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.

Proteomic Analysis of Complex Protein Samples by MALDI–TOF Mass Spectrometry

“…Sample pretreatment consists of a simple in-solution digestion step of the whole samples rendering the procedure suitable for routine analysis of both raw and processed foods. The method can be a useful tool to detect adulterations in both matrices [ 30 ]. The results obtained by the present method are in good agreement with those obtained by a standard but time-consuming approach, i.e., SDS-PAGE followed by in-gel digestion.…”

MALDI-TOF-MS Platform for Integrated Proteomic and Peptidomic Profiling of Milk Samples Allows Rapid Detection of Food Adulterations

“…For adulteration studies, binary mixtures of BM in WM, OM and GM counterparts, or IM in BM were prepared at 1, 2,5,10,15,20,30,40 and 50% v/v values. Three independent samples were prepared for each specific binary mixture.…”

Advanced Mass Spectrometry

“…Proteomic approach to detect powdered milk in fresh cow's milk [114] MALDI-TOF-TOF Proteins as targets of ferrous-catalyzed oxidation: identification of protein carbonyls [37] LC-TOF Evaluation of the immunostimulating activity of soybeans via the determination of the functional peptide soymetide [115] SELDI-TOF Effect of NaCl and sucrose tastants on protein composition of oral fluid [44] MALDI-TOF Hydrolysis of β-lactoglobulin by trypsin under acidic pH [116] UHPLC-TOF Quantification of Se-methylselenocysteine and its γ-glutamyl derivative from naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) [50] MALDI-TOF Detection of sheep and goat milk adulterations by direct MALDI-TOF-MS analysis of milk tryptic digests [117] CE-TOF Identification of bioactive peptides in hypoallergenic infant milk formulas [58] UHPLC-QqTOF Differentiation bovine and porcine gelatins in food products [118] [120]…”