A novel strategy for improving the antioxidant, iridoid, and flavor properties of Noni (Morinda citrifolia L.) fruit juice by lactic acid bacteria fermentation

Noni ( Morinda citrifolia L.) fruit juice (NFJ) has an unpleasant flavor but is highly bioactive, so it is necessary to improve the quality of NFJ by exploring a novel strategy. The effects of eight lactic acid bacteria (LAB) on the antioxidant, phenolic, iridoid, and flavor properties of NFJ were investigated in the present study. The results showed that antioxidant activity was improved after NFJ fermentation by LAB and that L. rhamnosus had the highest free radical scavenging activity. The highest total phenolic content and total flavonoid content were in L. brevis- fermented NFJ (78.85 mg gallic acid equivalent/100 mL and 37.12 mg rutin equivalent/100 mL, respectively). Bioconversion of iridoid revealed that deacetylasperulosidic acid can be deacetylated from asperulosidic acid. Furthermore, LAB fermentation presented a significant decrease in unpleasant butanoic acid, with the lowest content found in L. fermentum- fermented NFJ. This research provides progressive information on the application of LAB culture in NFJ fermentation.