Quality attributes of chicken breast proteins following sequential enzymatic hydrolysis and polyphenol conjugation

The present study evaluated the effects of sequential enzymatic hydrolysis and epigallocatechin gallate (EGCG) treatment on the physicochemical characteristics, techno-functional properties, antioxidant capacity, and in vitro digestibility of chicken breast proteins using a 2 × 2 factorial design consisting of intact protein (CB), EGCG-treated protein (CB-EGCG), hydrolyzed protein (CBH), and EGCG-treated hydrolyzed protein (CBH-EGCG). Chicken breast proteins were hydrolyzed using Alcalase (50 °C, 2 h), followed by EGCG treatment under alkaline conditions (pH 9.0, 24 h). Enzymatic hydrolysis increased sulfhydryl content and turbidity, whereas EGCG treatment reduced sulfhydryl content and further increased turbidity. FTIR spectra showed noticeable changes in the amide regions and phenolic-associated spectral regions following hydrolysis and EGCG treatment, particularly in CBH-EGCG. Bound polyphenol content was higher than free polyphenol content in both EGCG-treated groups and was significantly greater in CBH-EGCG than in CB-EGCG (P < 0.05). Water-holding capacity, oil absorption capacity, and emulsifying activity index increased following hydrolysis and EGCG treatment, whereas emulsion stability decreased after hydrolysis alone but improved following EGCG treatment. DPPH radical scavenging activity and ferric-reducing antioxidant power were significantly increased by both hydrolysis and EGCG treatment, with CBH-EGCG exhibiting the highest antioxidant activity (P < 0.05). In vitro digestibility increased following hydrolysis, whereas EGCG treatment reduced digestibility in intact proteins. However, CBH-EGCG maintained digestibility comparable to CBH. Overall, controlled enzymatic hydrolysis followed by EGCG treatment may provide a practical processing strategy for developing chicken breast protein ingredients with improved functional and antioxidant properties while maintaining desirable digestibility.