Changes in the volatile profile of citrus fruit submitted to postharvest degreening treatment

Despite citrus fruit are considered as non climacteric, ethylene is effectively used to accelerate external colour change of early-season citrus fruit in the Mediterranean area and is generally assumed to have no effect on internal fruit ripening. In this study we investigated if this postharvest degreening treatment has any effect on the volatile profile of early-season citrus fruit. The experiment was carried out under commercial conditions, thus a quarantine treatment was also simulated. Degreening of early-season citrus varieties ('Navelina' oranges (Citrus sinensis (L.) Osbeck), 'Clemenules' and 'Oronules' mandarins (Citrus reticulata Blanco) and three mutations of 'Oronules' namely 'Prenules', 'Basol' and 'Clemenrubí') with ethylene produced reproducible and variety-specific changes in the levels of fruit volatiles. The volatile profile in response to ethylene in 'Oronules' and 'Clemenrubí' presented quite dramatic changes with higher levels of some esters such as ethyl propionate and ethyl octanoate. The volatile profile of 'Navelina', 'Prenules' and 'Basol' was only slightly affected by ethylene exposure and Clemenules' did not show significant differences in the levels of aroma active compounds between degreened and control fruit, as would be expected for non climacteric fruits. On the whole, the results indicate that despite citrus being a non climacteric fruit some aspects of its ripening could be still sensitive to external exposure to ethylene.