Utilizing Whey Protein Isolate and Polysaccharide Complexes to Stabilize Aerated Dairy Gels

Abstract Text: 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. The objective of this study is to determine the effect of polysaccharide charge density and concentration within a WPI-polysaccharide complex on the properties of aerated gels. Three polysaccharides having different degrees of charge density were chosen: low methoxyl pectin (LM-12), high methoxyl type D pectin (HM-D), and guar gum. WPI-polysaccharide complexes were prepared by heating the mixed solutions (8% protein, 0 to 1% polysaccharide) at pH 7. To form aerated gels, 2% glucono-δ-lactone (GDL) was added to the solutions 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 overrun and rheological properties. Stability was determined by measuring drainage (the volume of liquid separated from the aerated gels).

Overrun of aerated gel (179% to 14%) significantly decreased as polysaccharide concentration increased due to increased viscosity which limited air incorporation. Increased concentration was significantly related to increased stability (P < 0.001) which could be due to increased viscosity of the pre-foam solutions limiting the mobility of the air bubbles. A negative logarithmic relationship was found between solution viscosity and drainage. However, charge density played an important role on stability. Plot of drainage against solution viscosity revealed that drainage was lowest in samples with high charge density pectin (LM-12) followed by those with low charge density pectin (HM-D). Aerated gels with guar gum (no charge) did not show improvement to stability as separation still occurred even at highest guar concentration. Rheological results showed no significant difference in gelation time among samples; therefore, stronger interactions between WPI and high charge density polysaccharide were likely responsible for increased stability. Rheological results also revealed that aerated gels with LM-12 pectin had the highest final elastic modulus, followed by guar gum, then HM pectin gels.

Stable dairy aerated gels can be created from WPI-polysaccharide complexes. High charge density polysaccharides, at concentrations that provide adequate viscosity, are needed to achieve stability while also maintaining solution overrun capabilities. This can inform the formulation of dairy-based gels set by acid or calcium such as whipped yogurts and mousses.

Keywords: acid-induced gelation, aeration, whey protein