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

Abstract

Mixtures of denatured soy whey proteins (dSWP) and soluble soybean polysaccharides (SSPS) were used to stabilize 5wt.% 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 2.5wt.% biopolymer in the aqueous phase), emulsions did not phase separate for >60days at pH3 and 21days at pH8. Irrespective of the protein–polysaccharide ratio, emulsions prepared at lower pH (3–4) showed better long-term stability versus pH5–8. The negligible surface charge (−2mV) at low pH suggested the presence of dSWP–SSPS complexes that promoted emulsion stability via steric hindrance. The higher surface charge at pH7–8 (near −20mV) prevented mixed dSWP–SSPS layer formation around the dispersed oil droplets resulting in limited emulsion stability. A deleterious effect of 1M 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.