Relationship between aroma components and malaxation time of olive paste

The volatile compounds determination of olive oils extracted from two Italian varieties, "Coratina" and "Frantoio", at different malaxation times, was carried out. The volatile fraction was mainly formed by C6, compounds arising from the hydroperoxide lyase cascade and by C5 compounds deriving principally from a β-scission mechanism involving a LOX-mediated cleavage of linolenic acid 13-hydroperoxides. In addition, metabolites which derive from the degradation of some aminoacids and from the fermentation of sugars naturally occurring in the fruits, were detected. Quantitation of C5 and C6 components were performed by use of the recovery factors of each metabolite from the oily matrix. Data obtained pointed out that the amount of each volatile increased with the prolonging of malaxation time and the most important change was shown by the trans-2-hexenal content. An opposite trend was recorded for the C6 ester content, which underwent a very considerable decrease after 30 minutes of malaxation. Furthermore it has been evidenced that, among the different pathways involved in the volatile biogeneration, the most active was ascribable, for both varieties, to hydroperoxide lyase cascade, since trans-2-hexenal and hexanal represent the main accumulation products, specially in the Frantoio variety. The sensory evaluation of oils extracted at different malaxation times pointed out, in addition to a considerable decrease of the intensities of bitter and pungent descriptors, a weakening of some perceptions related to "green" notes, as the malaxation time was prolonged.