title: Detection of sheep and goat milk adulterations by direct MALDI-TOF MS analysis of milk tryptic digests.
abstract: In dairy field, one of the most common frauds is the adulteration of higher value types of milk (sheep's and goat's) with milk of lower value (cow's milk). This illegal practice has an economic advantage for milk producers and poses a threat for consumers' health because of the presence of hidden allergens as, for example, cow milk proteins, in particular, α(s1)-casein and β-lactoglobulin. The urgent need of sensitive techniques to detect this kind of fraud brought to the development of chromatographic, immunoenzymatic, electrophoretic and mass spectrometric assays. In the current work, we present a fast, reproducible and sensitive method based on the direct matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) MS analysis of milk tryptic digests for the detection of milk adulteration by evaluating specie-specific markers in the peptide profiles. Several pure raw and commercial milk samples and binary mixtures containing cows' and goats', cows' and sheep's and goats' and sheep's milk (concentrations of each milk varied from 0% to 100%) were prepared, and tryptic digests were analyzed by MALDI-TOF MS. The use of the new MALDI matrix α-cyano-4-chlorocinnamic acid allowed to detect cow and goat milk peptide markers up to 5% level of adulteration. Finally, from preliminary data, it seems that the strategy could be successfully applied also to detect similar adulterations in cheese samples.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, via Orabona 4, 70126, Bari, Italy. calvano@chimica.uniba.it
authors.forename: Cosima Damiana
authors.initials: CD
authors.lastname: Calvano
authors.forename: Cristina
authors.initials: C
authors.lastname: De Ceglie
authors.forename: Antonio
authors.initials: A
authors.lastname: Monopoli
authors.forename: Carlo Giorgio
authors.initials: CG
authors.lastname: Zambonin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002611:Cheese / Q000032:analysis; D005504:Food Analysis / Q000379:methods; D005506:Food Contamination / Q000032:analysis*; D006041:Goats; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D012756:Sheep; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D014357:Trypsin / Q000378:metabolism
chemical_list: D008894:Milk Proteins; D010446:Peptide Fragments; D014357:Trypsin