The effect of psyllium husk and edible colorants (betalain & curcumin) on the stability, physical and sensory properties of Iranian traditional drink (doogh)

Doogh is a traditional Iranian drink prepared by adding water and salt to yoghurt and sometimes flavoring. Instability a major problem which is the result of low pH (<4.00) and aggregation of caseins. The aim of this project is to distinguish the effect of psyllium husk hydrocolloid on the stability and sensory properties of Doogh. In addition, two different edible color added to the product to enhance sensory properties by vision attraction. Hydrocolloid added in three concentration (0.25, 0.75 and 1.25%) and edible colors (β-lain and curcumin) were used for 5, 10 and 15% in samples. Serum separation, zeta potential, flow behavior, Colorimetry and sensory properties was measured during this research. Results obtain that as the concentration of hydrocolloid increase, instability in Doogh decrease and the most stable sample contains 1.25% hydrocolloid (the highest) and 5% color (the least), measurements of zeta potential also showed the same results. In sensory analysis, hydrocolloid and color at the level of 1.25% and 10%, respectively, achieve the highest scores.  Viscometry measurements showed that, Newtonian behavior of Doogh samples isnchr(chr('39')39chr('39'))t affected by hydrocolloid concentration. Finally, we conclude that the best sample, that shows the best results in all measurements, contains 0.75% hydrocolloid and 10% for both edible colors.