Proteome changes in bovine longissimus thoracis muscle during the early postmortem storage period.

Postmortem changes in protein composition up to 24 h in bovine longissimus thoracis muscle were investigated by two-dimensional gel electrophoresis and MALDI-TOF MS/MS. A total of 47 spots were significantly changed the first 24 h postmortem. The 39 identified proteins can be divided into five groups: metabolic enzymes, defense and stress proteins, structural proteins, proteolytic enzymes, and unclassified proteins. The identified metabolic enzymes are all associated with ATP-generating pathways, either the glycolytic pathway or energy metabolism. In addition, several defense and stress proteins were changed in abundance in this study. These findings contribute to a better understanding of the biochemical processes during postmortem storage of meat.

Variation in the response to manipulation of post-mortem glycolysis in beef muscles by low-voltage electrical stimulation and conditioning temperature.

The aim of this study was to investigate how manipulation of glycolytic rate by post-mortem processing conditions influences quality of aged beef of two bovine muscles of different physiological character, longissimus dorsi (LD) and adductor (AD). Post-mortem glycolysis was manipulated by low-voltage electrical stimulation (LV-ES) of half carcasses and by chilling rate of the muscles. Multivariate statistical analysis was used to visualise the data, while ANOVA was used to identify significant effects and interactions. As expected there was a significant effect of LV-ES on the pH decline in the first hours post-mortem in both muscles. Moreover, significant effects of LV-ES on WB shear force measured 2 and 8 days after slaughter were observed for LD at both chilling temperatures, while for AD no effect on WB shear force was observed. Furthermore, the results revealed a large individual variation in the response of LV-ES on both pH decline and WB shear force, and this variation did not always correlate for the two responses. Some animals showed no response of LV-ES on pH decline, but still had an improved WB shear force, and vice versa. The results from this study indicate that there probably are other mechanisms than accelerated pH decline and prevention of cold-shortening, by which LV-ES can affect meat tenderness.

Changes in enzymes associated with energy metabolism during the early post mortem period in longissimus thoracis bovine muscle analyzed by proteomics.

Changes in metabolic protein levels in biopsies during the early post mortem period in the bovine longissimus thoracis muscle were investigated by 2-DE based proteome analyses. Nine NRF (Norwegian Red) dual purpose bulls were included in the study. Twenty-four proteins underwent changes between the two sampling times and were classified into two major groups: metabolic proteins and heat shock proteins. Of the metabolic proteins, 5 enzymes involved in the glycolytic pathway and the tricarboxylic acid (TCA) cycle, increased in intensities during the post mortem period. In addition, the NADP-dependent enzyme 3-hydroxyisobutyrate dehydrogenase, associated with the TCA cycle in muscle, was increased. This documents that an increased aerobic energy metabolism occurs immediately after slaughter, with the aim to replenish the ATP levels in the muscle.