Controlling the rheological properties of oil phases using controlled protein-polysaccharide aggregation and heteroaggregation in water-in-oil emulsions

In this study the influence of oppositely charged protein and polysaccharide microspheres on the rheological properties of single and mixed water-in-oil emulsions was investigated. Single and mixed aqueous phases of 40 wt % W/O emulsions were prepared by dispersing, under controlled conditions (pH 3.5, 100 mM NaCl), Whey Protein Isolate (WPI) and three different kinds of polysaccharides: High Methoxy Pectin (HMP), kappa Carrageenan (kC), and sodium alginate (SA). The oil phase consisted of 8 wt % Polyglycerol polyricinoleate (PGPR) in soybean oil . At pH 3.5, WPI carries positively charged groups, while polysaccharides have negatively charged groups. It was observed that before heating, single W/O emulsions had higher complex shear modulus and shear viscosity than mixed emulsions, which suggested stronger protein-polysaccharide interactions in single droplet systems. After subjecting to a thermal treatment (90 °C, 30 min), the rheological properties of the mixed emulsions were higher than for equivalent single emulsions, suggesting denser gel network formation between opposite charged emulsion droplets, especially in the WPI-HMP mixed system. The data from this study may be useful for development of reduced-fat margarine and spreads with low saturated and trans fat content.