Effect of pH and mixing ratios on the synergistic enhancement of Bambara groundnut-whey protein gels

Plant and animal-based protein mixtures are increasingly recognised as a new group of functional ingredients offering novel structuring capabilities. When combining new sources of plant and animal proteins, it is important to gain a mechanistic understanding of such mixtures to enable their use as food ingredients. In this study, we have investigated the synergistic enhancement of Bambara groundnut (Vigna subterranea (L.) Verdc.) protein isolates [BGN-PI] when combined with whey protein isolates [WPI] in heat-induced gelled mixtures. Mixed proteins were characterised for their rheological and structural properties at 12% (w/w) total protein concentrations at three mixing ratios (70:30, 50:50 and 30:70) and three pH values (pH 3, 5 and 7), with comparison to the single protein systems. At acidic pH (pH 3) WPI dominated the gel formation of the mixed gels with BGN-PI having no effect, whilst close to the isoelectric point of both proteins at pH 5, BGN-PI lowered the gel strength of the mixtures. Synergistic enhancement was observed at pH 7, where independent of the BGN-PI concentration in the mixtures, the mixed gels were characterised with similar high gel strengths comparable to that of the single BGN-PI. Hence, BGN-PI dominated the elasticity of the mixed gel networks at neutral pH.