Modulation of starch-polyphenol complex thermal stability and antioxidant activity: The role of polyphenol structure

Polyphenols are closely related to human health, but thermal treatment causes the loss of polyphenol activity. Complexation between amylose and polyphenol prevents oxidation and degradation of polyphenols during thermal treatment. And the functional properties of the complex are affected by the polyphenol backbone. Therefore, this study compared the complexation between pre-formed V-amylose (V_6a) and polyphenols with different backbones (C6-C1, C6-C3, and C6-C3-C6). Specifically, a non-inclusion complex was formed between V_6a and PHBA through intermolecular hydrogen bonding, whereas p-coumaric acid (PCA, C6-C3 backbone) and 6-hydroxyflavone (HF, C6-C3-C6 backbone) formed V-type inclusion complexes with V_6a. In addition, V_6a-PCA possessed greater relative crystallinity (42.70 %), higher thermal stability (136.2 °C), higher encapsulation efficiency (22.8 %), and stronger antioxidant activity (2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity = 62.80 %). Finally, the molecular dynamic simulation corroborated the effect of the polyphenol backbone on the complex type. This study suggested that C6-C3 backbone polyphenols facilitated the formation of inclusion complexes with V-amylose compared to hydrophilic C6-C1 backbone polyphenols and C6-C3-C6 backbone polyphenols. V-type inclusion complexes are effective encapsulation carriers, which can be used in the future to enhance the bioactivity of polyphenols in food processing.