Muscle of dark and normal beef differs metabolically

Authors: KIRKPATRICK, L - Virginia Polytechnic Institution & State University; GOMEZ, J.F.M. - Virginia Polytechnic Institution & State University; BELINE, M - Virginia Polytechnic Institution & State University; YEN, C - Virginia Polytechnic Institution & State University; BODMER, J - Virginia Polytechnic Institution & State University; WICKS, J - Virginia Polytechnic Institution & State University; SHI, H - Virginia Polytechnic Institution & State University; SILVA, S - Universidade De Sao Paulo; AALHUS, J - Agriculture And Agri-Food Canada; King, David - Andy; GERRARD, D - Virginia Polytechnic Institution & State University

Submitted to: Meat Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2023
Publication Date: 12/1/2023
Citation: Kirkpatrick, L.T., Gomez, J.F.M., Beline, M., Yen, C.N., Bodmer, J.S., Wicks, J.C., Shi, T.H., Silva, S.L., Aalhus, J.L., King, D.A., Gerrard, D.E. 2023. Muscle of dark and normal beef differs metabolically. Meat Science. 206. Article 109344. https://doi.org/10.1016/j.meatsci.2023.109344.
DOI: https://doi.org/10.1016/j.meatsci.2023.109344

Interpretive Summary: Beef lean color is highly dependent on the rate and extent of pH decline in the muscle after harvest. Carcasses with muscles that display the dark cutting condition generally have not undergone the normal pH decline. However, some carcasses display dark lean despite having undergone sufficient pH decline and are termed atypical dark cutters. This study demonstrated that atypical dark muscles have more oxidative muscle metabolism, but similar capacity for glycolytic metabolism compared to muscles with normal lean color. Thus, these results suggest that more oxidative muscles may be more prone to producing dark colored beef.

Technical Abstract: Reduction in muscle glycogen triggered by adverse antemortem handling events alters postmortem energy metabolism and results in a high ultimate pH and dark, firm and dry beef, often referred to as ‘dark-cutting’. However, the relationship between atypical dark (AT) beef, postmortem energy metabolism and underlying tissue characteristics remains somewhat unclear. Cattle harvested in the US and Canada representing normal (pH < 5.6), AT dark (pH 5.6 - 5.8) and dark cutting (DC; pH > 5.8) beef were analyzed for tissue characteristics related to energy metabolism. Results show AT dark beef is more oxidative but similar to normal beef in glycolytic potential and nucleotide abundance. Mitochondria DNA content (P < 0.05; Canada, P < 0.005; US) and oxidative enzymes for DC and AT dark beef were greater (P < 0.01; Canada and US) compared to normal beef. Myoglobin tracked (P < 0.01) with color classification. These findings show both DC and AT beef are inherently more oxidative and raise the possibility that more oxidative muscle may be more prone to develop dark beef.