# The Effect of Varying Out Beverage Ratios on the Characteristics of Fermented Dairy-Oat Beverages
## 4 Discussion  
The results of this study highlight the significant impact of varying oat beverage proportions on the physicochemical, textural, sensory, and microbiological properties of fermented dairy-oat beverages. The observed changes in fermentation kinetics, pH stability, syneresis, and microbial viability indicate that the interaction between dairy proteins and oat components plays a crucial role in determining the final product characteristics. In summary, the content of basic nutrients in dairy-oat beverages changes with an increasing proportion of oat beverage. The introduction of oat beverage to cow's milk leads to a decrease in protein, fat, and lactose content, while simultaneously increasing the overall carbohydrate content [1,2]. These findings are consistent with previous studies, which have also demonstrated that plant-based ingredients influence the physicochemical properties and fermentation dynamics of dairy alternatives [1,3]. Changes in the chemical composition of dairy-oat beverages have significant consequences for fermentation and the quality of the final product [12]. Various studies highlight how specific components, such as soluble fibers and probiotic cultures, enhance both the nutritional profile and sensory attributes of these beverages [3, 4, 5]. In particular, the presence of oat-derived beta-glucans and fibers may contribute to changes in viscosity and gel structure, as previously reported in studies on plant-based fermented products [4,5]. An increased proportion of oat beverage may result in a longer fermentation time, a milder flavor, a more fluid consistency, and a greater tendency towards syneresis [13]. Milk protein, especially casein, plays a crucial role in forming the gel structure during fermentation [14,15]. A smaller amount of protein in beverages with a higher oat beverage addition can lead to a weaker protein network, which will affect the consistency and texture of the final product [16,17]. Similar observations were made in oat-based probiotic drinks, where protein interactions influenced the microstructure and texture of the final product [7]. Lactose is the primary substrate for lactic acid bacteria (_Lactobacillus, Streptococcus_). A smaller amount of lactose in beverages with a higher oat beverage content may slow down fermentation, extending the acidification time and changing the acid profile [13]. This can result in a higher pH and milder flavor compared to classic dairy yogurt [5]. On the other hand, oat beverage provides additional sugars, mainly starch and \(\beta\)-glucans [18]. Starch can be hydrolyzed into simple sugars, which can be utilized by some bacterial strains, affecting the fermentation profile and extending the adaptation period of the microflora [19,20]. Studies on oat and buckwheat fermentation support this finding, indicating that starch hydrolysis contributes to alternative metabolic pathways for microbial growth [7]. In our study, the fermentation was most vigorous in beverages containing 0-50% oats, suggesting that this oat content is optimal for maintaining the activity of fermenting bacteria. For individuals with lactose intolerance, fermented beverages with \(>\)75% oats could be a good alternative, as they contain very low levels of lactose after just a few hours of fermentation [21,22]. Further research is needed to fully understand the implications of oat-based products on diverse dietary needs. Additionally, investigating the enzymatic hydrolysis of oat starch may help optimize the fermentation process and enhance the bioavailability of key nutrients, as suggested in studies on enzyme-modified oat formulations [23]. Oat beverage slows down lactose breakdown, suggesting that in prod ucts with a high oat content, the addition of lactase enzymes could be considered to further reduce lactose levels [13; 23]. Further research is warranted into the effects of adding enzymes (e.g., lactase, amylase) on improving fermentation and reducing lactose in dairy-oat beverages.