# MALDI-TOF Mass Spectrometry Applications for Food Fraud Detection
###### Abstract  
Chemical analysis of food products relating to the detection of the most common frauds is a complex task due to the complexity of the matrices and the unknown nature of most processes. Moreover, frauds are becoming more and more sophisticated, making the development of reliable, rapid, cost-effective new analytical methods for food control even more pressing. Over the years, MALDI-TOF MS has demonstrated the potential to meet this need, also due to a series of undeniable intrinsic advantages including ease of use, fast data collection, and capability to obtain valuable information even from complex samples subjected to simple pre-treatment procedures. These features have been conveniently exploited in the field of food frauds in several matrices, including milk and dairy products, oils, fish and seafood, meat, fruit, vegetables, and a few other categories. The present review provides a comprehensive overview of the existing MALDI-based applications for food quality assessment and detection of adulterations. M +
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Footnote †: making the analysis even more complicated. Moreover, as technologies develop to detect deceptions, they become more sophisticated since fraudulent suppliers also adapt to finding new ways to circumvent the controls. Targeted and non-targeted analytical approaches are mainly used for food controls [5; 6; 7]. A targeted analysis, generally laborious and time-consuming, is based on the knowledge of the contaminants and focused on the detection of one or a few classes of compounds that represent the markers of the fraud. Since in most cases the type of fraud is unknown, a non-targeted analysis is often necessary. This approach relies on the fast instrumental acquisition of the chemical profile of the whole foodstuff sample, usually represented by spectra, which should provide a unique fingerprint as a reference for suspect samples, often with the help of chemometric data handling [8]. Spectroscopic techniques [5; 9; 10; 11; 12; 13; 14; 15; 16], namely nuclear magnetic resonance (NMR), near- and mid-infrared (NIR, MIR), Raman, ultraviolet-visible (UV-VIS), and X-ray fluorescence spectroscopy (XRF), have been largely used to successfully carry out non-targeted analysis. Different mass spectrometry (MS) techniques and ionization approaches, including matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF), electrospray (ESI), ambient mass spectrometry (AMS), and high-resolution mass spectrometry (HRMS), have been also widely employed for the same purpose [17; 18; 19; 20; 21; 22; 23], and their constant advances have enabled the development of numerous new methodologies for food quality and safety controls. Among them, MALDI-TOF represents an ideal option for fast, reliable, and accurate detection of food frauds due to some intrinsic characteristics such as ease of use and speed with which data can be collected even from complex samples. MALDI MS is based on the use of a pulsed laser beam that hits the sample, represented by co-crystals of the so-called \"matrix,\" present in a vast excess, and the analyte. The laser energy is absorbed by the matrix that vaporized carrying intact analyte molecules into the vapor phase. During this process, ions (mainly H\({}^{+}\) and Na\({}^{+}\)) are released by the matrix leading to the formation of charged analyte molecules. Moreover, anions can also be generated by abstracting H\({}^{+}\) or Na\({}^{+}\) from the analyte. After being accelerated in an electric field and passing a charged grid, the ions are separated in a TOF mass analyzer based on their \(m/z\) ratios (low mass ions arrive at the detector in a shorter time than high mass ions). A \"linear\" geometry of TOF analyzers is used for the analysis of high molecular weight molecules. Smaller molecules can be analyzed using a \"reflectron\" configuration able to balance the different initial velocities of the ions during the vaporization process, leading to a consistent improvement of resolution.