Investigating the effect of dill and garlic extracts on shelf-life and sensory properties of heat treated non-carbonated doogh

Doogh is a fermented dairy beverage which its shelf-life can be reduced by the activity of microorganisms and chemical and sensory changes of product. This study aimed at producing a heat treated doogh using combination of dill (0.05, 0.075, and 0.1%) and garlic (0.04, 0.06, and 0.08%) extracts as biopreservatives. Microbial, chemical, and sensory properties of samples were evaluated during six weeks of storage at 8°C. The results showed that microbial count were dependent on the amounts of extracts used in doogh samples formulation. On the other hand, by increasing concentration of extracts, total bacterial counts, mold and yeast counts decreased significantly (p<0.05). Also, the results showed that amounts of pH decreased and acidity increased significantly in doogh samples over time, but these indices have less changed in treatments containing different concentrations of dill and garlic extracts compared to control sample (p<0.05). Also, results revealed that increasing the extract concentrations increased scores of most sensory parameter (flavor, odor, mouthfeel, and overall acceptability) (p<0.05). Control sample had mostly the least scores of sensory properties (except color) and the highest microbial load and acidity during storage time which had significant difference with the most treatments (p<0.05). According to the results obtained, the doogh sample containing 0.1% of dill extract and 0.08% of garlic extract was considered to be the best treatment.