Figure 3 shows k-values for rate of reaction of aqueous anthocyanin extracts after 28 days of
storage at different pH. pH 1 to 4 showed colour retention during the four weeks storage period at
25ºC in the dark, which is in agreement with earlier findings on the change in absorbance
percentages of more than 45% compared to less than 45% for pH between 5 to 10. Therefore,
further evaluation on the thermal stability of the aqueous extracts will be carried out at pH 3 since
most food products are in the pH range from 3 to 7 [12].