Structure-function insights into heat/pH-shift-treated legume protein-EGCG conjugates as functional alternative...

Walnut oil is rich in polyunsaturated fatty acids with health benefits, but its susceptibility to oxidation limits its application. This study explored antioxidant emulsifiers based on soy protein (SP), pea protein (PP), and chickpea protein (CP) as plant-derived alternative proteins, treated by heat and pH-shift, then grafted with epigallocatechin gallate (EGCG). EGCG served as a natural antioxidant to enhance emulsion stability. Emulsions stabilized by treated proteins (TSP/TPP/TCP)-EGCG conjugates exhibited higher surface charge (-62.3 to -57.4 mV), smaller droplet sizes (0.96-1.44 μm), and lower flocculation indices (144-172%) than those stabilized by native proteins. These improvements contributed to significantly enhanced physical and oxidative stability. Among the conjugates, TSP-EGCG showed the best thermal stability, while TCP-EGCG exhibited the strongest emulsifying activity, possibly due to differences in 11S and 7S globulin content. Overall, the strategy of modifying legume proteins with EGCG through heat and pH treatments provides structure-function insights and offers a promising approach for enhancing the functional performance and extending the shelf life of walnut oil emulsions, supporting the development of sustainable functional foods based on alternative proteins.