Ethanol in Olive Fruit. Changes during Ripening

Ethanol is one of the precursors of ethyl esters, the virgin olive oil quality parameter for the "extra" category recently adopted by the European Union and International Olive Oil Council. Although ethyl ester content has great importance for virgin olive oil classification, the origin of ethanol is not clear. A possible source of ethanol may be the olive fruit itself while it remains on the tree. Variation of fruit ethanol content during ripening was studied for three different olive cultivars: 'Picual', 'Hojiblanca', and 'Arbequina'. Ethanol was measured in fruit homogenates by HS-SPME-GC-FID. The ethanol content varied between 0.56 and 58 mg/kg. 'Hojiblanca' fruits showed the highest ethanol concentration. For all of the cultivars, ethanol content of fruit increased during the ripening process, although a clear cultivar-dependent effect was observed because 'Hojiblanca' fruits showed the most significant raise. Therefore, results indicated that ethanol can be accumulated during fruit maturation on the olive tree.