Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 12/7/2015
Publication Date: 3/14/2016
Citation: King, D.A., Shackelford, S.D., Wheeler, T.L. 2016. Intramuscular variation in fresh ham muscle color. [abstract] Journal of Animal Science Supplement. 94(Supplement2)61. doi:10.2527/msasas2016-131.
Technical Abstract: This experiment was conducted to characterize a defect involving pale muscle tissue in the superficial, ventral portion of ham muscles, resulting in two-toned appearance of cured ham products. Biceps femoris muscles (n = 200), representing 3 production systems, were obtained from the ham-boning line of a large commercial processor. Instrumental color attributes were determined on the medial and lateral surfaces of the muscle before they were sliced (2.54-cm-thick) perpendicular to the long axis of the muscle. Slices were numbered from the proximal end of the muscle. Severity of the defect was greatest on the distal end of the muscle corresponding to slices 6, and 7. The superficial (affected) portion of these slices was separated from the deep (unaffected) portion. Myoglobin concentration and muscle pH were determined on both portions. The medial surface of the muscle had much lower (P < 0.05) L* (53.1 versus 63.4) and higher (P < 0.05) a*(23.2 versus 15.3) and b* (18.5 versus 15.4) values than the lateral surface. Compared to the superficial portion, the deep portion of the muscle had higher (P < 0.05) muscle pH (5.68 versus 5.51) and myoglobin content (1.98 versus 0.86 mg/g). Muscle pH and myoglobin content explained 20 and 7% of the variation in L* values of the deep portion of the muscle, respectively. Conversely, myoglobin content and muscle pH explained 28 and 8% of the variation in L* values in the superficial portion of the muscle, respectively. Similar relationships were seen with regard to a* values. Five minimally affected and 5 severely affected muscles were sampled in the superficial and deep portions for muscle fiber type determination. Fiber type distribution did not differ (P > 0.05) between the deep and superficial portions of the minimally affected muscles. However, in severely affected muscles, the deep portion had an increased (P < 0.05) proportion of red fibers, and concomitant decrease (P < 0.05) in white fibers relative to the superficial portion of the muscle. Muscle fiber areas were smaller (P < 0.05) in the severely affected muscles, regardless of location. These data indicate that the superficial portion of the muscle is much lighter and less red in color which is caused by a lack of myoglobin content in this portion of the muscle and is associated with a shift in muscle fiber type.