Effects of different lactic acid bacteria on phenolics, aroma-active compounds, and other quality parameters in beet kvass production

In this study, the effects of different lactic acid bacteria (LAB) strains on the fermentation duration of red beet (Beta vulgaris var. Conditiva), and on various quality attributes of the resulting beet kvass product—such as antioxidant activity, total phenolic content, color characteristics, microbial flora, phenolic compound profile, aroma and aroma-active components, sensory properties, and mineral element content—were investigated for the first time. The study included a control sample (K) subjected to spontaneous fermentation, and three inoculated samples produced by adding 1% (v/v) of Lactobacillus casei (ATCC 431), Lactobacillus delbrueckii (ATCC 9649) and Lactobacillus plantarum (ATCC 14917) at the initial stage of kvass production, coded as LC, LD, and LP, respectively. Antioxidant capacity was assessed using the DPPH and ABTS methods, while total phenolic content (TPC) was measured using the Folin-Ciocalteu method. The results revealed that the addition of the LP strain significantly and positively influenced antioxidant capacity, while both LP and LD strains had a pronounced effect on TPC. Betacyanins, betaxanthins, and other betalain group compounds present in the beet kvass samples were identified and quantified using LC-DAD-ESI-MS/MS. A total of 15 phenolic compounds were identified, and in line with TPC results, the phenolic profiles of the LAB-inoculated samples exhibited significant differences compared to the control group. In particular, fermentation with L. plantarum led to an approximately fourfold increase in total betacyanin content and a twofold increase in betaxanthin content. Aroma profiles were determined using the SAFE (Solvent Assisted Flavor Evaporation) method, while aroma-active compounds were analyzed using AEDA (Aroma Extract Dilution Analysis) and GC-MS/Olfactometry. As with the phenolic profiles, the aroma and aroma-active profiles varied significantly across the LAB-fermented samples. A total of 46 aroma compounds were identified, with significantly higher total aroma compound concentrations observed in the LP and LD samples compared to K and LC. Ketones and carboxylic acids were identified as the dominant aroma groups in all samples. Additionally, 20 aroma-active compounds were identified through GC-MS/O analysis. Descriptive sensory analysis showed that among the four products, the LP sample received the highest scores from panelists in terms of aroma, taste, and overall acceptability. Overall, the use of different LAB strains in red beet kvass production had significant and favorable impacts on fermentation time, color, antioxidant capacity, phenolic and aroma-active compounds, sensory quality, and mineral composition, resulting in superior product quality compared to spontaneous fermentation.