Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2007
Publication Date: 6/11/2007
Citation: Zapata, I., Leeds, T.D., Mousel, M.R., Wick, M.P. 2007. Sarcomere length dynamics of postmortem ovine Psoas major and Longissimus dorsi muscles.. Journal of Animal Science Supplement. 86(1):282. Interpretive Summary: Tenderness influences a consumer’s perception of the quality of a cooked meat product. To enhance consumer acceptance, domestic meat-animal industries are committed to producing products that are consistently tender. Achieving this degree of consistency requires knowledge of the biological and environmental factors that ultimately determine product tenderness. The research reported here investigates the difference of sarcomere lengths between two lamb muscles (the loin and the tenderloin) at two time points after harvest. In muscle, the sarcomere is the basic unit of contraction. During the conversion of muscle into meat (aging), the length of the sarcomere changes. Results of this research suggest that the sarcomere lengths are different between the loin and the tenderloin in lamb. Also, the change in sarcomere length during aging is different between the muscles. However, based on data from this study, there was no conclusive evidence of a relationship between sarcomere length and tenderness.
Technical Abstract: Understanding relationships between biological mechanisms of postmortem events in muscle and meat quality is of enormous importance for the meat industry. Because sarcomere length has been previously related to tenderness issues in lambs, we decided to study two contrasting types of muscle with known differences in tenderness characteristics. The objective of this study was to compare the sarcomere length (SL) dynamics of postmortem ovine Psoas major (PM) and Longissimus dorsi (LD) muscles at two time points and to relate LD tenderness to SL. Samples from the PM and LD muscles were removed from 57 animals at 50 min and at 36 h postmortem at the abattoir in the Ohio State University meat science laboratory. Muscle tissue free of evident fat or connective tissue was dissected from each sample and fixed in a glutaraldehyde/cacodylic acid buffer (pH 7.1). Samples were homogenized in cacodylic acid buffer (pH 7.1), mounted on glass slides, and observed by phase contrast microscopy. Images were captured with a CCD camera and evaluated for SL using image analysis software. The LD chops were assayed at 7 d postmortem for tenderness using Warner-Bratzler shear (WBS) force. Repeated SL data were described using a mixed effects model in SAS with fixed time, muscle, and interaction effects and a random animal effect. The relationship between SL and WBS was evaluated using a Pearson’s correlation test. The SL were significantly different from each other within each muscle group and over time (P < 0.001). Least squares means estimates of SL for the PM were 2.275 ± 0.023 'm at 50 min and 2.888 ± 0.032 'm at 36 h. Least squares means estimates of SL for LD were 1.835 ± 0.023 'm at 50 min and 1.736 ± 0.016 'm at 36 h. Estimate differences were 0.613 ± 0.040 'm (P < 0.001) for PM and -0.098 ± 0.028 'm (P < 0.001) for LD. A Pearson's correlation test showed no relation between LD SL and WBS force at either time point. These results demonstrate inherent differences in the postmortem SL dynamics between the two muscles. That is, the PM exhibited a positive slope in SL during postmortem aging while the LD SL exhibited a negative slope over the same time frame. Currently, the biological mechanism underlying this phenomenon has yet to be elucidated and is actively being pursued in our laboratory.