Influence of γ-aminobutyric acid on gelling properties of heat-induced whey protein gels

gamma-Aminobutyric acid (GABA) is a non-protein amino acid that has attracted considerable attention due to its various health promoting benefits. Great efforts have been made to enrich GABA in food while few studies have considered that GABA may influence the protein functional properties, which are imperative to food quality. The present study investigated the effects of GABA on gelling properties of heat-induced whey protein gels at different pHs. GABA greatly strengthened the whey protein gels at pH 2.0 while weakened the gels at pH 6.5 and 8.0 (P < 0.05). At pH 2.0, GABA decreased protein leachability and enhanced water holding capacity (P < 0.05) by encouraging the disulfide cross-linking of alpha-lactalbumin and beta-lactoglobulin, which resulted in a well-structured gel network that can resist deformation and trap water. At pH 6.5, GABA increased the leach-out of beta-lactoglobulin which explained the reduced gel hardness and improved gel swelling ratio (P < 0.05). At pH 8.0, GABA treatment resulted in a less cohesive gel despite a decreased protein leachability (P < 0.05) and an increased incorporation of alpha-lactalbumin, beta-lactoglobulin, and BSA into the gel network. In summary, the presence of GABA exhibited a pH-dependent impact on the gelling properties of heat-induced whey protein gels.