Emulsifying properties of ovalbumin in mixtures with sulphated polysaccharides: effects of pH, ionic strength, heat and high-pressure treatment

The influence of sulphated polysaccharides (dextran sulphate (DS), i-cafiag eenan (i-CAR) and kappa-carrageenan (kappa-CAR)) on the emulsifying propert ies of ovalbumin (OVA) has been investigated over a range of pressures and temperatures. Oil-in-water emulsions (10gl(-1) protein, 200ml(-1) n-tetrade cane, pH 6.2) prepared with heat-treated (80 degrees C for 10min) mixtures of OVA + DS (1:0.25 by weight) had increased creaming stability but unchang ed average droplet size compared to those made with untreated OVA and OVA DS. Emulsions made with pressure-processed (600MPa for 20min) OVA + DS (1: 0.25 or 1:0.5 by weight) mixtures had the best emulsifying efficiency and s tability. Under similar experimental conditions, replacement of DS with eit her i- or kappa-CAR gave emulsions with larger droplets and more rapid seru m separation, probably owing to depletion flocculation. High-pressure treat ment (600 MPa) of the OVA and mixed biopolymer solutions at pH 6.2 in the p resence of salt (>0.04M) led to unstable emulsions, and so the protective e ffect of DS was lost. High-pressure treatment (600MPa) of emulsions prepare d with native OVA or OVA + DS mixtures induced significant levels of floccu lation, as indicated by changes in the average droplet size and creaming be haviour. (C) 2000 Society of Chemical Industry.