Volatile free fatty acids as ripening indicators for Serra da Estrela cheese

Serra da Estrela cheese is an artisanal cheese manufactured from raw ewe's milk coagulated with Cynara cardunculus; it is highly appreciated for its unique flavor and bouquet. This research effort focused on a search for the molecules responsible for those organoleptic characteristics. Eighty cheeses manufactured in 4 dairies located in the Appelation d'Origine Protegee region of Serra da Estrela, Portugal, were thus assayed for volatiles, in an attempt to characterize their odorous profile. Cheeses were analyzed from the time of manufacture up to 180 d of ripening. The volatile fraction was assayed by solid phase microextraction-gas chromatography/mass spectroscopy, and several compounds belonging to different chemical groups (e.g., fatty acids, esters, carbonyl compounds, pyrazines, and sulfur compounds) were detected in that traditional cheese. Among these, free fatty acids (FFA) were quantitatively the dominant family present. Furthermore, sensory descriptors for the typical aroma of this cheese included acidic, sweaty, and sheepy-like. Acetic, isobutyric, and isovaleric acids increased in concentration during the ripening process up to 90 d, and remained constant thereafter. Preliminary sensory analysis was performed by addition of the major FFA to an unripened cheese matrix; results showed that they could successfully be used as ripening indicators for this cheese. Such key molecules may thus be used to monitor ripening, and hence find the optimal consumption time for this gourmet dairy product.