# Spectroscopic Techniques Application for Wine and Wine Byproduct Authentication
## 2 Food Spectral Print Approaches  
### UV-Vis Spectroscopy  
UV-Vis spectroscopy is a widely used analytical technique in the wine industry for authenticating and characterizing wines and wine byproducts. This method is valued for its simplicity, cost-effectiveness, and ability to provide rapid results, making it an attractive option for quality control and fraud prevention in the wine sector. \begin{table}
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**Spectroscopic Technique** & **Application** & **Key Insights** \\ \hline NMR & Wine ingredient quantification and metabolomic fingerprinting & \({}^{1}\)H NMR spectroscopy is gaining attention for its simplicity and speed, although it lacks official recognition. It allows for both targeted and non-targeted analysis, providing a comprehensive profile of wine samples [19; 20]. Combined with chemometric analysis, these techniques effectively classify wines by grape variety and vintage year. UV-Vis is more effective for varietal discrimination, while FT-IR excels in vintage classification [1]. \\ Fluorescence Spectroscopy (A-TEEM) & Geographical and varietal authentication & A-TEEM, combined with machine learning, achieves high accuracy in classifying wines by variety and origin. It also effectively predicts phenolic compound concentrations [4; 21; 22]. These techniques analyze packaging labels to differentiate genuine bottles from counterfeit ones, offering a non-destructive authentication method [23]. \\ Data Fusion Approaches & PDO wine vinegar classification & Combining multiple spectroscopic techniques (MIR, NIR, EEM, \({}^{1}\)H-NMR) enhances classification accuracy and provides a comprehensive analysis of wine vinegar [24]. \\ \hline \end{tabular}
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Table 1: Applications and key insights of the most commonly used spectroscopic techniques. UV-Vis spectroscopy involves the absorption of electromagnetic radiation by molecules, leading to electronic transitions. The technique measures the amount of light a sample absorbs at different wavelengths, which is related to the concentration and nature of the absorbing species. It operates on the principle that molecules absorb light at specific wavelengths, depending on their electronic structure [26; 27]. The apparatus (Figure 1) typically consists of a light source, a monochromator to select specific wavelengths, a sample holder, and a detector to measure the intensity of transmitted light. Indeed, a UV-Vis spectrophotometer is a device that measures the absorption of ultraviolet and visible light. It uses a light source, either a deuterium lamp for UV light (190-400 nm) or a tungsten-halogen lamp for visible light (400-800 nm). The light passes through a diffraction grating or prism, which separates it into different wavelengths. A slit then selects one specific wavelength to go through to the sample. The sample is placed in a cuvette made of quartz for UV light or glass or plastic for visible light. A photodetector, such as a photomultiplier tube or photodiode array, measures the amount of light that passes through or is absorbed by the sample. The device calculates absorbance (A) using the Lambert-Beer Law (explained below). Finally, the spectrophotometer creates an absorption spectrum that shows absorbance versus wavelength. This spectrum helps to identify and measure the substances in the sample. These components are crucial for ensuring accurate measurements. These components are crucial for ensuring accurate measurements [27], as shown in Figure 1.  
The technique is based on the Lambert-Beer Law (Equation (1)), which relates absorbance to concentration and path length. However, users must be aware of its limitations and potential sources of errors in routine analysis [28]. \[A=log\left(\frac{I0}{I}\right) \tag{1}\]  
where \(I0\) is the intensity of incident light and \(I\) is the intensity of the transmitted light. A critical area of application is wine authentication.