Chemical and microbiological analysis of fermented probiotic watermelon juice

Abstract

Fruit juice is an ideal medium in the production of a probiotic drink. Watermelon fruit is a suitable medium for the production of probiotic juice due to its nutritional content. However, its utilisation as a probiotic drink is underutilised. Experiments were conducted to determine the chemical (pH, Brix, titrable acidity) and microbiological changes (lactic acid bacteria (LAB) count) during fermentation of probiotic watermelon juice using different concentrations of Lactobacillus plantarum, Lactobacillus paracasei and Lactobacillus acidophilus (2%, 5% and 10%) at 30°C for 72 hrs. The results indicated a significant drop in pH of the probioticated watermelon juice (2%, 5% and 10%) using various Lactobacilli strains during 24 hrs of fermentation. Interestingly, 2% probioticated watermelon juice in all their strains of probiotic were higher than 5% and 10% probioticated watermelon juice. The lactic acid content in probioticated watermelon juice was reduced significantly throughout 72 hrs of fermentation, but the watermelon juice without probiotic strains increased only within 24 hrs of fermentation. The LAB count in probioticated watermelon juice (2%, 5% and 10%) maintained a high population count (108 to 109 CFU/mL) for all probiotic strains throughout fermentation. Since all concentrations studied showed similar results in the chemical and microbiological analyses, 2% concentration is proven to be sufficient for probioticated watermelon juice regardless of the types of Lactobacillus strains used.