Examination of physicochemical and microbiological properties of plant- and animal-based probiotic yogurts fermented by adding buckwheat

In recent years, both the fermentation of probiotic yogurts with prebiotic effective pseudocereals and the production of plant-based probiotic yogurts are among the considerable research topics. In this field, studies with buckwheat and almond-based beverages fermentation are limited. This study was aimed at the examination of pH, acidity, textural, rheological, microbiological properties, and metabolomics results on final products produced by fermentation with buckwheat or inulin and vegan probiotic culture (Danisco ® Vege 022) using cow's milk and almond-based beverages. Fermented products were produced with the addition of 0%, 2.5%, 5%, and 7.5% inulin or buckwheat, and pH, acidity, microbiological, texture, and rheology analyses were performed on the 1st, 14th, and 28th days of storage. As a result of these analyses, the metabolite profiles of the products with the closest acceptability to traditional yogurt were analyzed. In this study, there has been statistically significant differences between the pH and titratable acidity of all samples at different storage times (p<0,05). The addition of buckwheat to cow's milk, and the addition of inulin to almond-based beverage has prevented post-acidification. Microbiological analysis has shown that there were statistically significant differences between the lactic acid bacteria counts of all samples. (p<0,001). Among cow's milk samples, the highest count of Streptococcus thermophillus, Lactobacillus bulgaricus, Lactobacillus acidophillus, and Bifidobacterium animalis are in the product fermented with 5% buckwheat at the end of the storage. Almond-based beverages with 7.5% buckwheat S.thermophillus count was higher than other almond-based samples at the end of storage (p<0,05). Furthermore, all cow's milk samples' total number of starter cultures (>1x10 7 cfu/ml) that should be present at the time of consumption during the 28-day storage period were above the lower limits specified in the Turkish Food Codex Fermented Dairy Products Communiqué. All samples' rheological properties have been found frequency dependency. As the amount of buckwheat added to cow's milk and almond-based beverages increased, the complex modulus (G*) value increased during the storage. All samples were correlated with Cross and Moore models of non-Newtonian flow models. The addition of buckwheat to cow's milk and almond-based beverages increased firmness, consistency, and index of viscosity were increased. Among the cow's milk samples, the textural property of product with 2.5% buckwheat added was the weakest. Almond-based products fermented with 0%, 2.5%, 5% inulin, and 2.5% buckwheat were observed to have weak coagulum.Metabolite characterization has changed with the addition of inulin or buckwheat during storage. In conclusion, buckwheat or inulin addition to animal-based milk and plant-based beverages is an effective way to improve yogurts' probiotic activity, textural, rheological properties, and metabolite profile. Nevertheless, to enhance the samples' acceptability for consumers and understand the health effects, further studies are needed.