Differences in peptide oxidation between muscles in 12 months Spanish dry-cured ham.

Oxidative modifications of proteins and peptides can negatively affect nutritional, sensory and quality characteristics of dry-cured hams. The aim of this study was to use a peptidomics strategy for the identification and relative quantification of oxidised peptides in two different muscles, the external Semimembranosus (SM) and the internal Biceps femoris (BF), from dry-cured hams of 12 months of curing. The analysis by nanoliquid chromatography-tandem mass spectrometry identified peptides showing oxidation at different amino acid residues such as methionine, cysteine, histidine, tryptophan, and phenylalanine. The highest percentages of oxidised peptides identified in SM and BF muscles were from pyruvate kinase protein (16.7 and 28.6%, respectively). The relative quantitation of oxidised peptides using mass spectrometry in tandem label-free methodology evidenced significant differences between muscles, with myosin and troponin fragments as main responsible peptides for the clustering of data. The existing differences between BF and SM peptides were confirmed using MALDI imaging mass spectrometry technique. The obtained results suggest that differences in physicochemical characteristics such as water and salt contents between SM and BF muscles could affect the quantity of peptide oxidation. This peptidomics approach has allowed to analyse differences in peptide oxidation between dry-cured ham muscles as well as to improve the knowledge about the oxidative processes that occur in dry-cured hams.