Polyphenols from pigmented quinoa as potential modulators of maize starch digestion: Role of the starch-polyphenol inclusion and non-inclusion complexes

This study aimed to investigate the interaction modes between maize starch (MS) and quinoa polyphenols (QPs) under hydrothermal treatments and its influence on the multi-scale structure and digestive behaviors of MS through mechanistic analyses. Thermodynamic and microscopic results revealed that during starch gelatinization , the starch chains interacted with QP polyphenols to form new aggregates with retarded gelatinization. The X-ray diffraction and 13 C nuclear magnetic resonance spectroscopy further confirmed the presence of both V-type inclusion complexes and non-inclusion complexes in QP-complexed MS. Through multiple spectroscopic approaches, it was demonstrated that complexation with QPs promoted the formation of local helical and short-range ordered structures and crystallization in MS and led to resistance of the starch chains to digestive enzymes. As a consequence, the MS–QP complexes showed substantially reduced digestion rates with increases in the contents of resistant starch and slowly digestible starch, as well as lower values of the predicted glycemic index . Compared to white quinoa polyphenols, polyphenols from red and black quinoa displayed a greater efficiency in modulating the starch structure and digestive properties. This study provides a valuable basis for the application of pigmented quinoa polyphenols as functional ingredients in starchy foods with desired glycemic response.