Milk hidden allergen quantification in bakery products by LC-MS/MS validated method.

A validated method based on LC-MS/MS and minimized sample preparation was set up to detect and quantify milk traces in bakery products. Two specific peptides from bovine ?-s1 casein were selected: the one showing the most intense transition was chosen for quantification (FFVAPFPEVFGK) while the second for confirmatory purposes (YLGYLEQLLR). Incurred material were prepared "in house" at eight levels of milk contamination: 1, 2, 5, 10, 15, 25, 75 and 150 mg of milk/Kg. Remarkable results were obtained for LOD (1.3 milk/Kg cookies), LOQ (4 mg milk/Kg cookies), intra-day repeatability (5-20% range) and inter-day repeatability (never exceeded 12%). In terms of recovery, values ranging from 20% to 26% were consistent with the method of calculation and with the choice of considering processed food (bakery products). Method applicability was then evaluated by testing commercial cookies with not exhaustive labelling. All samples tested were proven not to contain milk. These samples could be labelled as "milk-free", giving an opportunity both to consumers (especially milk allergy sufferers) and to producers to safeguard their interests, in terms of both health and legal requirements.