Influence of ultimate pH (pHu) on the occurrence of defective meats known as dark, firm, and dry (DFD) meats has been studied through a proteomic approach at early post-mortem times. The myofibrillar sub-proteome of longissimus thoracis et lumborum muscle from twelve loin samples from Asturiana de los Valles x Friesian yearling bulls, previously classified into two groups of six samples according to their pH values (normal, pHu < 6.0 and high, pHu ≥ 6.0), is analyzed at 24 h post-mortem. Fractionation/enrichment of muscle samples is carried out by combining OFFGEL fractionation in the pH range 4-7 followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the retrieved liquid fractions. Four protein bands satisfactorily discriminate between meat samples with normal and high pHu. These bands are quantified by image analysis, and further identified by liquid chromatography-mass spectrometry as desmin, pyruvate kinase, myosin light chain, and myosin heavy chain-1 and -2. Coupling OFFGEL and SDS-PAGE separation with MS provides detailed and reproducible myofibrillar protein profiles enabling comparison among the sample groups assayed. This makes feasible to identify biomarkers capable to better understand pre-slaughter stress condition susceptible to give DFD meats with high pHu values.
Keywords: LC-MS; OFFGEL fractionation; pre-slaughter stress; sodium dodecyl sulfate polyacrylamide gel electrophoresis; ultimate pH.
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