Investigation of Volatiles in Cork Samples Using Chromatographic Data and the Superposing Significant Interaction Rules (SSIR)  
[PERSON]  
1 Institute of Computational Chemistry and Catalysis, University of Girona, 170 aldehydes [11; 12]. The composition of the volatile fraction, also referred to as the volatile signature, is an informative diagnostic tool for cork quality and sensory qualification. Analytical methods for the study of volatiles rely on gas chromatography with mass spectrometry detection (GC-MS). GC-MS data is combined with sensory evaluation and, in some cases, with olfactometric (GC-O) analysis [9; 13; 14]. The isolation of the compounds can be performed directly from the cork samples or from the aqueous macroates [10; 15; 16]. In the latter case, the procedure employed consists in the simulation of the interaction of stoppers with wine under specific maceration conditions and using water or ethanol:water mixtures as matrices [17]. For the preconcentration of volatile molecules, the most commonly used techniques are static headspace (SHS), multiple HS, dynamic HS, headspace sorptive extraction (HSSE), solid phase extraction (SPE) and solid phase microextraction (SPME) [9; 10; 11; 18; 19]. The ideal method should have a high capacity and high extraction efficiency, no saturation, moderate selectivity, be easy to automate and not be time-consuming. SPME has been extensively employed in the field of aroma analysis because of its advantages: easy automation, high preconcentration factor, and the possibility of selecting the most appropriate coating for the intended application [20]. In general, the chemical composition of the volatile signature is rather complex. A few volatiles in cork present specific odor descriptors and low odor thresholds. The compound 2,4,6-trichloranisole (TCA) is undoubtedly the one that has been more extensively studied [18; 21], for two main reasons: firstly, it is responsible for the musty, or moldy, aroma, a negative sensory attribute that can be transferred to the wine; and secondly, TCA bears an extremely low sensory threshold, at around 1 ng L\({}^{-1}\) in water [21]. Other compounds, for example 2,4,6-tribromoanisole, 1-octen-3-one, geosmin, methylisoborneol, 2,3-dimethyl-5-methoxypyrazine and guaiacol, have also been described as contributing to the musty/moldy aroma in corks, but they are rarely found in cork macroates, with the exception of guaiacol [10; 22]. Although some of these compounds are endogenous to cork, contamination from external sources has been described, especially in the case of chlorophenols, which were extensively used as pesticides. The transformation of chlorophenols into chloroanisoles as a detoxification mechanism has been demonstrated [23]. The presence of TCA in cork stoppers constitutes one of the most important problems that the cork industry faces, since it causes significant economic losses and can damage the reputation of a cellar. Cork industries are continuously improving their production processes by applying different treatments to cork material to remove odorous compounds, seeking the inertness required in the fabrication of wine closures and, very particularly, the elimination of TCA. Some examples are the ROSA technology developed by the AMORIM cork company, which is based on the use of a distillation process with water steam [24; 25], different improved washing procedures, extraction using supercritical carbon dioxide, and the application of different types of radiation or electron beam irradiation [26]. [PERSON] et al. [27] have used hydrogen peroxide as an oxidant catalyzed by molybdate ions in alkaline conditions for the efficient destruction of TCA and pentachloroanisole. [PERSON] et al. [28] recommend ozone and/or sterilizing gases, such as steam, via the sequential application of pulsed vacuum-pressure cycles. The most common industrial treatments include temperature and humidity cycles, although the precise characteristics and experimental conditions are not in the public domain.