A Study into the Effects of Chosen Lactic Acid Bacteria Cultures on the Quality Characteristics of Fermented Dairy, Dairy–Oat, and Oat Beverages

The growing demand for plant-based and hybrid dairy–plant beverages has driven interest in optimizing their fermentation processes. This study investigates the effects of selected lactic acid bacteria (LAB) cultures on the quality characteristics of fermented dairy, dairy–oat, and oat beverages. The term ‘dairy-oat beverage’ refers to a hybrid product composed of cow’s milk and an oat-based drink in a 1:1 ratio. Cow’s milk, an oat beverage, and a 1:1 mixture of both were inoculated with traditional yogurt cultures (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and/or probiotic strains (Lactiplantibacillus plantarum 299v and Lactobacillus acidophilus La-5). Fermentation was conducted for 6 h at 37 °C, followed by 28 days of cold storage. pH, texture (hardness and adhesiveness), syneresis, carbohydrate content, and bacterial viability were assessed. The selection of lactic acid bacteria cultures had a significant impact on the quality attributes of the beverages. Both the bacterial culture type and the base material played a crucial role in determining the beverages’ texture, stability, and overall quality. Mixed bacterial cultures exhibited higher hardness, while milk and dairy–oat samples fermented with the yogurt culture demonstrated better structural stability. Fermentation influenced sugar levels, and bacterial viability depended on the beverage type and storage conditions. The selection of lactic acid bacteria cultures significantly impacts the quality of fermented beverages. Further optimization of bacterial culture combinations could improve these products’ stability and sensory properties.