Solid-phase microextraction of volatile compounds in "Terrincho" ewe cheese. Comparison of different fibers.

Solid-phase microextraction coupled to gas chromatography-mass spectrometry (GC-MS) was applied to study the volatile compounds in "Terrincho" ewe cheese. Six types of fibers were tested and the main extraction parameters were studied. Carboxen-polydimethylsiloxane fiber 75 microm (CAR-PDMS) achieved the most complete profile of ewe cheese volatile compounds. The optimised conditions used for characterization of "Terrincho" ewe cheese were: sample vial equilibration at 20 degrees C for 20 min, followed by CAR-PDMS fiber exposure to the headspace above the sample for 30 min and finally thermal desorption of the adsorbed substances, in the injector port for GC-MS analysis. This technique was a useful tool for the differentiation of 11 "Terrincho" ewe cheeses, all taken from the same cheesemaking season with 30 days of ripening but from three different farmhouses, according to their volatile fraction. Results obtained were statistically treated by categorical principal component analysis. Subsequently, 49.15% of the variation in data was due to the first dimension (k = 12.7) and the second dimension (k = 8.88) accounted for 34.2% of the total information. Volatile profiles among samples indicated cheese group separation according to farmhouse of production.