Indicators of tenderization are detectable by 12 h postmortem in ovine longissimus1,2

Abstract

Postmortem changes in osmotic pressure; ionic strength; pH; temperature; mu- and m-calpain; calpastatin; desmin degradation; and myofibril fragmentation index (MFI) were determined in ovine longissimus muscle. Our objectives were to characterize changes in these variables and to identify postmortem time points at which significant proteolysis and tenderization (as measured by change in MFI) could be detected. Seven crossbred (Dorset x Romanov) lambs were slaughtered, and samples of the longissimus muscle were removed at 0, 3, 6, 9, 12, 24, 72, and 360 h postmortem. Osmotic pressure increased (P < 0.05) from 379 to 528 mOsm during the postmortem storage period, with two-thirds of the increase occurring within the first 24 h. By measuring conductivity, we showed that ionic strength increased (P < 0.05) from 8.13 to 9.78 mS/cm during the storage period, which is equivalent to 79 and 97 mM NaCl solutions, respectively. In accordance with pH and temperature, conductivity reached ultimate levels at 24 h postmortem. Within 9 h postmortem, mu-calpain activity had decreased (P < 0.05) from at-death values and continued to decrease until 72 h, at which time it was undetectable. It was still possible to detect the 76-kDa isoforms (a product of the autolysis of the 80-kDa subunit of mu-calpain) immunologically, which implies that the loss of activity was not caused by extensive autolysis. In contrast, m-calpain activity remained constant throughout the aging period, whereas calpastatin activity was stable until 24 h postmortem, after which it gradually decreased. Autolysis products of mu-calpain were detected at 3 h postmortem, indicating that mu-calpain was activated some time between 0 and 3 h postmortem. Moreover, the effect of mu-calpain activity on myofibrillar substrates was first observed at 9 h postmortem, when a 23% loss of native desmin was detected. This degradation translated into an increase in MFI at 12 h. Collectively, these results imply that mu-calpain is active in postmortem muscle in the presence of calpastatin, and that effects of mu-calpain activity as determined by increased MFI are detectable during the first 12 h postmortem.

The Electrophoretic Profile Myofibrillar Proteins Extracted From Camel Muscles, Kept in Various Modes

“…This is probably due to a similar proteolysis during this period. Similar results were observed in sheep [23]. However, the small differences in band intensity can be attributed to the difference in the relative amount of protein loaded on the gel electrophoresis as was noted by Martinez et al, [24].…”

“…This suggests an early proteolysis, which can be explained by lower pH thus promoting the activity of proteases. Bands whose molecular weight is in the order of: 13,14,16,18,23,26,33,36, 42 and 53kDa, persisted in the electrophoretic profile of refrigerated muscles or having previously been treated by one organic acid solutions used, between 24 hours and 48 hours postmortem. Intensity was more remarkable at the end of the experiment (48 hours) (Figure 2).…”

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Abstract-Changes in electrophoretic profiles of myofibrillar protein (MFP) in the Longissimus (42, 36, 33,26,23,18,16, 14 and 13 kDa)

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Qualité de la viande de dromadaire dans les abattoirs de Ouargla en Algérie. I. Quelques caractéristiques physico-chimiques de la viande au cours de la maturation

“…Le profil d'augmentation de ce paramètre a été signalé par Troy (24) sur le muscle bovin, et par Veiseth et coll. (25) sur le muscle ovin. …”

The effect of recombinant caspase 3 on myofibrillar proteins in porcine skeletal muscle

“…Approximately half the total desmin detected in the supernatant of the myofibrillar incubations was degraded by 2 and 5 days in myofibrils incubated with high and low levels of rC3, respectively (Table 6). Desmin degradation by calpain has been shown to occur within 1 day in ovine LD (Veiseth et al, 2004) and in bovine semimembranosus (Taylor et al, 1995) at pH 8.3 and 7.0, respectively, with both groups showing significant loss of desmin at the end of the incubation periods. Although desmin degradation was not as rapid in myofibrils incubated with rC3 in comparison to those studies with calpain, the rC3 incubations were performed at a lower pH than those of calpain, which may affect rC3 activity.…”