[PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Headspace Solid-Phase Microextraction: A Useful and Quick Tool for the Traceability and Quality Assessment of Wine Cork Stoppers
being a very useful tool when establishing these parameters. Natural cork is mostly formed by two large polymers, suberin and lignin, and to a lesser extent, polysaccharides and a removable fraction with different solvents mostly formed by volatile compounds and phenolic compounds [1]. In natural corks, the qualities are visually established based on their external structure, with stoppers with the lowest number of external imperfections and/or lenticels being those of higher quality and, consequently, greater economic value. However, the migration of different organic compounds (volatile and phenolic compounds) to wine during its storage or aging is demonstrated [2; 3; 4; 5].  
The volatile fraction of a cork is constituted by a high number of compounds of different chemical natures, which come from the degradation of wood components such as fatty acids or lignin, or by the effect of microbial metabolism, mainly being molds that can grow in cork planks [6; 7; 8]. Among them, halonaisoles and halophenols are the most studied due to their implication in the \"cork taint\", although other volatile compounds such as geosmin, 1-octen-3-ol, 2-methyl-isoborneol and 2-methoxy-3,5-dimethylpyrazine are also responsible for negative attributes in wines, such as \"moldy\", \"green\" and \"chemical\" odors [5; 7; 9; 10].  
However, without considering the compounds responsible for the \"cork taint\" in wines, the volatile fractions of corks include many compounds that, even in small concentrations, could influence the final aroma of wines [11]. On the other hand, these volatile compounds come from cork planks and could be good indicators of their geographical origin [12; 13; 14]. Thus, the study of the volatile fraction of corks is presented as a new tool for the cork industry, which will allow it to establish the traceability of cork stoppers, as well as monitor the production process and the implementation of quality standards.  
Different analysis techniques have been used to analyze the volatile compounds of corks, normally based on extraction with organic solvents or on maceration in hydroalcoholic solutions similar to wine. However, headspace solid-phase microextraction (HS-SPME) is a fast and simple method that allows the analysis of the volatile fraction of solid samples without prior preparation. This technique has been used by our research group for the fast screening of the volatile compounds of oak wood [15] and has also been applied to cork stoppers [13; 16].  
The objective of this work is to analyze the volatile fraction of natural corks of different visual qualities (flower, superior, second, third and fourth) and geographical origins (south Spain, northeast Spain and Portugal), without prior maceration, using a fast and sensitive technique: headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The study aims to provide a complete characterization of the volatile compounds present in natural corks, which will enable the establishment of their sensory quality and traceability.