Effects of stabilizer mixture on physical stability of non-fat Doogh, an Iranian traditional drink.

Introduction: Doogh is a traditional beverage and separation of serum during storage is a major problem in this product which happens due to low pH and aggregation of caseins. The aim of this study was to evaluate the effect of adding carboxy methyl cellulose, Persian and locust bean gum individually and in combination on doogh stabilization during storage time. Materials and Methods: Doogh samples were prepared from the reconstruction of skim milk powder. Then, hydrocolloid solutions (0.15% locust bean, 0.6% carboxy methyl cellulose, 0.1% locust bean: 0.2% carboxy methyl cellulose and 0.1% locust bean: 0.1% Persian) were added to them and were kept in 5°C storage temperature for 28 days. The measurement of serum separation during storage time (28 days), particle size distribution and rheological tests were performed at baseline and the end of study. Finally, sensory attributes of treatments were determined with 30 panelists. Results: Adding carboxy methyl cellulose and locust bean gums individually resulted in increasing the stability of Doogh, but lower levels of locust bean showed a better impact on Doogh’s stability. However, the mixture of locust bean: carboxy methyl cellulose indicated the highest stability during storage and had the smallest particle size because of reduced accumulation of casein micelles. Adding hydrocolloids resulted in changing rheological behavior of Doogh from Newtonian to pseudoplastic. Moreover, the sensory panelists ascribed the highest score to the samples prepared by 0.1% locust bean: 0.2% carboxy methyl cellulose. Conclusion: Combination of absorbent (carboxy methyl cellulose or Persian gum) and non-absorbent (locust bean) hydrocolloids, through three mechanisms including, spatial inhibition, electrostatic repulsion and increasing viscosity of the continuous phase led to a significant increase in stability of non-fat Doogh. It is worth mentioning that combination of locust bean and Persian hydrocolloids were stable, but in respect of sensory evaluation, the aforementioned combination received a lower score than the mixture of locust bean and carboxy methyl cellulose. Keywords: Beverages, Carboxymethylcellulose Sodium, Colloids, Dairy Products, Food Preservatives