Exploitation of the health-promoting and sensory properties of organic pomegranate (Punica granatum L.) juice through lactic acid fermentation

• Lactobacillus plantarum POM1 and C2 were suitable starters for pomegranate juice fermentation.
• Pomegranate juice highlighted some peculiar metabolic traits of lactic acid bacteria.
• Lactic acid fermentation increased the concentration of ellagic acid.
• The fermented pomegranate juice improved health-promoting, sensory and preservative features.

Two strains (POM1 and C2) or LP09 of Lactobacillus plantarum, which were previously isolated from tomatoes and carrots, and another commercial strain of L. plantarum (LP09), were selected to singly ferment (30 °C for 120 h) pomegranate juice (PJ) under standardized protocol. PJs were further stored at 4 °C for 30 days. Filtered PJ, not added of starters (unstarted PJ), was used as the control. After fermentation, all starters grew to ca. 9.0 Log CFU/mL. Viable cells of strain LP09 sharply decreased during storage. The other two strains survived to ca. 7.0 and 8.0 Log CFU/mL. Lactic acid bacteria consumed glucose, fructose, malic acid, and branched chain and aromatic amino acids. The concentration of free fatty acids increased for all started PJs. Compared to unstarted PJ, color and browning indexes of fermented PJs were preferable. The concentration of total polyphenolic compounds and antioxidant activity were the highest for started PJs, with some differences that depended on the starter used. Fermentation increased the concentration of ellagic acid, and enhanced the antimicrobial activity. Fermented PJs scavenged the reactive oxygen species generated by H2O2 and modulated the synthesis of immune-mediators from peripheral blood mononuclear cells (PBMC). Unstarted and fermented PJs inhibited the growth of K562 tumor cells. The sensory attributes of fermented PJs were preferred. The fermentation of pomegranate juice would represent a novel technology option, which joins health-promoting, sensory and preservative features to exploit the potential of pomegranate fruits.