## 2 Food Fingerprinting and Vibrational Spectroscopy Techniques  
Analytical methods that generate extensive, nonselective data for food characterization or authentication are commonly referred to as \"fingerprinting\" techniques; this broad category includes a variety of analytical approaches [8; 9; 24]. Terms such as \"metabolite profiling\", which emphasizes specific metabolites or molecular components; \"metabolomic profiling\"; and \"infrared fingerprinting\" have been introduced by various researchers to describe related concepts. Fundamentally, a food fingerprint refers to a distinctive set of molecular indicators ranging from specific substances to broader chemical traits that collectively characterize the unique physicochemical and functional profile of a given food item. This framework offers a robust approach to identifying, categorizing, and tracing food ingredients and products with precision. Ultimately, effectively tackling the complexities of food fingerprinting and enhancing authentication methodologies rely heavily on the ability to detect and characterize either individual molecular indicators or comprehensive marker profiles within the food matrix. Vibrational spectroscopy encompasses several techniques, including IR spectroscopy in both the NIR and MIR regions, as well as Raman spectroscopy. A unifying characteristic of these methods is their capacity to probe molecular structures and detect specific molecular species by analyzing the vibrational states of individual molecules or molecular groups; they capture the vibrational states of individual molecules or groups of molecules [23; 25; 26; 27; 28; 29]. Nonetheless, it is essential to recognize that these techniques may exhibit varying sensitivity to different vibrational modes and bond types within a molecule. Consequently, integrating multiple vibrational spectroscopy methods can provide complementary insights, offering a more comprehensive understanding of the composition and characteristics of food samples. Recent developments in Fourier transform instruments have resulted in advanced devices capable of analyzing a wide range of molecules in different forms, including solutions, powders, and even complex matrices such as food. A significant breakthrough has been the integration of attenuated total reflectance (ATR) modules with Fourier infrared instruments, which has notably improved their analytical performance. The growing number of applications using ATR-MIR technology highlights its effectiveness for food analysis. ATR has proven to be a valuable alternative for food sample analysis using MIR spectroscopy, providing a more efficient method. In ATR spectroscopy, the incident light is introduced into a high-refractive-index crystal, where it reflects internally at the crystal-sample interface. A portion of the evanescent wave extends a short distance beyond the surface into the sample, and if the sample is properly in contact, it selectively absorbs energy at characteristic wavenumbers, resulting in specific energy attenuation corresponding to molecular vibrations [20]. The penetration depth is influenced by factors such as the wavenumber, the refractive index of the crystal, and the incident radiation angle. Key benefits of ATR include the need for little or no sample preparation and its versatility in analyzing various food forms, including liquids, gels, solids, and powders [30]. However, when analyzing powders and solid samples, it is critical to ensure proper contact between the sample and the ATR crystal surface to obtain accurate results. NIR spectroscopy is one of the most widely used techniques in food analysis. It works by measuring the absorption of energy from chemical bonds found in functional groups like C-H, O-H, N-H, and C=O, which are directly related to the chemical makeup and structural properties of food products [29; 31; 32].