Journal of Animal Science, Vol 69, Issue 7 2865-2870, Copyright © 1991 by American Society of Animal Science

JOURNAL ARTICLE

Effect of porcine somatotropin, stress susceptibility, and final end point of cooking on the sensory, physical, and chemical properties of pork loin chops

J. A. Boles, F. C. Parrish Jr, C. L. Skaggs and L. L. Christian
Dept. of Anim. Sci., Iowa State University, Ames 50011.

Forty-eight pigs of three known stress susceptibility classes were injected daily with porcine somatotropin (pST; 4 mg/d) or a placebo. Each pig was injected in the neck once daily until taken off test, starting when the pigs weighed 59 kg. The pST treatment was terminated at weekly intervals when 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, and chemical characteristics of pork chops was observed. Also, the effect of two end-point temperatures (71 and 77 degrees C) on the sensory attributes was observed. The pST treatment of animals resulted in a small but significant decrease in panel scores for tenderness, juiciness, and flavor. Stress susceptibility class, however, decreased panel scores for tenderness only. The pST treatment reduced intramuscular fat and increased moisture in the longissimus muscle, but stress susceptibility class had no effect on proximate composition. The pST treatment and stress susceptibility decreased and increased Hunter L values of chops, respectively, indicating darker and lighter colors, respectively. Furthermore, a greater end-point temperature reduced sensory scores for tenderness and juiciness. These results suggest that pST treatment does not cause an increased incidence of pale, soft, exudative muscle. Also, the use of a lower temperature of end-point doneness (71 degrees C) should be implemented to optimize palatability of broiled pork chops regardless of pST treatment.