and decreasing starch digestibility. Scanning electron microscopy (SEM) confirmed that HMT promoted the encapsulation of starch granules by KBP/KBPH, acting as a barrier to amylase. Both HMT and KBP/ KBPH inhibited starch gelatinization, reducing paste viscosity and disrupting the starch gel network. This increased free water content and softened gel texture. HMT intensified these effects, increasing resistant starch (RS) content. KBPH, particularly HMT-KBPH180-S (heat-moisture treated complex of KBPH180 and corn starch), exhibited a pronounced inhibitory effect on starch digestibility, yielding the highest RS content. These results provide new insights into regulating starch digestibility and stability through protein hydrolysates and HMT, laying a theoretical foundation for the developing functional foods with low digestibility.