# MALDI-TOF Mass Spectrometry Applications for Food Fraud Detection
## 2 MALDI Applications
### Fruits and Vegetables  
Intake of fruits and vegetables is highly recommended to promote good health due to their concentrations of bioactive compounds, including vitamins, minerals, antioxidants, and fiber. Indeed, the quality of these precious foods must be safeguarded and monitored using suitable analytical methods. MALDI-TOF was adopted for the development of many related applications. For instance, fruit skins were analyzed in two different works. It was demonstrated [99] that anthocyanins profiles of the berry skins of 23 red grape varieties can be easily and rapidly obtained by MALDI-TOF, enabling the identification of several varietal traits useful for the differentiation of authentic cultivars from hybrid ones on a molecular basis. Very recently, prorandomization profiles of different fruit skins were obtained [100] by MALDI-TOF coupled to multivariate analysis, which proved to be a useful tool to evaluate authenticity in mixtures of different prorandomlyadin. Three different MALDI studies were focused on the assessment of the authenticity of saffron, an expensive spice made from _Crocus sativus_ L. dried stigmas, which is often the object of frauds. MALDI MS imaging (MSI) was successfully applied [101] to the determination of different crocus species in saffron. This original approach was also compared to a traditional one, i.e., MALDI analysis after solvent extraction, and the relevant results were found in good agreement. The other two studies were both performed by [PERSON] at al., using MS or MS/MS as mass analyzer and curcumin as the non-isotopic isobaric internal standard. In the first one [102], powdered saffron was subjected to a one-step sample pre-treatment and subjected to MALDI analysis. Crocins C-1-C-6, flavonoids, unknown highly glycosylated crocins C-7, C-8, and C-9, and carotenoid-derived metabolites were detected. The method was shown to be fast, sensitive, reproducible, and suitable for routine quality controls, including the assessment of adulterations, as ascertained through the analysis of commercial samples. In the second one [103], picrocrocin was used as a saffron authenticity marker. Again, a rapid and simple method was developed, and very good quantitation parameters were obtained, with LOD (47.63 ppm) comparable or even lower than those obtained with other approaches. The high demand for cereals, a major part of the diet in most countries providing nutrients such as vitamins, minerals, carbohydrates, fats, and proteins, makes relevant frauds a severe global problem. Sequenom(r) MassARRAY() (Agena Bioscience, San Diego, CA, USA) MALDI-TOF MS, a reliable platform for detection and validation of single nucleotide polymorphisms (SNPs) for varietal analysis, was used to target specific genes in order to genotype and differentiate 35 barley varieties [104]. Information was drawn from the majority (33) of the tested loci (45), permitting the generation of a unique barcode of SNPs for each barley cultivar. This reliable and fast approach can potentially identify more than 150,000 SNPs per day, making the platform a suitable alternative for cereal varieta identification. [PERSON] at al. [105] used 2-DE followed by MALDI-TOF to compare the proteome extracted from barley malts of two selected cultivars, to find correlations between the protein content and malt qualities. Almost 700 total spots were detected; most were shared by the two cultivars, 377 of which were attributed to 192 proteins, mainly enzymes and enzyme inhibitors. The same research group performed another comparative study on green malts from two cultivars using two-dimensional fluorescent difference gel electrophoresis (2D-DIGE) [106]. Several metabolic proteins were identified by MS/MS and significant differences between cultivars were detected, suggesting potential applications for malt quality assessment. MALDI-TOF and two-dimensional difference gel electrophoresis (2D-DIGE) were also used by [PERSON] at al.