The potential of Zataria multifliora and Mentha longifolia L. to improve the qualitative characteristics of probiotic yoghurt produced by cow - goat milk

Nowadays, due to some problems, such as allergic reactions and high fat content, the partial replacement of cow's milk with milk of other animals, such as goat's milk, is so crucial by proper techniques to improve the quality with the aim of yogurt production. The aim of this study was to evaluate the effect of Zataria multifliora and Mentha longifolia L extract on the qualitative characteristics of probiotic yogurt produced from the cow-goat milk in proportions 10: 90, 30: 70, 50: 50 and 0: 100. Sensory evaluation was performed on produced samples one day after production to selecting the best samples and then, the experiments were carried out on selected samples during 28 days. The results showed that, over time, acidity and syneresis values increased and pH value, viscosity and probiotic count decreased. The highest viscosity was related to the equal ratio of cow - goat milk and 0.05% of Zataria multifliora extract. The antioxidant activity (AA) trend was irregular but descending and extracts had a significant effect on AA. The treatment of cow-goat milk (10 : 90%) and 0.03% of Zataria multifliora extract had the highest probiotic count. The treatment of cow's milk (100%) containing the equal concentrations of two extract (0.02%), showed the highest color, taste, consistency and overall acceptance scores by panelist. As a conclusion, it can be concluded that in order to achieve the best quality of probiotic yogurt, various concentrations of extracts and optimal ratios of cow-goat milk should be used. .