Effect of Inulin Concentration on the Growth of Lactobacillus Casei in Fermented Red Dragon Fruit Juice

Lee, Eugene (2018) Effect of Inulin Concentration on the Growth of Lactobacillus Casei in Fermented Red Dragon Fruit Juice. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

In this study, red dragon fruit juice is used as a medium to undergo lactic acid bacteria fermentation instead of using dairy as medium to prevent problems of dairy allergens. Lactobacillus casei was inoculated into the red dragon fruit juice and different concentrations of inulin which is a type of prebiotic was added into the juice samples to study its effect of promoting the growth of L. casei during the fermentation process. The red dragon fruit juice is firstly prepared and centrifuged to obtain a clear juice samples. Addition of different concentrations of inulin [2%, 4% and 6% (w/v)] into the fruit juice was done followed by pasteurization of the juice. L. casei inoculum was prepared and inoculated into the red dragon fruit juice samples with different inulin concentrations. Samples were then incubated under microaerophilic condition at 37°C for time interval of 0 to 3 days. Control sample without inulin underwent same procedures as the samples above. Changes in viable cell count, pH, total titratable acidity, total soluble solid content and total sugar content were recorded between each day of the fermentation time interval. Statistical analysis with one-way ANOVA on mean comparison with confidence interval of 95% was done using MINITAB 17. The increments of the inulin concentration from 2%, 4% to 6% (w/v) give significant results on viable cell count and other physiochemical tests. The best was observed at Day 2 sample with 6% (w/v) inulin which obtain the most significant increment (11.31±0.01 log cfu/mL) on cell growth, lower pH value (4.06±0.01), higher TTA (0.42±0.01), higher decrement of total sugar content (15.74±0.02 g/100 mL) and increment on total phenolic content (196.49±16.08 GAE mg/100 mL) after day 2 fermentation. In conclusion, day 2 fermented juice sample with 6% (w/v) inulin added obtained the best results among all the juice samples. Wider range of inulin concentration can be done on further study to determine the most optimum concentration for maximum cell growth.