## 2 Analytical Strategies for Authentication and Quality Control
### Chromatographic and Hyphenated Techniques
Outside Europe, Brazil produces a grape mark spirit named Graspa with a production technology similar to that of Italian Grappa. To authenticate the geographical origin, comparative studies have been carried out in the past years [47] and more recently [48] between some of these spirit drinks and Italian Gr. In the most recent study [48], 28 compounds were determined by GC-FID and GC-MS to discriminate 15 samples of Italian Gr from 6 samples of Brazilian Graspa. The results of chemometric analysis using PCA and hierarchical cluster analysis (HCA) demonstrated the method's capability to discriminate between the two groups of grape mark spirits. Furthermore, analysis of variance (ANOVA) highlighted that methanol, diethyl succinate, isoamyl alcohol and propanol were the main discriminating compounds between the two sample groups. Although traditionally, Gr is not aged in wooden barrels, in the last two decades, Gr producers have started to age Gr spirits to meet the demands of the world market. For this reason, studies comparing the composition of this distillate according to different aging techniques are of increasing interest. Some authors used the SPE-GC-MS technique to compare the profile of volatiles present in Gr aged in oak casks with that present in Gr aged in cherry casks [49]. In that study, the effects of grape variety (Cabernet Sauvignon/Merlot blend and Prosecco) and ethanol content (55% and 68% \(v/v\)) on the overall volatile profile were also considered. The results showed that Gr aged in oak barrels was ten times richer in volatile substances than Gr aged in cherry barrels and that the compounds most affected were coniferaldehyde, syringaldehyde, vanillin, eugenol and guaiaicol derivatives. Furthermore, both ethanol content and grape variety influenced the extraction of volatiles from wood, with higher contents found for the Prosecco variety with 55% \(v/v\) ethanol. There is no legal obligation for producers to declare the wood seasoning conditions on the label, although they sometimes choose to claim this feature to differentiate their products from similar ones. It is, therefore, important to develop useful methods for verifying the declared seasoning protocols. In this regard, very recently [50], ionic chromatography (for the determination of organic acids) and GC-FID (for the determination of volatile compounds) coupled with chemometric tools have been used to characterize Brandy de Jerez aged in sherry casks seasoned for 0, 3, 6, 12, 18 and 60 months with different sherry wines. The study showed that the factors that mostly influenced the composition of organic acids and volatile substances of the brandies under investigation were the characteristics of the sherry wines used for barrel seasoning and the duration of seasoning. Similarly, ionic chromatography for the determination of short-chain organic acids [51] and ultra-high-performance liquid chromatography coupled with a photodiode array detector (UHPLC-PDA) to quantify polyphenols and furfurals [52] were used by other authors [53] to differentiate brandies of Jerez according to seasoning and aging time. Apart from the identification and quantification of marker compounds in spirit samples, other studies use the so-called \"fingerprinting\" approach, in which the overall analytical signal of the samples is acquired and analyzed with multivariate statistical techniques, which allow the different fingerprints to be clustered into distinct groups or categories. This approach, frequently used in food authentication [54], has been employed in two recent works to discriminate brandies according to different production processes. In the first study [55], the phenolic fingerprint determined by UHPLC-PDA and analyzed by chemometrics was used to differentiate brandies according to oak type, toasting degree and aging time. In the second work [56], the GC-FID technique was used to obtain the fingerprints of the main volatile fraction (corresponding to aldehydes, higher alcohols and major esters) of a series of brandies of Jerez aged 14 and 28 months.