Lactic acid fermentation as a tool to enhance the antioxidant properties of Opuntia ficus-indica juice

Abstract

Lactic acid fermentation of Opuntia ficus-indica fruit juice constitutes an important biotechnology process for its preservation. The aim of this study was to evaluate the effect of lactic acid bacterial (LAB) fermentation of cactus pear juice (CPJ) on its properties. Variations in radical scavenging activity, phenolic compound contents, betalain contents, pH and acidity were compared after fermentation taking fresh fruit juice as control. CPJ were fermented with Weissella cibaria and also with Pediococcus pentosaceus. These strains were previously isolated from CPJ in our laboratory. CPJ was inoculated with LAB (2% of inoculum) and incubated for 24 h at 25°C. Pasteurized CPJ not inoculated with the LAB was submitted to the same treatment and used as control. pH values and LAB counts (CFU/ml) in CPJ were measured at 6, 12, 18 and 24 h of incubation. Phenolic compound concentrations (PCC) were assayed by the Folin-Ciocalteu method. DPPH bleaching method was used to evaluate radical scavenging activity. P. pentosaceus was able to acidify the juice with a pH decrease from 4.96 to 4.15 after 24 h of growth at 25°C and production of 4.10 g L-1 of lactic acid. PCC and betalain contents were preserved after lactic acid fermentation. Additionally, fermented cactus pear juice by P. pentosaceus strain showed similar antioxidant activity to the control juice, although, the juice fermented with W. cibaria strain, showed significantly (P<0.05) higher activity than the control juice. The selected strains exhibited a good performance for their use in the fermentation of CPJ.