Doogh (Yoghurt drink) is a traditional Iranian drink prepared through adding water and salt to yoghurt. Doogh‘s instability is a major problem which is the result of low pH (<4.00) and aggregation of casein. One solution is to employ hydrocolloids to improve the stability of the product. The aim of this study was to investigate the effect of psyllium husk gum on the stability and sensory properties of Doogh. Two different edible colors (β-lain and curcumin) were added to the product to enhance sensory properties. The hydrocolloid was also used at three concentrations (0.25, 0.75 and 1.25%). Serum separation, zeta potential, flow behavior, colorimetry and sensory properties were carried out. The results showed that as the concentration of hydrocolloid increases, instability in Doogh decreases and the most stable sample contained 1.25% hydrocolloid (the highest) and 5% color (the least). In the case of sensory analysis, hydrocolloid and color at the level of 1.25% and 10%, respectively, achieved the highest scores. Viscometry measurements showed that, Newtonian behavior of Doogh samples is not affected by hydrocolloid concentration. Finally, it was concluded that the best sample with highest scores was the one which containing 0.75% hydrocolloid and 10% for both edible colors.

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