Lactic Acid Fermentation of Carrot Juice: Effects of LAB Strains, Total Soluble Solids, Inoculum Level, and Fermentation Time.

Carrot juice is a promising substrate for developing functional fermented beverages; however, optimal conditions for lactic acid fermentation remain insufficiently defined. This study investigated the effects of lactic acid bacteria (LAB) strains, juice dilution ratio, initial total soluble solids (TSS, °Brix), inoculum level, and fermentation time on the fermentation performance and quality of carrot juice. Ten LAB strains previously isolated from fermented tomato products were screened, among which strain TO35 exhibited the highest lactic acid production (12.37 ± 0.45 g/L). Juice dilution significantly influenced fermentation efficiency, with undiluted and 1:1 diluted formulations showing superior acidification performance compared with higher dilution levels. The combination of 15°Brix and 3% (v/v) inoculum resulted in maximal lactic acid production (14.10 g/L) and high LAB viability. Fermentation time markedly affected biochemical and sensory attributes. Although prolonged fermentation (48-72 h) further increased lactic acid production, it led to excessive acidification and reduced sensory acceptability. Therefore, fermentation for 24 h yielded the highest sensory acceptance, characterized by typical carrot color, balanced aroma, and minimal visible sedimentation, contributing to acceptable sensory quality. Overall, lactic acid fermentation of carrot juice was optimally achieved using a 3% TO35 inoculum at 15°Brix with a fermentation duration of 24 h. These findings provide useful insights for the development of carrot-based lactic fermented beverages with improved sensory quality and functional potential.