MECHANISM AND KINETICS OF THE DEGRADATION OF CHLOROPHYLLS DURING THE PROCESSING OF GREEN TABLE OLIVES

During the process of olive fermentation chlorophylls are transformed into pheophytins and pheophorbides. Chlorophyllides were detected as intermediate products. Research into the origin of these structural modifications has shown that the chlorophyllides are formed from the chlorophylls by the action of chlorophyllase, while it is the acid environment developed during fermentation that facilitates the interchange of magnesium ions for those of hydrogen in all of the porphyrin compounds present. The kinetic study carried out has shown that the degradation of chlorophylls to pheophytins and of chlorophyllides to pheophorbides fits first-order kinetics with respect to the pigment concentration. The degradation mechanism proposed is as follows: first stage (time = t(chlase)), [chlorophylls] --> [chlorophyllides] (k(1)); second stage (time > t(chlase)), [chlorophyllides] --> [pheophorbides] (k(2)) and [chlorophylls] --> [pheophytins] (k(3)). While the enzyme chlorophyllase is active (time = t(chlase)), a proportion of the chlorophylls give rise to chlorophyllides. The remaining chlorophylls have not at this stage been affected by the action of the enzyme, and these constitute substrate available for the subsequent pheophytinization reaction. This begins once the active phase of the chlorophyllase enzyme has finished and takes place in parallel with the formation of pheophorbides. The latter compounds arise only from the chlorphyllides formed as a result of chlorophyllase action.