Proteomic analysis of yak Longissimus dorsi muscle by two-dimensional electrophoresis

The fat food group, especially butter, has so far been thought to have a high Nε-carboxymethyl-lysine (CML) content. However recent data have challenged this opinion. The objective of this article was to determine not only CML content but also that of 5-hydroxymethylfurfural (HMF) in raw and cooked butters. The first aim of this study was to verify the accuracy of the LC–MS/MS and LC–UV methods used for the quantification of CML and HMF. The tests on fortified butter samples showed recovery values of 72% for CML and 78% for HMF. The amounts of CML in raw and cooked butters were 0.25 ± 0.03 and 2.22 ± 0.56 μg/g, respectively. The level of HMF in cooked butters was 61 ± 40 μg/g. No CML was detected in clarified butter, and no HMF was detected in raw and clarified butters. The results indicate that the contribution of butter alone to the exposure to CML and HMF is very low.