Processing Strategies to Enhance the Structural and Functional Properties of Proteins From Sweet Potato By-Products

Sweet potato by-products are a potential source of proteins and phenolic compounds with valuable functional properties. However, enzymatic browning driven by polyphenol oxidase (PPO) limits their stability and utilization. In this study, processing conditions were designed to achieve controlled partial PPO inactivation using ascorbic acid (AA), sodium metabisulfite (MB), and a combined ascorbic acid and mild heating treatment at 50°C (AB50), compared with a control sample that did not receive any anti-browning treatment. The effects of these treatments on the structural, emulsifying, and antioxidant properties of sweet potato protein extracts were evaluated. AA treatment altered protein secondary structure and improved emulsifying activity despite reducing protein solubility. MB promoted higher antioxidant activity, associated with increased protein and phenolic contents. FTIR analyses showed changes in functional groups, suggesting protein-phenolic interactions that contributed to the structural modifications observed after treatment. Among the treatments, AB50 showed the best overall performance, enhancing emulsifying properties (EAI 14.86 vs 7.56 m²/g from CT), improving emulsion stability, and increasing antioxidant capacity. These effects were associated with protein structural rearrangements, including changes in surface charge and free sulfhydryl content. Overall, the results demonstrate that AB50 can replace sodium metabisulfite while enhancing the functional properties of sweet potato protein extracts. Therefore, controlled processing represents a promising strategy for adding value to sweet potato by-products as multifunctional food ingredients.