The relationships between glycogen stores and muscle ultimate pH in commercially slaughtered pigs

Small samples of liver and m. adductor (AD) were collected within 45 minutes of death from the carcasses of a total of 604 pigs killed at three bacon factories. Glycogen concentrations were measured and part of the muscle sample allowed to complete post-mortem glycolysis in order to estimate ultimate pH (pHu) values. Liver glycogen levels were also used to predict overall food withdrawal times. Muscle glycogen concentrations ranged from 2.2 to 15.3 mg/g, liver glycogen from 0.01 to 50.7 mg/g and pHu in the AD from 5.51 t 6.76. The overall average predicted fasting time was 16.5 +/- 0.54 (SEM) hours and 22% of pigs had pHu values in the AD greater than 6.2 indicative of potentially dark, firm, dry meat. Muscle glycogen concentration was positively correlated with liver glycogen (r = 0.27, P less than 0.01) and negatively correlated with predicted fasting time (r = -0.30, P less than 0.001). The pHu in the AD was negatively correlated with liver glycogen (r = -0.34, P less than 0.001) and positively correlated with predicted fasting time (r = 0.37, P less than 0.001). Therefore, pigs which had reduced concentrations of glycogen in their livers, indicative of longer food withdrawal times before slaughter, tended to have less glycogen in their muscles and a higher pHu in the meat.