Abstract
In this paper, the protein changes during aging and the differences in the myofibrillar protein fraction at 1 h postmortem of pale, soft and exudative (PSE), and red, firm and non-exudative (RFN) pork longissimus thoracis (LT) were comparatively studied. The PSE and RFN groups were screened out based on the differences in their pH and lightness (L*) at 1 h, and their purge loss at 24 h postmortem. Based on the measured MFI, desmin degradation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, PSE meat presented more significant changes in the myofibrillar protein fraction compared to RFN meat during postmortem aging. Through liquid chromatograph-mass spectrometer/mass spectrometer (LC-MS/MS) analysis, a total of 172 differential proteins were identified, among which 151 were up-regulated and 21 were down-regulated in the PSE group. The differential proteins were muscle contraction, motor proteins, microfilaments, microtubules, glycolysis, glycogen metabolism, energy metabolism, molecular chaperones, transport, and enzyme proteins. The AMP activated protein kinase (AMPK) signaling pathway, HIF-1 signaling pathway, calcium signaling pathway, and PI3K-Akt signaling pathway were identified as the significant pathways related to meat quality. This study suggested that the different changes of the myofibrillar protein fraction were involved in the biochemical metabolism in postmortem muscle, which may contribute to the molecular understanding of PSE meat formation.
Highlights
With a reported incidence of 19.17%, pale, soft, and exudative (PSE) meat has always been a major concern in the pork industry [1]
The longissimus thoracis (LT) muscles were divided into the RFN meat group and the PSE meat group according to the pH at 1 h postmortem, and the L* and purge loss at 24 h postmortem
The primary outcome of this study was that PSE meat presented more proteolytic potential and protein changes of the myofibrillar fraction during postmortem aging, with many up-regulated proteins at 1 h postmortem compared to that of RFN meat
Summary
With a reported incidence of 19.17%, pale, soft, and exudative (PSE) meat has always been a major concern in the pork industry [1]. The protein denaturation in PSE meat leads to poor processability and a low yield, resulting in significant losses and a severe hindrance to the pork industry [3,4]. The myocytes enter into a hypoxic-ischemic environment, accelerating glycolysis and energy metabolism, resulting in lactic acid accumulation and pH decline. As the water loss of the myocytes reaches a certain extent, the filaments become thinner, and the reflectance of incident light declines, resulting in paleness [1]. If exposed to high temperatures, the muscle protein denaturation would accelerate [6], leading to further paleness and lower water holding capacity (WHC) [7]
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