**5.2 Main analytical techniques that can be used for the discrimination and evaluation of product quality**

The challenge of explaining the sensory differences described previously from a chemical point of view, is not easy. Considerable works have addressed the chemical characterization of wines aged with alternative products. However, only some of these studies have directly compared the composition of a barrel-aged wine and that of a wine in contact with wood oak fragments [45, 87–91]. Nevertheless, it is equally clear that, because of the need of control for consumer protection and quality assessment, it is essential to develop methods of investigation that allow distinguishing wines arising from barrel aging from those that used alternative woods. To our knowledge, the main techniques that have been used so far for this purpose are: (i) methods examining differences in phenolic composition (based on High Performance Liquid Chromatography (HPLC) or on classical phenolics determination) and color analyses; (ii) chromatographic techniques investigating.

Variances in xylovolatiles and other Volatile Organic Compounds (VOCs), mostly Gas chromatography (GC) and GC–Mass Spectrometry-based (GC-MS); (iii) infrared spectroscopy (IR) for discriminating wines through an overall chemometric approach, mainly through NIR (near infrared) and MIR (Mid infrared) spectroscopy; and (iv) Nuclear Magnetic Resonance (NMR)-based methods. Most of the following research work is based on studies carried out by coupling 2 or more of the abovementioned techniques, and treating the composite data sets through multivariate statistical analyses [5].
