# MALDI-TOF Mass Spectrometry Applications for Food Fraud Detection
## 2 MALDI Applications
### Milk and Dairy Products
The MALDI mass spectra profiles of \(\alpha\)-lactalbumin and \(\beta\)-lactoglobulin were used to detect the fraudulent addition of goat or cow milk in donkey milk [40] in a protocol developed for routine analysis and potentially extendable to other milk species. Detection limits for the analysis of defatted milk samples were in the range 0.5-2.0%, comparable to those obtainable with traditional complex approaches. Despite the typical MALDI quantitative issues, the measured values were in good agreement with the actual composition of the analyzed mixtures. Another study [41] investigated donkey and goat milk adulteration by cow and sheep milk using MALDI in combination with unsupervised hierarchical clustering, principal component (PCA), and Pearson's correlation, focusing on the mass spectra profiles in the \(m/z\) mass range 2000-25,000 Da. The approach was shown to be rapid, robust, and sensitive, with detection limits of 0.5%. The adulteration of fresh milk by reconstituted milk and the selling of reconstituted milk as fresh product is economically advantageous when either a surplus of milk powder exists, or when the importation of dried milk powder is subsidized. Moreover, the addition of powdered derivatives is difficult to detect because the adulterant materials have almost the same chemical composition of liquid milk. Specific peptide markers, attributable to modified whey proteins and/or caseins, formed by thermal degradation during milk powder production, were identified and used to detect the presence of powdered milk in liquid milk samples [42]. whey and casein fractions of milk samples were directly digested in solution and analyzed by MALDI using \(\alpha\)-cyano-4-chlorocinamic acid as a matrix,which enhanced the detection of more acid peptides. The approach was able to detect the peptides diagnostic for the presence of powder in liquid milk even at a 1% level. The results were in good agreement with those obtained with a reliable but time-consuming 2D gel approach. On the contrary, milk powder itself could be the object of adulteration when non-milk fat such as vegetable oils and fats are added. [PERSON] and co-workers [43] successfully developed a MALDI-qTOF method for the fast individuation of non-milk fats and oils in milk powder. Samples were subjected to a simple n-hexane extraction prior to MS analysis, which provided rapid and unambiguous profiles of the triacylglycerlecrols (TAGs) composition capable to characterize the adulterant and estimate the adulteration level. Other MALDI applications on the detection of frauds were focused on different kind of mills and adulterations, as well as to the analysis of cheese samples. [PERSON] at al. [44] compared the principal proteins in bovine, caprine, buffalo, equine, and camel milk, finding interesting differences between the species that could be used to identify sources of hypoallergenic alternatives to bovine milk and detect adulteration of milk samples and derived products. A proteomic approach for the MALDI-TOF analysis of commercial bovine milk, based on in-solution digestion of the whole samples, was also suggested [45] for the routine analysis of raw and processed foods and to detect adulterations. Due to similar properties to bovine milk, soya milk is added to bovine milk for revenue maximization. In a recent work, England and colleagues [46] used MALDI to develop a solventless, sensitive, and cost-effective method for the discrimination of bovine milk from soya and coconut milk as well as for the individuation of milk adulteration. Samples were simply diluted in water, combined with the matrix, and subjected to instrumental analysis, which allowed to obtain unique lipid profiles (mainly phosphatidylcholine and TAGs). [PERSON] at al. reported a qualitative method to check the authenticity of a typical Brazilian cheese using \(\beta\)-lactoglobulin as an adulteration marker [47], showing good precision and sensitivity (7 mg/g). The procedure involved SDS-PAGE and in-gel trypsin digestion followed by MALDI analysis.