Characterization of olive ripeness by green aroma compounds of virgin olive oil

The evolution of the volatile compounds responsible for virgin olive oil green aroma has been studied in samples obtained from four olive fruit varieties (Arbequina and Picual, Spain; Koroneiki, Greece; and Coratina, Italy), picked at three different stages of ripeness during two consecutive crops. The volatile compounds hexanal, (E)-3-hexenal, (Z)-3-hexenal, (E)-2-hexenal, hexyl acetate, (Z)-3-hexenyl acetate, hexan-1-ol, (E)-3-hexen-1-ol, (Z)-3-hexen-1-ol, and (E)-2-hexen-1-ol were considered in this study. The sensory significance of these volatile compounds has been stated by their odor activity value (OAV), while their synergic relationships with green sensory attributes have been analyzed by principal component analysis, The stages of ripeness of each variety, with the whole set of volatile compounds, were characterized by cluster analysis. Detailed information corresponding to each volatile compound for each stage of ripeness, aft;er fuzzy filtering of the quantitative data, has also been established. Alcohols produced from linolenic acid (E)-3-hexen-1-ol, (Z)-3-hexen-1-ol, and (E)-2-hexen-1-ol, and hexanal and hexyl acetate-both produced from linoleic acid-are major contributors to the ripeness characterization. The results were verified by applying multiple regression to the quantitative values of volatile compounds of a test set of eight Arbequina samples picked each fortnight from unripened to over-ripened olives. From the results of this study it can be concluded that the unripe stage is the best characterized, although the result in prediction for three stages of ripeness was an adjusted R-2 value of 0.98.