DEGRADATION KINETICS OF CHLOROPHYLLS AND CHLOROPHYLLIDES

Thermal degradation of chlorophylls and chlorophyllides in spinach puree was studied from 100 to 145-degrees-C (2-25 min) for chlorophylls and from 80 to 115-degrees-C (2.5-39 min) for chlorophyllides. The derivatives formed were: pheophorbides, pyropheophorbides, pheophytins and pyropheophytins. Degradation kinetics of chlorophylls and chlorophyllides followed a first-order kinetic model. Reaction rate data showed that the a form of both chlorophylls and chlorophyllides degraded more rapidly than the b form. Chlorophyllides were less stable than chlorophylls. Activation energies ranged from 15.0 to 22.8 Kcal/mol. A kinetic compensation effect was observed for both chlorophylls and chlorophyllides with an isokinetic temperature of 160.8-degrees-C. The relative stability of these compounds suggests that methods to maximize chlorophyllides would not be effective for improving green color stability.