Relationship between fruit ripening and aroma compounds of olives from Guercif area in Morocco

Abstract

Green olives are characterized by a typical flavour mainly due to compounds formed during fruit ripening. Our previous studies have shown that the (Z)-3-hexenal, methional, guaiacol, (E,E)-2,4-decadienal and other terpenes such as α-farnesene significantly contribute to the olive aroma. In the present study, the impact of ripening stage on the aromatic composition of the green olives in Guercif area was evaluated. The extraction of flavours from samples collected at different stages of maturation was performed by simultaneous steam distillation-solvent extraction. The extracts were analyzed by GC-MS and GC-FID-O. The results showed that proportions of odorant compounds with sensory impact on the Moroccan green olives such as (Z)-3-hexenal/hexanal and methional, increased during fruit ripening. The olive fruit sam-ples from area of Guercif were characterized by the dominance of mono-and sesquiterpenes such as γ-terpinene, 3-carene, α-pinene, limonene, 3,7-dimethyl-1,3,7-octatriene, α-farnesene, β-caryophyllene and α-humulene. The monitoring of the aroma composition during olive ripening stage showed that the proportion of the 3,7-dimethyl-1,3,7-octatriene strongly decreases during maturation while the proportions of other monoterpenes characterized by olfactory notes of lemon, green and floral such as γ-terpinene, 3-carene and α-pinene are more important in the final stage of maturation. For the sesquiterpenes class, the formation of β-caryophyllene and α-humulene decreases in favour of the α-farnesene, important aroma compound of table olives. The comparison of volatile fraction of fresh olives at different stages of maturation showed that fruit ripening has an important impact on the formation of aromatic compounds and particularly the key flavours of green olives.