The objective of this study was to determine whether differences in pork tenderness and water-holding capacity could be explained by factors influencing calpain activity and proteolysis. Halothane-negative (HAL-1843 normal) Duroc pigs (n = 16) were slaughtered, and temperature and pH of the longissimus dorsi (LD), semimembranosus (SM), and psoas major (PM) were measured at 30 and 45 min and 1, 6, 12, and 24 h postmortem. Calpastatin activity; mu-calpain activity; and autolysis and proteolysis of titin, nebulin, desmin, and troponin-T were determined on muscle samples from the LD, SM, and PM at early times postmortem. Myofibrils from each muscle were purified to assess myofibril-bound (mu-calpain. Percentage drip loss was determined, and Warner-Bratzler shear (WBS) force was analyzed. Myosin heavy-chain (MHC) isoforms were examined using SDS-PAGE. The pH of PM was lower (P < 0.01) than the pH of LD and SM at 30 and 45 min and 1 h postmortem. The PM had a higher (P < 0.01) percentage of the MHC type IIa/IIx isoforms than the LD. The-LD had the greatest proportion of (P < 0.01) MHC IIb isoforms of any of the muscles. The PM had the lowest (P < 0.01) percentage of MHC IIb isoforms and a greater (P < 0.05) percentage of type I MHC isoforms than the LD and SM. The PM had less (P < 0.01) drip loss after 96 h of storage than the SM and LD. The PM had more desmin degradation (P < 0.01) than the LD and SM at 45 min and 6 h postmortem. Degradation of titin occurred earlier in the PM than the LD and SM. At 45 min postmortem, the PM consistently had some autolysis of mu-calpain, whereas the LD and SM did not. At 6 h postmortem, some autolysis of mu-calpain (80-kDa subunit) was observed in all three muscles. The rapid pH decline and increased rate of autolysis in the PM paralleled an earlier appearance of myofibril-bound mu-calpain. The SM had higher calpastatin activity (P < 0.05) at 45 min, 6 h, and 24 h and had higher WBS values at 48 h (P < 0.01) and 120 h (P < 0.05) postmortem than the LD. At 48 and 120 h postmortem, more degradation of desmin, titin, and nebulin were observed in the LD than in the SM. These results show that mu-calpain activity, mu-calpain autolysis, and protein degradation are associated with differences in pork tenderness and water-holding capacity observed in different muscles.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1023&context=ans_pubs

Early postmortem biochemical factors influence tenderness and water-holding capacity of three porcine muscles.

PRE-RIGOR PRESSURIZATION OF MUSCLE: EFFECTS ON pH, SHEAR VALUE AND TASTE PANEL ASSESSMENT

The influence of high temperature, type of muscle and electrical stimulation on the course of rigor, ageing and tenderness of beef muscles.

2 – Conversion of Muscle to Meat

Live specimens of the plaice Paralichthys olivaceus were spiked at the brain, stored at various temperatures ranging from 0° to 20°C and examined for changes in rigor tension and ATP degradation in the muscle. The ATP degradation rate was clearly slower at 5–15°C than at WC, resulting in retardation of rigor- mortis onset at the former temperatures. Lactic acid accumulation in the muscle correlated well with the decrease of ATP. The muscle showed an ATP concentration of 3 μmol/g and “rigor index” (full rigor = 100%) at 30% when lactic acid increased up to 30 μmol/g at most storage temperatures. The muscle showed full rigor when ATP completely disappeared and lactic acid attained the maximum plateau (40–50 μmol/g).

Effect of Storage Temperature on Rigor-Mortis and ATP Degradation in Plaice Paralichthys olivaceus Muscle

SUMMARY—
Changes in length and ‘extension’ during the onset of rigor mortis in cyclically loaded strips of ox sternomandibularis muscle were found to be markedly different at 1 °C from those at temperatures over the range 537°C. The delay phase of rigor mortis was longer with lower temperature within the range 1.537°C, but was shorter with lower temperature within the range 1.15°C. The onset phase was longer with lower temperature within the range 5–37°, but was shorter at 1° than at 5°C.

The change in extension was completed sooner at l° than at 5° or 15°C. At 37°C, by the time the change in extension was complete, acid-labile phosphorus had fallen to a low level, and the ultimate pH was closely approached or reached; but at 1°C, an appreciable amount of acid-labile phosphorus still remained, and the pH was considerably above the ultimate value. The shortening at 1 °C was compared to thaw contracture.

R. P. Newbold

Papers

Effect of Temperature on the Time Course of Rigor Mortis in Ox Muscle