Optimization of Fermentation Process of Carrot Juice by Probiotics and Analysis of Aroma Components

Carrot juice was fermented by probiotic Lactobacillus casei (CTCF-LC1) and Lactobacillus reuteri (CTCF-LT1) with sensory score as the main evaluation index, and the fermentation process was optimized by single factor and response surface experiments. The optimum ratio of fermentative strains CTCF-LC1:CTCF-LT1 was 1: 1, fermentation time was 8 h, inoculum size was 3.1% and fermentation temperature was 26.6℃. Under the optimum conditions, the sensory score of fermented carrot juice was 91.3, pH was 4.50, total acid content was 3.73 g/L, total sugar content was 54.25 g/L, and reducing sugar content was 28.41 g/L. The carrot juice has bright orange color and stable state. It not only has the fresh flavor of fruit and vegetable juice, but also has the unique aroma from lactic acid bacteria fermentation, as well as soft and even taste, moderate acidity and sweetness. The changes of aroma components of carrot juice before and after fermentation were analyzed by headspace solid phase microextraction (HSPME) coupled with gas chromatography-mass spectrometry (GC-MS). After fermentation, substances with medicinal flavor components were reduced, and a lot of floral and fruit-scented substances were produced, such as methyl myristate, β-pinene, phenylethanol, and geraniol. Therefore, the results of this study can provide a theoretical basis for the development of fermented fruit and vegetable juice products with unique flavor substances.