Sensory and processing properties of cured semimembranosus muscle from stress-susceptible pigs treated with porcine somatotropin.

Forty-eight Yorkshire cross pigs of three stress susceptibility classes (stress positive, stress-carrier, and stress negative) were injected daily with porcine somatotropin (pST; 4 mg/d) or placebo. Each pig was injected in the neck once daily until taken off test, starting when the pigs weighed 59 kg. Porcine somatotropin treatment was terminated at weekly intervals as individual pigs reached 109 kg, but animals continued to be fed for six additional days to allow for required withdrawal time. The effect of pST and stress classification on the sensory, physical, chemical, and processing characteristics of cured semimembranosus (SM) muscle was evaluated. Treatment of animals with pST had no effect on the sensory scores, lipid and protein content, cooking yields, or color values of SM muscle slices. Semimembranosus muscles from stress-positive animals, however, had reduced sensory scores for texture, flavor, and overall palatability. Semimembranosus muscles from stress-positive pigs also had smaller cooking yields and greater Hunter a and b values of processed slices. The greater Hunter a and b values suggested that the color of these slices were redder and yellower than the color of SM muscle slices from negative and carrier animals. Semimembranosus muscles from stress-susceptible animals also had a significantly lower lipid content. Treatment of animals with pST did not significantly alter sensory, chemical, or processing characteristics of SM muscle slices from these animals.