Figures 1 and 2 show aqueous anthocyanin extracts at different pH values after 1 h of equilibration
(Figure 1) and after 28 days of storage at 25ºC in the dark (Figure 2). pH 1 to 4 showed colour
retention during the four weeks storage period at 25ºC in the dark. The colour for pH 5 to 10 faded
to yellowish after one week. Extract at pH 5 and 6 became colourless after 3 weeks. The results of
absorbance at day 1 and after 28 days for all pH conditions followed first order kinetics with R2
>
0.8357. From the results (data not shown), percentage of absorbance changes at λmax is higher at pH
1 (64.79%) with R2
= 0.9251 while the lowest at pH 8 (17.61%) with R2
= 0.9993. This clearly
indicates that anthocyanin stability decreased with increasing pH values.