Selection of High Acid Producing Lactic Acid Bacteria and Potential Application in Pineapple Juice Fermentation

Lactic acid bacteria are used popularly for fruit juice fermentation because they are good sources of probiotics for human. In this study, ten lactic acid bacteria were isolated from 7 samples of naturally fermented pineapple juice. All isolates could grow in the MRS medium pH 1.5 and reach high densities (6.80 – 6.95 log CFU/mL) after 2 h of incubation at 37°C. Moreover, Lactobacillus sp. Y1 produced highest lactic acid concentration (1.20% w/v) and identified as L. acidophilus . The different diluted ratios of pineapple juice (0, 10, 20 and 30% w/v) and different sucrose supplementations (0, 3, 6, and 9% w/v) were used for testing fermenting capacity of L. acidophilus Y1. The undiluted pineapple juice with 9% (w/v) of sucrose supplementation was found to be suitable for fermentation. Based on the results of sensory evaluation and bacterial density determination, the favorable conditions for pineapple fermentation were determined as follow: initial bacterial level at 5.0 log cells/mL, fermentation time for 36 h at 37°C. The results of storage testing showed that the suitable temperature for product storage was 4 – 6°C, bacterial density (8.06 log CFU/mL) of final product was maintained up to 3 weeks.