DISAPPEARANCE OF CHLOROPHYLLS AND CAROTENOIDS DURING THE RIPENING OF THE OLIVE

Although the colour of olives changes from green to yellow, turning colour, purple and black according to the stage of ripeness, chlorophyll a is always the major chloroplastic pigment followed by chlorophyll b. Carotenoids are also present as minor components. Among these, lutein and beta-carotene are worthy of mention, while neoxanthin, violaxanthin and antheraxanthin are present in lower proportions. The concentration of the chlorophylls and the carotenoids decreases gradually as harvesting approaches. When the colour of the fruit is predominantly green, the percentage decrease of the carotenoid fraction is higher than that experienced by the chlorophyll fraction. In the latter fraction at this stage chlorophyll b is preferentially degraded. In contrast, in the yellow colour stage, the disappearance of chlorophylls is noticeably higher than that of carotenoids, the levels of which tend to be maintained with minimal pigment degradation at this stage. This faster degradation of the chlorophylls allows the coloration due to the carotenoids to be seen in the fruit. From this moment onwards, once the stage of ripening has begun, the rate of degradation of the chlorophyll fraction increases to almost twice that of the carotenoid fraction, and chlorophyll a disappears faster than chlorophyll b. The ratio of lutein to beta-carotene decreases as ripening advances reflecting the higher rate of degradation of lutein.