Impact of Covalent Binding with p-Coumaric Acid on Pea Protein's Structural and Functional Properties

This study investigated the effects of covalent bonding between pea protein isolate (PPI) and p-coumaric acid (p-CA) on the protein's secondary structure, solubility, foaming properties, emulsifying capacity, and thermal stability. Binding p-CA led to alterations in the secondary structure of PPI, including an increase in α-helix and random coil and a decrease in β-turn. Additionally, it resulted in a reduction in SH and NH groups, as well as a decrease in particle size. As the amount of bound p-CA increased, an increased tendency for aggregation was proposed, resulting in the formation of soluble aggregates through hydrophobic interactions, which was confirmed by a reduction in particle size of proteins after being dissolved in SDS. These structural modifications influenced the protein's functional properties, with the conjugates showing enhanced solubility and emulsifying capacity across various pH levels, but weaker foaming capacity and foam stability. Furthermore, the conjugates exhibited a lower initial denaturation temperature but a higher thermal denaturation enthalpy change (ΔH) compared to PPI, which may be attributed to protein unfolding and the formation of new covalent bonds. This study highlights the potential of p-CA covalent modification of PPI to enhance its functional properties, making it more suitable for food industry applications.