The Influence of Polyphenols on Starch Structure Across Molecular, Chemical, and Microstructural Levels

Despite the well-documented effects of polyphenols on the nutritional properties of starch, information regarding the structure of starch–polyphenol complexes remains limited. Therefore, this study aimed to investigate the molecular, chemical, and microstructural properties of starch-polyphenol complexes prepared from wheat, rice, potato, and maize starches. Apparent amylose content was determined spectrophotometrically, molecular interactions were analyzed using Fourier Transform Infrared (FTIR) spectroscopy, and morphological changes were evaluated by scanning electron microscopy (SEM). Significant differences in apparent amylose content were observed following the incorporation of selected polyphenols, especially epigallocatechin gallate. FTIR analysis suggested that polyphenols may alter the molecular organization of starch matrices through non-covalent interactions, predominantly hydrogen bonding. Epigallocatechin gallate and quercetin exerted more noticeable effects than the other polyphenols studied. Furthermore, SEM observations performed exclusively on starch systems containing epigallocatechin gallate revealed noticeable morphological alterations in native starch granules following in vitro digestion compared with undigested controls. These findings provide new insights into the formation of starch-polyphenol complexes and support their potential application in the development of functional foods with improved nutritional properties.