Some physicochemical, rheological, antioxidant, microbiological and sensory properties of kefirs with propolis at different ratios

In this study, kefir samples containing 5% (w/v) sugar, 0.15% (v/v) strawberry flavor and propolis extract at different ratios [0.150, 0.225 and 0.300% (v/v)] were produced, and they were stored in a refrigerator at 4±1°C for 8 days. Some physicochemical, antioxidant, rheological, microbiological and sensory properties of kefir samples were determined on the 1st, 4th and 8th days of storage. The addition of propolis extract and storage had no effect on dry matter, protein, fat contents, L* and a* values, rheological properties (apparent viscosity, consistency coefficient and flow behavior index) and total lactobacilli, lactococci and yeast numbers of kefir samples (p>0.05). The addition of propolis extract did not influence the pH and acidity (lactic acid) values of kefir samples (p>0.05) but the pH values of samples decreased (p<0.05) while acidity values increased during storage (p<0.05). Addition of propolis extract to kefir drinks increased the b* (yellowness) values of samples (p<0.05). All kefir samples showed pseudoplastic flow behavior. It was determined that the total antioxidant capacity and phenolic content of samples increased by an increase in the ratio of propolis extract added to kefir samples, and these values decreased during storage. It was found that the addition of propolis extract did not affect the sensory color and taste scores of kefir samples adversely. Kefir samples containing 0.225% and 0.300% propolis extract received sensory scores similar to the control group in terms of odor, and the overall liking scores of kefir samples were similar to those of control group for kefir drinks containing 0.150 and 0.225% propolis extract. Results indicated that it was possible to produce kefir drinks with 0.225% propolis extract, which was acceptable in terms of both sensory and increased functional properties, and that this product could be stored up to 8 days.