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

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Dodge, Jamie
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Animal Science

The Department of Animal Science originally concerned itself with teaching the selection, breeding, feeding and care of livestock. Today it continues this study of the symbiotic relationship between animals and humans, with practical focuses on agribusiness, science, and animal management.

The Department of Animal Husbandry was established in 1898. The name of the department was changed to the Department of Animal Science in 1962. The Department of Poultry Science was merged into the department in 1971.

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The objective of this experiment was to examine the relationship between rate of tenderization and drip loss with [Mu]-calpain activity, [Mu]-calpain autolysis, [Mu]-calpain localization (in sarcoplasmic portion vs. myofibrillar portion), calpastatin activity, and postmortem proteolysis in three different muscles that differed in water-holding capacity or tenderness. Halothane negative Duroc pigs (n=16) were harvested. Temperature and pH measurements were taken in the longissimus dorsi (LD), semimembranosus (SM), and psoas major (PM). Samples were collected from the LD, SM, and PM to determine calpastatin activity, assess [Mu]-calpain activity and autolysis, and examine proteolysis of titin, nebulin, desmin, and troponin-T. Myofibrils were purified (assess myofibril-bound [Mu]-calpain), percent drip loss was determined, Warner-Bratzler shear force was analyzed, and myosin heavy chain (MHC) isoforms were examined. The PM had a greater percentage of MHC type IIa isoforms than the LD and a greater percentage of type I MHC isoforms than the LD and SM. The LD, SM, and PM were significantly different for percentage of MHC IIb + IIx isoforms with the LD>SM>PM. The PM had significantly lower pH (at 30 min, 45 min, and 1 h postmortem), significantly less drip loss (after 96 h of storage), significantly more desmin degradation product (at 45 min and 6 h postmortem), and a faster rate of titin degradation than the LD and SM. The PM also had partial autolysis of the [Mu]-calpain 80-kDa subunit at 45 min postmortem whereas all three muscles had partial autolysis of the [Mu]-calpain 80-kDa subunit at 6 h postmortem. The rapid pH decline and increased rate of autolysis in the PM paralleled an earlier appearance of myofibril-bound [Mu]-calpain. The SM had significantly higher WBS (at 48 h and 120 h postmortem) and higher calpastatin activity (at 45 min, 6 h and 24 h postmortem) than the LD. The LD had greater loss of intact desmin at 48 h and 120 h than the SM at 48 h and 120 h postmortem. These results show that the relationships between [Mu]-calpain activity, [Mu]-calpain autolysis and location, calpastatin activity, and protein degradation can explain some variation in tenderness and drip loss of fresh pork products.

Tue Jan 01 00:00:00 UTC 2002