## 2 Analytical Strategies for Authentication and Quality Control
### Spectroscopic Methods
#### 2.1.3 Fluorescence Spectroscopy  
Fluorescence spectroscopy is a technique that is gaining importance in the analysis of beverages due to its sensitivity and selectivity. Fluorescence spectra of beverages generally consist of broad, overlapping fluorescent bands containing chemical and physical information about different components of the sample. WB GIs contain several fluorophores, but there are relatively few recent works about the use of fluorescence on these matrices, most of which use a fluorescence excitation spectrum recorded at one emission wavelength [33; 34]. A technique that provides more detailed information on fluorescent species is excitation-emission matrix (EEM) fluorescence spectroscopy. Using this technique, all fluorophores within the sample are excited simultaneously over the explored wavelength range, allowing the collection of all excitation and emission spectra and obtaining the total fluorescence spectrum of the sample. This analytical approach, with front-face and right-angled arrangements, combined with specific chemometric calibration tools, namely parallel factor analysis PARAFAC multiple linear regression (MLR) and PARAFAC-PLS, was applied to quantify mixed wine spirits in some adulterated brandy blends [35]. The most promising results were obtained using right-angled geometry and PARAFAC-PLS. This approach allowed the determination of the presence of wine spirit mixed in the adulterated brandy with a coefficient of determination of 0.995% at a level below 1.9% (\(v/v\)). The same approach was used in another work [36] to quantify the amount of water and ethyl and methyl alcohols in adulterated brandy mixtures, obtaining root mean square prediction errors < 0.24% and coefficients of determination in prediction > 0.993. Another technique frequently applied to analyze spirit drinks is synchronous fluorescence spectroscopy (SFS). It is based on the simultaneous scanning of excitation and emission signals with a fixed wavelength range with the aim of obtaining more resolved spectra than those coming from conventional fluorescence spectroscopy [37]. Some authors compared SFS spectra with emission spectra (both processed by PCA) and with EEM spectra (processed by unfold PCA and PARAFAC) to authenticate 44 brandy samples based on their geographical origin [38]. The SFS method performed at two wavelength ranges (20 and 60 nm) on diluted samples showed the best performance with 95.5% correct classification. Innovative techniques such as SFS, which appear to have a high potential for brandy authentication, highlight the importance of accurate data analysis in order to have good discriminating power. In Table 1, an overview of the main features of the cited studies on spectroscopic techniques for the authentication of Gr and WB is reported. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Samples** & **Discriminating Parameters** & **Method of Analysis** & **Data Analysis** & **Results** & **References** \\ \hline \hline \multirow{6}{*}{Grape maze spirits, wine sprits and brandes} & Screening analysis for & & & Accuracy values: & \\  & alcoholic strength and & FTIR-ATR & & methanol (\({}^{2}\) = 99.4\%; RPD = 12\%; \\  & sprits and brandes & content of & spectroscopy in the MIR & PLS & alcoholic strength (\(t^{2}\) = 97.2\%; RPD = 6.01; acetaldehyde (\(t^{2}\) = 982.5\%; RPD = 7.5)) and fused alcohols & [16] \\  & methanol, acetaldehyde and & region (4000–400 cm\({}^{-1}\)) & & 7.5\%) and fused alcohols (\(t^{2}\) from 97.4 to 94.1\%; RPD from 62 to 4.1). & \\ \hline \multirow{6}{*}{Wine sprits (5 not aged, 2 aged by) and 6 aged for a long time) + 3 commercial brandes} & \multirow{2}{*}{Aging duration} & NIR spectroscopy & \multirow{2}{*}{PCA, PLS, LDA} & Accuracy values: & \\  & & (904-935 nm and 1400–1699 nm).