Effect of propolis extract addition on some physicochemical, microbiological, and sensory properties of kefir drinks

Kefir drinks with sugar (5%, w/v), strawberry flavor (0.15%, v/v), and propolis extract (PE) at different ratios (0.150%, 0.225%, and 0.300%, v/v) were produced and stored at 4°C, and their physicochemical, rheological, microbiological, and sensory properties were monitored during storage. The ratio of PE and storage time had an insignificant effect on the dry matter, protein, fat contents, Commission Internationale de l'Eclairage (CIE) L* and a* color values, apparent viscosity, consistency coefficient, flow behavior index, Lactobacillus spp., Lactococcus spp., and yeast counts of kefir drinks (p > .05). The CIE b* values of kefir drinks increased with an increase in PE ratio (p < .05). All kefir samples exhibited a pseudoplastic flow behavior. Initially, the total antioxidant capacity of kefir drinks was 2.19 μmol TE/100 mL, which increased to 2.51 μmol TE/100 mL for kefir drinks with 0.225% PE. The total phenolic content and antioxidant capacity of kefir drinks with PE decreased during storage. PE addition did not influence the sensory color and taste liking scores of kefir drinks adversely until the 8th day of storage. In terms of odor liking scores, kefir drinks with 0.225% and 0.300% PE had a similar score to control drinks. Additionally, kefir drinks with 0.150% and 0.225% PE received an overall liking score similar to control drinks. Results indicated that the incorporation of PE at a ratio of 0.225% was recommended for the production of strawberry-flavored kefir drinks with acceptable sensory characteristics and increased functional properties, and this product could be stored for up to 8 days.