Structural and Physicochemical Properties of a Chinese Yam Starch–Tea Polyphenol Complex Prepared Using Autoclave-Assisted Pullulanase Treatment

Interactions between food components have a positive impact in the field of food science. In this study, the effects of tea polyphenol on the structural and physicochemical properties of Chinese yam starch using autoclave-assisted pullulanase treatment were investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, rapid visco analysis, differential scanning calorimetry, and the 3,5-dinitrosalicylic acid method were applied in this study. The results showed that the Chinese yam starch–tea polyphenol complex formed a structural domain with higher thermal stability along with lower pasting viscosities than native starch. The in vitro digestibility of Chinese yam starch decreased with the addition of the tea polyphenol, and the amount of resistant starch content in the complex was 56.25 ± 1.37%, significantly higher than that of native starch (p < 0.05). In addition, the complex showed a B+V-type crystalline structure, which confirmed that the interaction modes between the starch and tea polyphenol include hydrogen bonding and hydrophobic interactions. Moreover, the appearance of an irregular sponge network structure of the complex further supported the interactions between the starch and tea polyphenol. This study provides a theoretical basis for the development of functional foods using Chinese yam starch.