Structural, physicochemical, and digestive properties of starch-tannic acid complexes modulated by co-heating temperatures

The effect of co-heating temperature on the functional features of tannic acid-starch complexes has been a research gap in the field of food processing. In this study, tannic acid-corn starch (TA-CS) complexes were co-prepared at different temperatures (25, 50, 70, and 95 °C), and their structural, physicochemical, and digestive properties were examined. Results from High-Performance Liquid Chromatography (HPLC) and DPPH radical scavenging indicated that higher preparation temperatures led to increased binding between TA and CS, resulting in stronger antioxidant properties of TA-CS complexes. Iodine Binding Capacity (IBC), X-ray Diffraction (XRD), and Fourier Transform Infrared (FT-IR) results revealed that, at elevated preparation temperatures (50, 70, and 95 °C), TA and CS form V-type complexes mediated not only by hydrogen bonding but also by hydrophobic interactions. Differential Scanning Calorimetry (DSC) results showed that with increasing TA concentration, complex gelatinization was promoted at 25 °C and 50 °C but inhibited at 70 °C and 95 °C. Thermogravimetric Analysis (TGA) indicated that higher preparation temperature (95 °C) was detrimental to the enhancement of CS-TA thermal stability. In vitro digestion results demonstrated that complexes prepared at 70 °C and 95 °C exhibited stronger resistance to digestion, displaying higher blood glucose control levels and nutritional value compared to those prepared at 25 °C and 50 °C. This study enhanced our understanding of the impact of co-heating temperatures on CS-TA interactions, providing new insights for developing health-oriented starch-based foods utilizing polyphenols.