Volatile profile of cork as a tool for classification of natural cork stoppers.

An untargeted approach, focused in the profile of volatile organic compounds (VOCs), was applied to differentiate natural cork stoppers with different levels of porosity, coded as Group 1 (low porosity), Group 2 (intermediate porosity) and Group 3 (high porosity). Statistically significant alterations were found in the levels of several VOCs between cork stoppers of low and intermediate porosity when compared with those of high porosity (Group 1 vs. 3 and Group 2 vs. 3). In addition, the levels of 2-pentylfuran, cyclene, camphene, camphor, limonene and eucalyptol enabled the discrimination of cork stoppers with low porosity (Group 1) into two subgroups, while furfural and 5-methyl-2-furfural enabled the discrimination of subgroups within the intermediate and high porosity stoppers (Group 2 and 3). A headspace solid-phase microextraction coupled to gas chromatography tandem mass spectrometry (HS-SPME-GC-MS/MS) method was developed to quantify the subgroup discriminant compounds, which may provide a proof-of-concept for the development of an efficient method to be applied in cork industry.