Determination of physiochemical, sensory and microbiological properties of water kefir produced from dried persimmon, carob and oleaster

Water kefir is a fermented beverage made by adding water kefir grains to a mixture of water, fruit, and sugar. With the increase in consumption and interest in functional foods, water kefir has started to find itself more and more among beverages. The number of studies on water kefir has increased rapidly in recent years. Water kefir is obtained by fermenting water kefir grains with suitable substrates under appropriate conditions and filtering. Lactic acid fermentation takes place in water kefir where lactic acid bacteria are dominant. There are compounds that must be present in the substrate. These are water and polysaccharides. Many different foodstuffs can be used as a source of polysaccharides. In addition to these basic components, various fruits are added to the substrate to be a nitrogen source, to give aroma and to increase its functional properties. The main microorganisms found in water kefir are lactic acid bacteria, yeasts, bifidobacteria and acetic acid bacteria. However, water kefir grain composition can consist of quite different types and species of microorganisms, depending on the geography where it is produced. But the dominant species is mostly lactic acid bacteria. In this study, 18 different water kefirs were produced by using dried persimmon, carob and oleaster fruits, honey, sugar and water at pH values of 6.5–7.5–8.5. Microbiological, bioavailability, physicochemical and sensory properties of these kefirs were investigated. For microbiological and physicochemical research; Total yeast, total lactic acid bacteria, total acetic acid bacteria, kefir grain mass (dry and wet), pH values for 1 month after production, total dry matter, water soluble dry matter, electrical conductivity, titration acidity analyzes were made. For the examination of bioavailability properties; antioxidant capacity, total phenolic and flavonoid compounds, and in-vitro bioavailability were measured. Total antioxidant capacity, total phenolic and total flavonoid compounds were determined by spectrophotometric methods, and in-vitro bioavailability was determined by mouth, stomach and intestine simulation method. Sensory examinations were carried out with sensory tests performed daily for a period of 1 month. In the studies, the number of lactic acid bacteria was found to be higher in carob water kefir than in other samples. In addition, the high pre- and post-digestion antioxidant capacity, TPC values and TFC retention rates, high wet and dry grain increase in carob water kefir were evaluated as an indicator of the potential to be a strong probiotic and functional beverage. The biggest difference of carob from persimmon and oleaster fruits is its high calcium content. Considering the effect of calcium on water kefir grains in many studies on water kefir, it has been evaluated that the high increase in kefir grain weight in carob water kefir supports the positive effect of calcium on water kefir fermentation. It has been evaluated that water kefir with persimmons can be a preferred water kefir beverage with high sensory scores and cultural count results, pre- and post-digestion antioxidant capacity, TPC and TFC analysis results. Studies; The pH value of 8.5 suppresses the growth of LAB, AAB, and yeast, the LAB number is higher in the samples established with water at pH 7.5 in all kefir varieties, the water with a pH value of 7.5 will create a better environment for water kefir production, Honey has a significant positive effect on the bioavailability of pre- and post-digestion analyzes as well as providing important and intriguing results for further research.