Solid-phase microextraction-mass spectrometry: a new approach to the rapid characterization of cheeses.

This work describes a new method for the rapid characterization of cheeses by solid-phase microextraction coupled with mass spectrometry (SPME-MS). After four types of fiber were tested and the main extraction parameters studied, the volatile components were extracted using a Carboxen/PDMS 75-microm fiber placed for 10 min at 20 degrees C in the headspace of the cheese. The substances adsorbed were then transferred directly from the injector to the inlet of a mass spectrometer through a 1-m deactivated silica capillary column heated to 210 degrees C. The mass spectra thus obtained without prior chromatographic separation formed a "fingerprint" of the analyzed sample. For data analysis, the mass fragments of each spectrum (45 < m/z < 150 amu) were considered as potential descriptors of the composition of the headspace of the cheeses. Stepwise discriminant analysis was used to select a limited number of mass fragments that afforded an operational classification of the batches of cheeses studied. This new method offers the advantage of minimizing thermal, mechanical, and chemical modifications of the matrix, thereby reducing the risk of analytical artifacts. SPME-MS provides a simple and effective approach to rapid quality control by analysis of the volatile fraction of foods.