In general, the pH played an important role in stabilizing
anthocyanins under a thermal treatment. A lower pH system
helped to reduce the thermal damages of anthocyanins, particularly
during a high temperature treatment. However, compared
to pH, temperature showed a bigger impact on the stability of
the two anthocyanins. The loss of the two anthocyanins caused
by an increase in temperature was much larger than that caused
by an increase in pH. The degradation rate constants of cyanidin-
3-glucoside and cyanidin-3-rutinoside were increased from 0.899
to 3.07 s1 and from 0.533 to 2.55 s1, respectively, with an
increase of pH from 2.2 to 6.0 at 100 C. In comparison, at pH
2.2, the increase of temperature from 100 to 165 C caused faster
increases of the degradation rate constants of the two anthocyanins
from 0.899 to 90.54 s1 for cyanidin-3-glucoside and from
0.533 to 43.3 s1 for cyanidin-3-rutinoside. These results again
clearly showed that the temperature had a greater impact on the
stability of the two anthocyanins than pH. Therefore, to retain
more anthocyanins in processed foods of pH 6 6, the priority
should be to firstly minimise thermal damages during food processing,
and then to low down the pH of the food.