Optimization of Formulation and Evaluation of Iranian Yoghurt Drink (Doogh) Properties Fortified with Ziziphora L. clinopodiodes Essential Oil Microcapsules

The aim of this study was to compare the effect of Ziziphora L. clinopodiodes essential oil (ZEO) using whey protein isolate (WPI) and pectin microencapsulated on the physicochemical properties of Doogh. At the first step, the microcapsule concentration effect (0-0.03%) and storage time (1-21 days) on the properties of Doogh was evaluated, using the response surface methodology. pH increased and acidity decreased by increasing storage time but the effect of microcapsule concentration was not significant. The rate of serum phase separation in samples fortified with pectin microcapsules was lower than WPI. Antioxidant activity of Doogh samples containing pectin microcapsules was lower than WPI. At the second step, the optimized concentration of microcapsules (0.004 and 0.007% for WPI and pectin microcapsules, respectively) were added to Doogh samples and their sensorial and physical characteristics were compared. Sensorial scores of control sample were higher than WPI-ZEO and pectin-ZEO added sample. Particle size distribution and mean diameter of Doogh particles increased after addition of microcapsules but they had no significant effect on Zeta potential values.