Enhancing the functional properties of peanut protein hydrolysates: covalent modification with chlorogenic acid

Abstract

SummaryThis study aimed to enhance the functional properties of peanut protein hydrolysates (PPHs) by coupling limited enzymatic hydrolysis with chlorogenic acid (CGA) modification, thus offering novel insights into the potential food industry applications of peanut proteins. Initially, peanut protein isolate was hydrolysed using trypsin. Subsequently, covalent conjugation with CGA was achieved via free‐radical grafting. The moderately hydrolysed 4% PPHs had the highest polyphenol‐binding capacity. Measurement of the PPHs‐CGA complex revealed that free amino, thiol, and tryptophan contents were reduced. The amino acid content results also showed that cysteine, lysine, arginine, and methionine (with amino or thiol groups) were the primary binding sites. Spherical or rod‐like structures were observed in the scanning electron microscopy images of PPHs‐CGA, and its particle size was larger than that of the PPHs. After combining PPHs and CGA, the fluorescence intensity decreased, Fourier‐transform infrared spectrum showed a shift in the absorption peak, and electrophoresis band weakened, indicating that covalent binding was successful. PPHs with different degrees of hydrolysis have different levels of exposure to amino acids, and their antioxidant properties differ when combined with CGA. After combining, the surface hydrophobicity was reduced, and the secondary structure was unfolded and extended, thereby improving its emulsifying properties. In summary, PPHs‐CGA may be used in the food industry as a bi‐type food factor and proposes a new application for peanut protein in food.