Optimization of fermentation process of tomato juice by lactic acid bacterium and its volatile flavor substances analysis

Fermented tomato juice was prepared by Lactobacillus acidophilus fermentation using processed tomato from Xinjiang as raw material, and the fermentation process was optimized by single factor and response surface tests. Furthermore, the volatile flavor substances in the tomato juice before and after fermentation were analyzed using solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the optimal fermentation process conditions of tomato juice fermented by lactic acid bacterium were as follows: inoculum 0.7 mg/ml, fermentation temperature 37 ℃, time 41 h, and initial soluble solids contents 13 °Bx. Under these optimal conditions, the viable number of fermented tomato juice was 9.02 lg (CFU/ml), and the sensory score was 88.9. Additionally, a total of 46 volatile flavor substances were detected in the tomato juice before and after fermentation, including 17 aldehydes, 13 alcohols, 4 ketones, 4 esters, 4 acids, and 4 others. Among them, the aldehydes and alcohols were the main volatile flavor substances, and 4-methyl benzaldehyde, isobutanol, linalool and ethyl acetate were characteristic aromatic substances.