|GRAYSON, A.L. - Texas A&M Agrilife|
|King, David - Andy|
|MCKEITH, R.O. - Texas A&M Agrilife|
|MILLER, R.K. - Texas A&M Agrilife|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 6/3/2016
Publication URL: http://handle.nal.usda.gov/10113/62833
Citation: Grayson, A., Shackelford, S.D., King, D.A., McKeith, R., Miller, R., Wheeler, T.L. 2016. The effects of degree of dark cutting on tenderness and sensory attributes of beef. Journal of Animal Science. 94:2583-2591 doi:10.2527/jas2016-0388.
Interpretive Summary: Beef exhibiting the dark-cutting condition due to stress have lean color that is undesirable to the consumer and is heavily discounted, resulting in substantial losses to beef producers. Carcasses that exhibit dark-cutting are known to have differences in tenderness and flavor. However, data addressing varying degrees of dark-cutting is lacking. Thus, this study investigated the impact of four levels of dark colored ribeye lean on tenderness and flavor traits compared to normal red colored controls. This study showed loin steaks with very dark lean color had severe off-flavors. Steaks only slightly dark are most likely to be tough, yet are regularly included in U.S. Select and U.S. Choice product lines.
Technical Abstract: The objective of this study was to determine the effect of degree of dark cutting (DC) on the tenderness, juiciness, and flavor attributes of beef. During carcass grading at a large U.S. commercial beef harvesting facility, DC carcasses (n = 160) and matching normal control (NC) carcasses (n = 160) were selected. Longissimus lumborum (LL) pH was determined and DC carcasses were classified as severe (severe dark cutter [SEDC]; mean pH = 6.9, n = 40), moderate (moderate dark cutter [MODC]; mean pH = 6.6, n = 40), mild (mild dark cutter [MIDC]; mean pH = 6.4, n = 40) or shady (shady dark cutter [SHDC]; mean pH = 6.1, n = 40). Strip loins were obtained from the left carcass sides, vacuum-packaged, and aged at 1°C. Slice shear force (SSF) was measured (14 d postmortem) fresh (never frozen), and trained descriptive sensory analysis of tenderness, juiciness, and flavor was measured (13 d postmortem) on frozen/thawed LL steaks. Cooked SSF pieces were frozen and used for western blotting of desmin to determine extent of postmortem proteolysis. Thaw and cook loss decreased as intensity of DC increased, with SEDC having the lowest loss (1.83% and 10.1%, respectively) compared with NC (3.37% and 14.9%, respectively). Slice shear force was higher (P < 0.05) for SHDC (25.6 kg) and MIDC (22.9 kg) compared to SEDC (16.8 kg), MODC (19.4 kg) and NC (17.8 kg). Sarcomere length was shorter (P < 0.05) between DC class (1.66, 1.67, 1.71, and 1.73 µm for SEDC, MODC, MIDC and SHDC, respectively) and NC (1.86 µm). Postmortem proteolysis of desmin was greater (P < 0.05) for NC compared with all DC classes (59.83% vs. 49.20%, 40.31%, 42.07% and 43.30% for SEDC, MODC, MIDC and SHDC, respectively). Trained sensory panel ratings for tenderness differed (P < 0.05) among DC class with SEDC (6.51) the most tender followed by MODC (6.04) and then MIDC (5.19), whereas SHDC (4.66) and NC (4.93) were the toughest. Juiciness ratings differed (P < 0.05) among each DC class (5.9, 5.7, 5.4, and 5.2 for SEDC, MODC, MIDC and SHDC, respectively), with no difference between MIDC or SHDC compared with NC (5.23). Fat-like, rancid, heated oil, chemical, and musty/earthy/hummus flavors increased (P < 0.05) whereas metallic, sour, and salty flavors decreased as severity of DC increased. This study showed DC and NC differed in LL tenderness, juiciness, and flavor. The direction and/or magnitude of those differences were greatly dependent on severity of DC. Steaks with intermediate pH (SHDC and MIDC) are most likely to be tough and are regularly included in U.S. Select and U.S. Choice product lines.