Response Surface Optimization of the Fermentation Process of Tomato Juice by Lactobacillus plantarum and Its Quality Evaluation

A fermented beverage by Lactobacillus plantarum was developed using tomatoes as raw materials. Through single factor and response surface tests, the optimal fermentation process for tomato juice was determined as follows: Fermentation temperature of 37 ℃, bacterial inoculation of 2%, and fermentation time of 30 h. The results showed that during the fermentation process, the pH and the total sugar content of tomato juice decreased while the total acid content increased, and the number of viable bacteria initially increased (P<0.05) and then stabilized. After fermentation, the content of total phenols and total flavonoids in tomato juice significantly increased, and the scavenging rate of ABTS⁺ and DPPH free radicals also increased significantly, indicating that fermentation of tomato juice by Lactobacillus plantarum increased its antioxidant capacity. However, the lycopene and β-carotene content decreased as affected by processing and fermentation. The quality evaluation results of the final fermented tomato products after storage at 4 ℃ for 21 d showed that its sensory, hygienic and microbiological indicators were all up to the standards, and met the edible safety requirements of fermented fruit and vegetable juice.