Effect of high acyl gellan gum and pH on the structural and foaming properties of heated whey protein suspensions

Effects of association between high-acyl gellan gum and whey protein on heat-induced aggregation and foaming properties of aggregates were assessed in aqueous suspensions. Associative complexes were identified by turbidity and colloidal charge below pH 6, and a balance of charge in the complexes was achieved at pH 5 with a 5:1 protein:polysaccharide ratio. As gellan gum content increased, size of aggregates formed by heating at pH 5 decreased (>1000 nm to 200-300 nm). Microscopy showed polysaccharide chains adhered to spherical aggregates at pH 5 and 6. Gellan gum added to protein before heating did not increase foam volume yet doubled foam half-life at pH 5 when used at a 2:1 protein-to-polysaccharide ratio. Microscopy showed that protein aggregates with attached gellan gum were present in drained foams. These findings indicate that gellan gum improves foam stability of heated whey protein at pH 5 by reducing aggregate size and adhering to aggregates.