Muscle samples were taken from 31 pigs that were killed at a slaughterhouse and the drip loss exudates were collected by centrifugation. Portions taken one day postmortem were used to classify the meat into high, intermediate and low drip loss types, corresponding to losses of approximately 6, 4 and 2.5%, respectively.
The exudates collected on days 1, 3 and 7 postmortem were used for the proteome analysis. Proteins in meats from each class were compared in one experiment by 2D differential gel electrophoresis using fluorescent dyes. After image analysis of the gels, the protein spots which displayed different abundances across the phenotypes were selected for further investigation.
The samples were run again by 2D PAGE but this time on preparative gels and the protein spots were cut out for analysis by mass spectrometry. MALDI MS and MS/MS were carried out in the first instance and the peptide masses were searched against a porcine database. When spots could not be identified this way, the proteins were reanalysed by LC-tandem-MS.