After 72 h of fermentation, the pH level of fermen-tation medium was measured using a pH meter(Metrohm Siam, Thailand). Then, free lactic acid wasreleased from calcium lactate salt by adding proper amountof 4 M HCl to lower the sample pH level to 1.8-2.0.Subsequently, distilled water was added to make equalvolume of each sample and samples were centrifuged at6,000 rpm for 15 min. Lactic acid concentration in thesupernatant was analyzed by the method described byBarker and Summerson (14) whereas DNS method (15)and PGO enzyme preparation were used to determinereducing sugars and glucose levels, respectively. Briefly,sample and DNS reagent (1 ml each) were mixed, boiledfor 10 min, cooled down and added with 10 ml distilledwater. Then, the solution absorbance was detected at 540nm for reducing sugars determination. For glucose deter-mination, 0.25 ml of sample was mixed with 2.5 ml of PGOenzyme reagent containing o-Dianisidine. The reactionwas allowed at 37oC for 30 min before measuring theabsorbance at 425 nm.