Change in pH of black glutinous rice during 10-day fermentation indicating the progress of
fermentation process is shown in Figure 1A. At 0 day of fermentation, the pH of cooked black glutinous
rice was 5.83. During fermentation, yeast could play an important role for fermentation system which
ferments monosaccharide or sugar to alcohols and acids (Manosroi et al., 2011). The reduction of pH of
fermented rice was probably due the formation of acids by yeasts utilized carbohydrate. The pH of
sample decreased to 4.5 within 4 days of fermentation. Additionally, Manosiri et al. (2011) reported that
the pH of purple glutinous rice decreased to 4.4 within 6 days of fermentation. The lowered pH
indicated the safety of the product as determined by TCPS 162 (2003).