Effect of pH on chlorophyll degradation and colour loss in blanched green peas

Effect of pH on the chlorophyll degradation and visual green colour loss in blanched green peas were studied at 70, 80, 90 and 100 °C in buffered solutions of pH 5.5, 6.5 and 7.5. The degradation of chlorophylls a and b followed a first-order reaction and the temperature-dependence of these reactions was modelled by the Arrhenius equation. The activation energies ranged from 4.80 ± 0.91 to 14.0 ± 0.71 kcal mol⁻¹ for chlorophyll a and from 6.84 ± 0.29 to 11.0 ± 1.06 for chlorophyll b with varying pH values. The visual green colour degradation, as represented by the change of the −a (greenness), the ratio −a/b and hue (h) values measured by tristimulus colorimeter, also followed a first-order reaction. Activation energies for −a values ranged from 8.13 ± 0.71 to 12.0 ± 1.07 kcal mol⁻¹, and for −a/b values ranged from 8.77 ± 1.34 to 12.0 ± 1.07 kcal mol⁻¹ with varying pH values at 70, 80, 90 and 100 °C.