Stabilization of oil-in-water emulsions using mixtures of denatured soy whey proteins and soluble soybean polysaccharides

Mixtures of denatured soy whey proteins (dSWP) and soluble soybean polysaccharides (SSPS) were used to stabilize 5 wt.% oil-in-water (O/W) emulsions against coalescence and phase separation. Emulsions prepared with either dSWP or SSPS at low concentrations demonstrated limited stability. At an optimal SSPS:dSWP ratio of 1.5:1.0 (corresponding to 2.5 wt.% biopolymer in the aqueous phase), emulsions did not phase separate for >60 days at pH 3 and 21 days at pH 8. Irrespective of the protein-polysaccharide ratio, emulsions prepared at lower pH (3-4) showed better long-term stability versus pH 5-8. The negligible surface charge (-2 mV) at low pH suggested the presence of dSWP-SSPS complexes that promoted emulsion stability via steric hindrance. The higher surface charge at pH 7-8 (near 20 mV) prevented mixed dSWP-SSPS layer formation around the dispersed oil droplets resulting in limited emulsion stability. A deleterious effect of 1 M NaCl on emulsion stability was noted, further confirming mixed dSWP-SSPS layer formation as the dominant mode of stabilization. Overall, this study showed that the presence of dSWP-SSPS interfacial layers promoted the capacity of O/W emulsions to resist oil droplet coalescence and phase separation. (C) 2013 Elsevier Ltd. All rights reserved.