The influence of Basil seed gum concentration on the stability, particle size and rheological properties of oil-in- water emulsion stabilized by whey protein isolate

In this study the effect of Basil seed gum (BSG) concentration (0%, 0.005%, 0.02%, 0.08%, 0.15% and 0.3% w/w) on the stability, particle size distribution and rheological properties of O/W emulsion stabilized by whey protein isolate (0.5% w/w) was investigated at neutral pH. The emulsion prepared by using a sonicator with a nominal power output of 150 W and an operating frequency of 20 kHz. Sonication of samples was carried out in a temperature-controlled chamber at a constant temperature of 20 ºC for 6minutes. The results of stability showed that after 28 days the highest and the lowest creaming index was related to the emulsion with 0.3% and 0.15% Basil seed gum (w/w), respectively. Rheological data showed that all model emulsions exhibit non-Newtonian shear–thinning flow behaviors (n<1). The best model for emulsions without and with 0.005% Basil seed gum (w/w) was Ostwald and for the another emulsions was Herschel–Balklley. The consistency coefficient k, which is a reflection of the viscosity, has been significantly increased with the increasing gum concentration. The flow behavior index n, which indicates the extend of shea-thining behavior is decreased by the increase in Basil seed gum concentration. The results of frequency sweep experiments showed that at low frequency, all emulsions indicated both viscous(G'') and elastic (G') behavior but at high frequency all emulsions only indicated a viscous behavior The results of particle size distribution showed that the addition of Basil seed gum up to 0.3% had no significant effect on the particle size. At 0.3% concentration, over presence non adsorbed polysacharid result in depletion fluccolation and significant increase in particle size