Application of whey protein-polysaccharide complexes in aerated dairy gels

Abstract

Previous research has shown that heated soluble complexes of whey protein isolate (WPI) with polysaccharides can improve both foam stability and acid-induced gel strength. We utilized these complexes in aerated dairy gels, which could be formulated into novel-textured high-protein desserts. Two families of polysaccharides having different degrees of charge density were chosen. The first included: low methoxyl pectin (high charge), high methoxyl type D pectin (low charge), and guar gum (neutral charge). The second had three carrageenans, ??- (high charge), ??- (medium charge), and ??- (low charge). WPI-polysaccharide complexes were prepared by heating the mixed solutions (8% protein, 0 to 1% polysaccharide) at pH 7 and then mixing with heated skim milk powder (8% protein). To form aerated gels, 2% glucono-??-lactone (GDL) was added and foam was generated by whipping with a handheld frother. The foam set into a gel as the GDL acidified to a final pH of 4.2. The aerated gels were evaluated for stability, overrun, and rheological properties. Overall stability was indicated by measuring liquid separation drained from the foam before it set as a gel. Rheological results showed no significant difference in ix gelation time among samples; therefore, stronger interactions between WPI and high charge density polysaccharide were likely responsible for increased stability. In most cases overrun of aerated gels significantly decreased as polysaccharide concentration increased due to increased viscosity which limited air incorporation. However in some cases of high charge carrageenans, overrun increased as concentration increased, related to stronger interfacial films overcoming the effect of viscosity. Yield stress and G' are important rheological indicators of firmness and mouthfeel and are increased with increasing polysaccharide charge density. For both the pectin and carrageenan systems, it was found that yield stress and G' could be predicted using a multiple regression model using gel strength of no