Enhancing zein functionality through sequential limited Alcalase hydrolysis and transglutaminase treatment: Structural changes and functional properties

This study investigated the effects of sequential enzymatic hydrolysis using Alcalase, followed by transglutaminase conjugation on the secondary and tertiary structures, hydrophobicity, free amine content, protein-protein interactions, and functional properties of zein. Fourier-transform infrared spectroscopy showed that the most significant secondary structural changes, characterized by a decrease in α-helix content and an increase in β-turns, occurred at a higher degree of hydrolysis. At a 2 % degree of hydrolysis, it revealed notable emulsifying activity (65.96 m²/g), while at 5 % hydrolysis, it achieved the highest solubility (75.06 %). Additionally, the zein hydrolysate with a 7 % hydrolysis degree, treated with transglutaminase, demonstrated improved H₀ values (2992.33), enhanced foam capacity (65.95 %), and increased solubilized protein content in a dithiothreitol extractant (31.35 %). Meanwhile, native zein treated with transglutaminase showed the highest water holding capacity (4.47 g/g). Overall, the combined enzymatic approach modified zein structure and properties, suggesting potential for improving functionality in plant-based food applications.