# Spectroscopic Techniques Application for Wine and Wine Byproduct Authentication
## 2 Food Spectral Print Approaches
### UV-Vis Spectroscopy
UV-Vis spectroscopy, often combined with chemometric techniques, effectively distinguishes between grape varieties and vintage years. Studies have shown that UV-Vis spectroscopy can outperform methods like FT-IR in varietal classification, while FT-IR may be more effective for discriminating vintage years [1; 29]. This technique also authenticates wine vinegas, distinguishing between different production methods and protected designations of origin (PDOs) [24; 30]. [PERSON] et al. [24] investigated the application of hierarchical classification models and reliability estimation by bootstrapping for the authentication and discrimination of wine vinegar  
Figure 1: Schematic representation of a UV–Vis spectrophotometer composition and operating mode. samples using UV-Vis spectroscopy. The study demonstrated the effectiveness of UV-Vis spectroscopy in differentiating wine viregars. A hierarchical classification model utilizing PLS-DA, soft independent modeling of class analogy (SIMCA), and bootstrapping was developed to distinguish between \"aged\" and \"non-aged\" wine viregars, as well as between PDO and non-PDO wines and various aging categories within PDOs. The results indicated that the UV region around 300 nm and the visible range between 500 and 600 nm effectively distinguished the most aged vinegars (\"Reserva\" category). In comparison, the least-aged samples (\"Crianza\" and \"Solera\" categories) were better explained by wavelengths in the range of 290 nm and between 350 and 500 nm. Phenolic compounds significantly influence the sensory attributes of wine, such as color and flavor. UV-Vis spectroscopy, in conjunction with chemometrics, is employed to monitor the phenolic composition during winemaking. It is particularly effective in determining anthocyanin concentration and evolution, which is crucial for assessing wine quality [31, 32]. [PERSON] et al. [32] analyzed the tannin and anthocyanin content of ninety-two wines from various vintages, varieties, and regions. Tannin concentration was measured using protein and polysaccharide precipitation and the Bate-Smith assay, while free anthocyanin was assessed through bisulfite bleaching. Additional methods included HPLC/UV-Vis for determining the molecular concentration of anthocyanin and dual-spectrum collection using both UV-Vis and FTIR. Statistical analysis using partial least squares (PLS) regression revealed significant correlations, with most parameters exhibiting coefficients of determination exceeding 0.7. FTIR proved more robust for predicting tannin concentration, while UV-Vis was more effective for anthocyanins. Combining both spectral methods improved the results, especially when incorporating visible wavelengths, highlighting the importance of the visible spectrum for estimating anthocyanin parameters. The technique can also quantify polyphenolic compounds in red wines, such as catechin and quercetin [33]. The primary advantages of UV-Vis spectroscopy include its rapid analysis capability, non-destructive nature, and low operational costs. It is suitable for routine analysis in the wine industry, providing a quick method for composition, authentication, and traceability [34]. However, the technique's effectiveness can be limited by the complexity of wine matrices and the need for sophisticated data analysis methods to interpret the results [34, 35, 36] accurately. The development of software tools like VinegarScan (Version 3.0), which utilizes UV-Vis spectra for quality control, highlights the potential for integrating this technique with portable devices for on-site analysis. This could enhance the ability of control bodies to prevent fraud and ensure product authenticity in the wine industry [30]. Future research may focus on improving the robustness and accuracy of UV-Vis spectroscopy models, potentially by combining them with other spectroscopic methods [32]. UV-Vis spectroscopy has been applied to analyze Chinese rice wines from four regions: Zhejiang, Jiangsu, Shanghai, and Fujian. [PERSON] et al.