Abstract: In order to investigate the effect of the addition of kefir on the quality of carrots fermented with Lactiplantibacillus plantarum x2 (Lp.x2), the physicochemical and textural properties, sensory evaluation and volatile flavor substances of carrots fermented with kefir and/or Lp.x2 were analyzed. The results showed that after 10 days of fermentation, Lp.x2 resulted in the lowest total acid content and moderate nitrite content, while kefir resulted in the highest total acid and the lowest nitrite, and the mixed culture fermentation was between the single culture fermentations. Compared with single Lp.x2 fermentation, the addition of kefir increased the total acid content by 18.46%–43.66% and reduced the nitrite content by up to 8.20%. In addition, it decreased the hardness of fermented carrots and increased the pectinase activity. The mixed culture fermentation with a mixing ratio of 50:1 between Lp.x2 and kefir had the highest sensory score of 80.80. Moreover, the addition of kefir favored the formation of flavor substances; a total of 58 flavor substances were detected in the mixed culture fermented sample, and 51 in the Lp.x2 fermented sample. Therefore, the addition of kefir could improve the eating characteristics of carrots fermented with Lp.x2, which was beneficial to the quality of fermented carrots. This study revealed the effect of kefir addition on the quality of fermented carrot, determined the optimal proportion of fermented carrot, filled the gap in the existing research, and had certain theoretical and practical value.

Key words: Lactiplantibacillus plantarum; kefir; carrot; fermentation