## 4 Vibrational Spectroscopic Techniques for Non-Invasive Food Authentication
### Raman Spectroscopy for Non-Invasive Food Authentication
Despite this challenge, RRS has been successfully used for the characterization of microorganisms in various food products, aiding in the detection and analysis of microbial contamination [104]. These advanced Raman techniques are helping to push the boundaries of food analysis, offering powerful, non-destructive tools for improving food quality control, authenticity testing, and contamination detection. SERS is a technique that merges Raman spectroscopy with nanotechnology by utilizing metallic nanosubstrates to significantly enhance the sensitivity and capabilities of conventional Raman analysis. By employing materials such as gold or silver nanoparticles, SERS can amplify the Raman signal of a molecule adsorbed on the surface of these metals, leading to signal enhancements by factors of 5 to 6 orders of magnitude compared to the same molecule in its bulk form. For example, with gold nanosubstrates, the enhancement factor can exceed three orders of magnitude. This dramatic improvement in sensitivity makes SERS a powerful analytical tool for the characterization of a wide array of inorganic substances and biologically relevant compounds. As a result, SERS is becoming an increasingly popular technique for chemical analysis in various fields, including food science, where it is used for detecting contaminants and adulterants and analyzing food composition [105]. The ability to obtain high sensitivity with minimal sample preparation makes SERS particularly valuable for food quality control and authenticity testing. Raman spectroscopy is a highly effective tool for analyzing muscle foods, offering detailed structural information about key components such as proteins, water, and lipids. This capability has made it a valuable technique in the food industry, especially for detecting meat authenticity and assessing quality. For instance, it has been successfully used to predict sensory attributes like texture, tenderness, and juiciness in beef samples [106, 107, 108]. Additionally, Raman spectroscopy has been applied to determine the fatty acid composition of unextracted adipose tissue in various meat types and to assess the fat content in fish muscle [109]. The technique also has applications in monitoring changes in muscle protein during storage, such as in detecting muscle fiber tissue [110]. Furthermore, Raman spectroscopy can be used to track protein structure in muscle foods, which is crucial for understanding the textural qualities of meat [111]. Raman spectroscopy is not just limited to evaluating chemical and physical properties; it also has the ability to detect microbial spoilage in meat [112], offering significant advantages for food safety. A notable application in food authenticity is its use in detecting beef adulteration with horsemeat. There has been a steady growth in research output of technological adoption for NIR, FTIR, and Raman spectroscopy in food authentication from 2010 to 2024, with significant acceleration post-2018, particularly in portable and in-field devices. Table 2 summarizes the key advantages, limitations, and common applications of each technique. Recent advances in wearable spectroscopic devices and AI have significantly expanded the scope of food authentication. Wearable or handheld sensors enable real-time, on-site \begin{table}
\begin{tabular}{c c c c} \hline
**Feature** & **NIR** & **FTIR** & **Raman** \\ \hline Water Interference & Moderate & High & Low \\ Sample Prep & Minimal & Minimal–Moderate & Minimal \\ Sensitivity & Medium & High & Very High (esp. SERS) \\ Instrument Cost & Medium & Medium & High \\ Portability & High & Medium & Increasing \\ Major Applications & Bulk analysis and & Molecular fingerprinting & Protein/lipid analysis and \\  & adulteration & and sugar detection & contaminant detection \\ \hline \end{tabular}
\end{table} 
Table 2: Comparative summary of NIR, FTIR, and Raman spectroscopy. analysis, providing rapid decision-making tools for field or retail applications.