Lactic acid fermentation of papaya juice using single and mixed Lactic acid bacteria

Abstract

Objective: Phytochemistry, microbiology, flavor and functional properties of fermented papaya juice were examined in relation to Lactobacillus plantarum (Lp), Lactobacillus rhamnosus (Lr), Lactobacillus acidophilus (La) and their mixed strains (Lp+Lr、Lp+La、Lr+La), in order to develop a probiotic papaya beverage with improved functionality and health-promoting properties. Methods: In thisstudy, changes in pH, total soluble solids, titratable acid, viable cells, glucose, fructose, sucrose, organic acids and volatile compounds were determined. The contents of total phenolics and total flavonoids, as well as the inhibitory activity against α-glucosidase and tyrosinase enzymes during the fermentation process, were also investigated. Results: The single-and mixed strain cultures showed similar changes during the 72 h fermentation period, exhibiting significantly decreased pH and increased acidity. The contents of lactic acid and succinic acid greatly increased, whereas that of citric acid and malic acid decreased significantly. After fermentation, the content of total phenolics and flavonoids increased in papaya juice. Pearson's correlation analysis revealed that the metabolism of phenolics likely contributed to enhancing the inhibitory activity against α-glucosidase and tyrosinase enzymes. Among all fermentation groups, the papaya juice fermented by Lp exhibited the highest contents of lactic acid, total phenolics, and flavonoids, showing the strongest inhibitory effect against α-glucosidase and tyrosinase enzyme. Additionally, six types of aromatic compounds were primarily detected in unfermented papaya juice, with butyric acid content being the highest (89.742%), followed by linalool. After fermentation, a total of 25 aromatic compounds were identified in the six fermented juice samples, and the content of butyric acid declined significantly, which reduced the unpleasant odor of papaya. In all fermentation groups, the Lp single-strain culture generated the most volatile components (18 types), while the Lp+Lr mixed culture achieved the lowest (5 types). Although the Lp+Lr mixed-strain culture had the highest number of viable bacteria [7.61 lg (CFU/mL)], the Lp single-strain culture may be preferable overall. Conclusion: The Lp single culture could improve the sensory characteristics of papaya juice and enhance its beneficial properties.

Keywords

• caricapapaya l.
• fermentation
• lactobacillus acidophilus
• lactobacillus plantarum
• lactobacillus rhamnosus