Determination of quality parameters of kefir produced with pollen extract during the storage period

Changes in modern lifestyle and dietary habits negatively affect human health. Therefore, the importance of functional foods containing probiotics and bioactive substances is increasing. Bee pollen, a product produced by bees from plant pollen used as a dietary supplement, is high in bioactive compounds. In this context, in the current study, four different kefir samples were prepared with 0.25% (K-025), 0.5% (K-05), and 1% (K-1) concentrations of bee pollen extract to obtain kefir with high bioactive substance content and without bee pollen (Control). The samples were stored at 4°C for 21 days. First, the botanical source of the bee pollen to be added to the kefir samples was determined. During the storage period of the kefir samples on the 1st, 7th, 14th, and 21st days, their physicochemical (total dry matter, ash, protein, fat, titratable acidity, pH, color) and sensory properties were evaluated, total phenolic content, antioxidant activity (DPPH• (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power)) were determined, and phenolic compound content was determined by liquid chromatography-high resolution mass spectrometry (LC-HR MS). At the same time, total mesophilic aerobic bacteria, lactobacilli, lactococcus, yeast and mold, and acetic acid bacteria counts were performed to evaluate the effect of bee pollen on the microbial content of kefir samples. As a result of microscopic analyses, it was determined that the bee pollen added to kefir was bifloral (Verbascum sp. and Hypericum sp.). The addition of bee pollen to kefir improved its physicochemical properties. According to sensory analysis, the K-0.25 sample was the most preferred kefir. The total phenolic content, DPPH, and FRAP antioxidant activity values of bee pollen-added kefirs ranged from 62.58±2.5 (Control, 21st day) to 123.25±7.2 (K-1, 7th day) µg GAE/mg, 23.65±1.6 (Control, 1st day) to 78.54±0.8 (K-1, 7th day) µgTE/g, and 31.01±3.1 (Control, 1st day) to 106.80±2.8 (K-1, 7th day) µgTE/g, respectively. The phenolic compounds detected at the highest levels were benzoic acid, luteolin, and eriodictyol. Addition of bee pollen improved the bioactive substance content and microbiological properties of kefir samples until the 7th day of storage.