# Spectroscopic Techniques Application for Wine and Wine Byproduct Authentication
## 2 Food Spectral Print Approaches
### Raman  
Raman spectroscopy is a vibrational spectroscopic technique that provides valuable insights into the chemical composition of a substance. It operates through inelastic scattering, allowing for the detection of vibrations associated with specific chemical functional groups within a sample molecule. This property makes Raman spectroscopy highly effective for molecular fingerprinting. The technique offers high specificity, with distinct, non-overlapping peaks, and is particularly well-suited for analyzing liquid samples. Since Raman signals are inherently weak and do not interfere with analysis, Raman spectroscopy is ideal for examining high-water-content matrices such as wine [105]. As a green, non-destructive method, it enables rapid analysis and requires minimal sample preparation, making it particularly useful for authenticating wine and other aqueous samples [106; 107; 108; 109].  
A Raman spectrometer generates a spectrum that provides key molecular information, including vibration frequencies, peak position shifts, peak width, spectral intensity, half-width at half-height, and the debiasing ratio. Because Raman spectroscopy is highly sensitive to molecular bonding and structural variations, each molecule or sample exhibits a unique \"fingerprint\". Various Raman techniques, such as dispersive Raman spectroscopy (DRS), Fourier transform Raman spectroscopy (FT-RS) [111], micro-confocal Raman spectroscopy (MCRS), spatially offset Raman spectroscopy (SORS) [75; 112], resonance Raman spectroscopy (RRS) [112], and surface-enhanced Raman spectroscopy (SERS) [113; 75; 114], are widely applied in food analysis. Figure 4 represents a schematic of the measurement principle in a Raman spectrometer, illustrating how it works. A laser light source illuminates the sample, causing the light to interact with the molecules. The inelastically scattered light is then separated into different wavelengths by a dispersive element. The detector analyzes the various wavelengths and their intensities, converting the data into the final spectrum.  
One significant advantage of Raman spectroscopy is its ability to be performed directly in aqueous environments and through glass containers, as both water and glass produce minimal interference in the Raman spectrum [115]. Their weak signals do not overlap with those of key food components, such as lipids [116], proteins [117], and carbohydrates [118], which exhibit high sensitivity and specificity.  
Due to its rich spectral information, Raman spectroscopy offers distinct advantages in verifying food authenticity [119]. The Raman scattering effect has been explored in  
Figure 4: A schematic of a Raman spectrometer measurement principle illustrates how the instrument operates.  
wine discrimination studies, particularly when combined with chemometric analysis, to distinguish wines from the protected designation of origin of Piemonte (Northwest Italy) based on grape variety, production area, and aging time [120]. Similarly, it has been successfully applied to differentiate between wines from Romania and France, concerning cultivar, geographical origin, and vintage [121].  
As mentioned earlier, spectroscopic techniques are particularly useful for analyzing various properties of wine, including its chemical composition, quality, aging potential, and even flavor profile. However, raw spectral data often contain noise, unwanted variations, and redundancies that must be addressed before meaningful analysis. Statistical techniques provide powerful tools for processing, modeling, and integrating spectroscopic data, enhancing their interpretability and predictive capabilities.