|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1994 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1993 : ¥1,600,000 (Direct Cost : ¥1,600,000)
The purpose of this study was to elucidata the cause of very rare development of PSE musculature in the porcine carcass slaughtered after CO_2-anaesthetization (stunning).
We slaughtered swines by bleeding after CO_2-anaesthetization using Combi plant 44 (Butina ApS.Denmark) with 80%CO_2,70sec inhalation.In this equipment, swines were chased into gondolas through a run way using electric pick (100V). Consequently, stress loading to swines were so heavy that adrenaline level released in blood was two times or more, compared with electrially stunned ones, nevertheless, PSE musculature was scarcely found in them. Then, investigations to resolve this conflict were conducted as follows :
The pH change curve of muscles from manual electric stunning (180V,10 sec) monotonously declined from physiological pH (7.45) to acidic ultimate pH during postmortem time course to 24 hrs. On the contrary, those from CO_2-stunning showed very low pH (pH_<0.5> 6.2) at the initial stage postmortem. However, it
rose during about 3 hrs. (pH_3 6.7), after that, it declined to ultimate pH slowly. It was confirmed that the low pH at initial stage postmortem was caused by respiratory acidosis, based on the high level of carbonate content in muscle, from the results of HPLC determination. And pH-rising during 3 hrs.after slaughter was presumed to be caused by decomposition of carbonate by the reaction of carbonic anhydrase. Adenyl cyclase activity, pH-dependent, in muscle cell was restrained to form cAMP,on account of low pH below 7.2 at the initial stage postmortem. Accordingly, lactic acid production was also retarded. However, as pH rose about 3 hrs.later, cAMP formation was recovered, so the postmortem glycogenolysis (metabolic acidosis) was also promoted to produce lactic acid, to attain ultimate pH after 24 hrs.
In general, it is recognized that PSE musculature in pork develops in the case that the rapid pH drop within short period after slaughter, before the natural body heat have been dissipated through carcass chilling, causes denaturation of muscular contractile and regulatory proteins. In contrast with it, it was evident that, low pH of muscles from CO_2-stunned swines at the initial stage postmortem, though carcass temperature should be high, the progress of metabolic acidosis was depressed. Less