Effect of Guar Gum on Texture and Volatility of Essential Oils in Iranian Drinking Yogurt (doogh)

Dairy beverages have low pH and after period of time casein curb separated from serum. In this research, Guar gum was added at 0.08, 0.1, 0.15 and 0.2% to prevent serum separation and thus reducing volatility of essential oils. In order to investigate the effect of different levels of added hydrocolloid, the quantity of serum separation, pH and organoleptic were evaluated weekly for a month. The rheological properties of the sample were also measured a week after production. The obtained results demonstrated that adding hydrocolloid reduces the volatility of added essential oils due to its effect on viscosity and Prevention on serum separation. For that reason, generally, appraiser group preferred treatments containing.10 and.15 of hydrocolloid to control the sample.The investigation of rheological properties also demonstrated that the viscosity of all treatments reduces with increase in shear rate.