Production of Lactic Acid Wort-Based Beverages with Rosehip, Lemongrass, and Eucalyptus Oils

Rosehip, lemongrass, and eucalyptus oil was studied for the first time as a strategy for improvement of lactic acid wort-based beverage characteristics. Each oil was added to wort at doses of 0.01%, 0.02%, and 0.03% (v/v) by vigorous shaking to ensure homogenous distribution, and fermentation was carried out with Lacticaseibacillus casei spp. rhamnosus Oly at 25 ± 1 °C for 48 h. Oil addition influenced microbial growth, phenolic composition, antioxidant activity, and sensory quality. Although higher oil concentrations reduced lactic acid bacteria viability, in all the beverages the concentration of viable lactic acid bacteria cells was above 107 CFU/mL. Total phenolic content and phenolic acids increased after fermentation, although flavonoid levels were largely unaffected. Antioxidant activity showed assay-dependent trends, with decreases observed in ABTS measurements during lactic acid fermentation, whereas CUPRAC values remained stable or slightly improved. Sensory evaluation revealed that all the beverages with eucalyptus oil received lower scores than the control sample. Rosehip oil enhanced flavor only at a concentration of 0.03%, while lemongrass oil at 0.02% provided the best balance of aroma, taste, and overall impression. Based on combined chemical, microbiological, and sensory outcomes, 0.02% lemongrass oil was identified as the most promising candidate for further development.