Effects of Intensified Fermentation on the Components of Noni Fruit and Its Antioxidant Activity

In this paper, on the basis of natural fermentation of noni fruit, Lactobacillus plantarum was inoculated to strengthen the fermentation process, and the changes of physical and chemical indexes, active components and antioxidant capacity of noni fruit were monitored and analyzed, so as to provide technological and technical references for the industrialized production of high-quality noni fruit fermentation broth. The total quality of noni juice reached the highest after 23 days of intensive fermentation:The pH of noni juice decreased from 4.23 to 3.53, the total acid content increased from 7.99 mg/mL to 14.95 mg/mL, the soluble protein decreased from 0.89 mg/mL to 0.19 mg/mL, and the total sugar decreased from 38.13 mg/mL to 25.14 mg/mL.The highest content of total phenols and total flavonoids reached 15.538 and 0.542 mg/mL, respectively, which were significantly higher than those in the natural fermentation group (P<0.05). Quercetin was 7 times higher than the original content. The butyric acid content of noni fermentation juice was significantly lower than those of NF group (P<0.05). In vitro antioxidant test, the total antioxidant capacity, DPPH free radical scavenging rate and hydroxyl free radical scavenging rate of the intensified fermentation group (IF group) were all higher than those of NF group, and significantly higher than that of noni fresh fruit (P<0.05).In conclusion, intensified fermentation for 23 d was selected as the end point of intensified fermentation of noni fruit. At this time, compared with NF group, the content of active ingredients and antioxidant capacity of noni fruit were significantly improved. The obtained noni fermentation juice was rich in nutrition and mild in flavor, which could be used as an optimal process for industrial fermentation of noni fruit.