Towards a technological ripening index for olive oil fruits

BACKGROUND The aim of this work was to study the evolution of sugar and oil contents in Frantoio cultivar olives during ripening to propose a technological ripening index for olive oil fruits. Olive fruits were picked in nine different farms once a week from the beginning of September to the beginning of December during three crop seasons. RESULTS As a result of the biochemical phenomenon of oil formation in olive fruits, sugar concentration during ripening was shown to follow a sigmoidal decrease, which recurred periodically in different microclimates over years. This trend resulted to be the cause of an opposite sigmoidal increase in the oil content. Experimental data for sugar and oil contents were also statistically related by significant linear relationships. It was also observed that reaching minimum environmental temperatures ≤ 10°C resulted in a definite minimum asymptotic value for sugars. CONCLUSION Sugar concentration was proposed as an accurate, reproducible index for technological ripening of olive oil fruits by the following prediction function: Proper ripening degree of olives corresponds to achievement of a minimum, constant value for sugar content and, consequently, a maximum, constant value for oil content, associated with reduced risks of fermentation activities of olive paste.