Determination of Nepsilon-(carboxymethyl)lysine in food systems by ultra performance liquid chromatography-mass spectrometry

We report the use of ultra pressure liquid chromatography (UPLC), coupled to a tandem mass spectrometer operated in multiple reaction monitoring mode to determine the advanced glycation endproduct, Nepsilon-(carboxymethyl)lysine (CML). The procedure was applied to acid hydrolyzates of protein isolated from a range of foods (milks processed at different temperatures, butter, cheese, infant formulae, bread, raw and cooked minced beef and olive oil). Highest levels of CML were determined in white bread crust (15.2 +/- 0.63 mmol/mol Lys), wholemeal bread crust (13.1 +/- 0.61 mmol/mol Lys) and evaporated full-fat milk (4.86 +/- 0.77 mmol/mol Lys). Lowest levels of CML were measured in raw minced beef beef (0.03 +/- 002 mmol/mol Lys), raw full-fat cow's milk (0.08 +/- 0.03 mmol/mol Lys) and pasteurized skimmed cow's milk (0.09 +/- 0.002 mmol/mol Lys). CML could not be detected in olive oil.