# MALDI-TOF Mass Spectrometry Applications for Food Fraud Detection
## 2 MALDI Applications
### Milk and Dairy Products
The applicability to real samples was demonstrated by the analysis of 42 commercial samples, 18 of which were found to be adulterated. Direct Imprinting in Glass Surface Mass Spectrometry (DIGS-MS) for qualitative cheese analysis in a MALDI instrument was also successfully used [48] to identify complex lipids to be used as quality and/or adulteration marker in different cheese samples. The integration of analytical and statistical data could also be employed for the control of productive stages. In another recent work [49], [PERSON] and co-workers developed an original method to identify the dairy animal species of mozzarella and white brined cheese by MALDI-TOF in combination with direct protein extraction without tryptic digestion and a small in-house reference spectra database. Some further MALDI works were oriented towards the quality evaluation of milk and dairy products. The selective extraction of phospholipids from dairy products such as milk, chocolate milk, and butter by micro-solid phase extraction (\(\mu\)-SPE), based on homemade titanium dioxide (TiO\({}_{2}\)) microcolumns, followed by MALDI-TOF MS, was developed by [PERSON] at al. [50]. Since \(\alpha\)-lactalbumin and \(\beta\)-lactoglobulin are among the main cow milk allergens, [PERSON] at al. [51] developed a sensitive quantitative method for their determination by immunoaffinity capillary electrophoresis, using magnetic beads functionalized with opportune antibodies, coupled to MALDI. A transient isotachophoresis preconcentration step allowed to obtain LOD values of 0.02 and 0.03 \(\mu\)g/mL for \(\beta\)-lactoglobulin and \(\alpha\)-lactalbumin, respectively, suitable for allergen detection. The method was then successfully tested on cow milk and fortified soy milk, proving the capability to determine the analytes at both high and low concentration levels. To identify and characterize oxidized and glycated phospholipids in heat-treated food, namely milk powders, pasteurized milk, ultra-high-temperature milk, and soy flour, an extraction protocol [52] was developed by means of a methanolic solution of 1,8-bis(dimethylamino) naphthalene (DMAN), used as both extraction medium and matrix for the successive MALDI detection, performed in negative ion mode. Thermally modified lipid products were first characterized by heating representative standards and eventually determined in real samples. MALDI-TOF, combined with C18-stage tip extraction, was also used [53] to rapidly obtain peptide profiles from different commercial milk products in view of the identification of possible changes induced by different heating regimens and storage conditions. Several peptide ions showed relative abundance variations following specific treatments, such as heating or proteolytic activity of enzymes during storage, suggesting their potential use as markers to draw information on milk types and freshness. A similar approach permitted [54] the generation of polypeptide profiles from buffalo milk samples subjected to different freezer storage times, to assess their freshness through the identification of specific markers. The statistical evaluation of data relevant to the analysis of several fresh and frozen samples allowed to identify 28 polypeptide markers of freezing storage originated from the breakdown of buffalo proteins, being \(\alpha\)-lactalbumin, \(\beta\)-lactoglobulin, \(\gamma\)2-, \(\gamma\)3-, and \(\gamma\)4-caseins, \(\beta\)-casein-derived phosphopeptides, and GLY-CAM1 phosphorylated peptides as the most significant components. Their progressive formation even in freezing conditions was attributed to an unknown protease stable at low temperatures. MALDI profiling of milk proteins, in combination with multivariate data analyses, also proved to be an optimal mean to discriminate between different milk types [55]. Protein fingerprints of mammalian (various species), human (at different lactation stages), and formula (different brands) mills were rapidly obtained, permitting to obtain key information on the matrices under study.