Improving the functional components and biological activities of navel orange juice through fermentation with an autochthonous strain Lactiplantibacillus paraplantarum M23

The fermentation of navel orange juice with lactic acid bacteria (LAB) has rarely been investigated. In this study, an autochthonous LAB strain isolated from navel orange, Lactiplantibacillus paraplantarum M23, was found to effectively ferment navel orange juice, producing a juice with enhanced functional activities and organoleptic quality. The viable bacterial count in the fermented orange juice remained consistently above 8.51 log CFU/mL throughout the entire 7-day fermentation period. The content of vitamin C (VC), total phenolic content (TPC), total flavonoid content (TFC), and hesperidin in the fermented orange juice increased by a maximum of 28.88, 1.21, 1.13, and 1.16 times, respectively, compared to the unfermented orange juice. The fermented juice exhibited significantly higher antioxidant activity than the unfermented juice, with an increase of up to 255 % and 347 % based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP) assays, respectively. This may be attributed to the increase in VC and flavonoids, as demonstrated by Pearson's correlation analysis. Additionally, the fermented orange juice demonstrated improved α-glucosidase inhibition, anti-MRSA, and anti-glycation activities compared to the unfermented juice. Furthermore, the fermented juice notably reduced the levels of NO and ROS in Raw 264.7 cells without any negative impact on cell viability. The findings of this study may help in the development of nutritious and healthy fermented navel orange juice products, and serve as a reference for the production of fermented beverages from other fruits using autochthonous strains.