Evaluation of quality characteristics, antioxidant activity, functional groups of sweet potato by-products and their usage in sandwich bread processing

A substantial quantity of waste is generated during sweet potato processing, posing environmental and economic challenges. This study aimed to valorize sweet potato by-products (SPB) by drying and milling them into powder and incorporating the material into sandwich bread formulations as a partial replacement for wheat flour at levels of 10-25% (corresponding to formulas B1 to B4) along with control sample B0. The physicochemical, structural, and functional properties of SPB powder were evaluated to determine its suitability as a functional ingredient. The results indicated that SPB powder possesses high nutritional value, with considerable amounts of dietary fiber, bioactive compounds, and strong antioxidant activity. Scanning electron microscopy revealed predominantly oval and polygonal particles with relatively smooth surfaces and intact structures. Fourier-transform infrared spectroscopy confirmed a polysaccharide-rich lignocellulosic composition, including starch, cellulose, hemicellulose, and phenolic compounds. Among the tested formulations, bread containing 15% SPB (B2) was identified as optimal, as it maintained desirable moisture content, loaf volume, and color characteristics while significantly enhancing nutritional quality. Compared with the control, the B2 formulation showed substantial increases in dietary fiber and total polyphenols. These findings highlight the potential of SPB powder as a sustainable, high-fiber functional ingredient for bakery product fortification.