Exogenous Polyphenols Inhibited Flavor Degradation in Legume Protein Matrices

Abstract

Significant off-flavors associated with protein-rich plant ingredients have hindered their consumer acceptance, thus limiting their market share. Off-flavors like “beany” and “grassy” are products of Maillard reactions and lipid oxidation that can occur during processing and storage. Polyphenols, known for their protein-binding capabilities and inherent antioxidant properties, have emerged as a potential solution to disrupt these reactions. Larger polyphenol structures with more hydroxyl groups have a greater ability to bind proteins, potentially leading to more significant off-flavor reduction as compared to smaller polyphenols. Therefore, it was hypothesized that polymeric polyphenols would reduce off-flavors in pea and soy protein solutions more effectively than monomeric polyphenols. Aqueous pea (10% w/v) and soy (8% w/v) protein solutions were treated with 0.02% w/w catechin (CAT), green tea extract (GTE), grape seed extract (GSE), or tannic acid (TA). The quantification of free polyphenols showed that at least 52% of all tested polyphenols were bound to proteins (GSE > TA > GTE > CAT). Purified polyphenols (CAT and TA) showed a higher affinity for α-dicarbonyl trapping than crude extracts (GSE and GTE). Polyphenol addition significantly reduced 2-furanpentyl and benzaldehyde production in protein solutions. High molecular weight (MW) polyphenols (GSE and TA) were able to inhibit these pathways through protein–polyphenol binding, which likely prevented amine groups from reacting with reducing sugars. Low MW polyphenols had alternative inhibition capabilities, including lysine binding and trapping of α-dicarbonyls. Results indicate that the addition of polyphenols disrupted flavor degradation pathways and limited the production of their products.