Valorization of watermelon rind as a modulator of starch digestibility in waffles: Nutritional and functional...

This study evaluates the valorization of watermelon rind powder as a functional ingredient in waffles, given its high fiber and phenolic content. Waffles were chosen as a suitable matrix given their wide consumption and ability to incorporate functional ingredients without compromising acceptability. Incorporation of rind powder increased protein, dietary fiber, and phenolic compounds by 19%, 122.5%, and 34.5%, respectively. Enriched waffles showed reduced in vitro starch digestibility, with resistant starch increasing by 87.5%, likely due to starch-polyphenol and starch-fiber interactions that limit enzymatic accessibility. FTIR analysis (1047/1022 cm^-1 ratio) supported this mechanism by revealing enhanced short-range ordered starch structures (0.65 to 0.96). Although phenolic bioaccessibility after simulated digestion was relatively low, a stable fraction remained, suggesting potential colonic release. Overall, watermelon rind powder improves the nutritional, functional, digestive, and technological properties of waffles and represents a promising strategy for valorizing agro-industrial by-products within a circular-economy framework in food products.