Effects of time, temperature and inoculum volume of permentation using lactobacillus plantarum on bioactive compounds of bitter gound (Momordica charantia) juice

Abstract

Effects of fermentation factors including time (0, 12, 24, 36, 48, 60 and 72h), temperature (20, 25, 30, 35 and 40 ) and inoculum volume (v/w) (0, 1, 5, 10, 15 and 20%) on the bioactive compounds of bitter gourd juice using Lactobacillus plantarum were studied in this research. Determination of pH, total soluble solids (TSS), total phenolic contents (TPC), antioxidant capacity (AC), charantin content and level of bitterness were carried out. In general, the TPC and AC values of fermented samples increased significantly (p<0.05) compared to the control ones. In the first experiment, the TPC value of 24h-fermented sample reached a peak of 12.12 0.03 mg GAE/ 100ml, meanwhile the highest AC value obtained after 72h fermentation (70.88 2.30 %). In the second experiment, the highest TPC and AC values were recorded at 40oC, with the TPC was 13.13 0.16 (mg GAE/ 100ml) and the DPPH scavenging effect was 73.42 0.99 (%). Meanwhile in the last experiment, with 20% inoculum volume, the highest TPC and AC values were 13.78 0.16 (mg GAE/ 100ml) and 70.93 3.12 (%), respectively. In addition, the charantin content of fermented juice were also recorded to be significantly higher (p<0.05) than control one in all three experiments. The values felt between 1.03 0.11 and 1.94 0.05 (mg/100ml). Through sensory evaluation test, significant differences (p<0.05) in the bitterness among unfermented and fermented samples were also recorded. Most of the panelists recognized there was reduction in bitterness of fermented sample compared to the control one. To sum up, fermentation process would significantly enhance the TPC and AC values, improve charantin content and reduce the level of bitterness of bitter gourd juice. Keywords: bitter gourd, charantin, Lactobacillus plantarum, juice processing, fermentation, bitterness, sensory evaluation.