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Title: Tenderness of pasture versus grain fed beef aged 14 and 28 days

item PFEIFFER, KASSANDRA - Oklahoma State University
item MAFI, GRETCHEN - Oklahoma State University
item VANOVERBEKE, DEBORAH - Oklahoma State University
item RAMANATHAN, RANJITH - Oklahoma State University
item Neel, James

Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2015
Publication Date: 8/3/2015
Citation: Pfeiffer, K.E., Mafi, G.G., Vanoverbeke, D.L., Ramanathan, R., Neel, J.P. 2015. Tenderness of pasture versus grain fed beef aged 14 and 28 days. American Meat Science Association Conference Reciprocal Proceedings. Available:

Interpretive Summary:

Technical Abstract: Consumer interest in pasture versus grain fed beef has been on the rise in recent years. This interest could be sparked by the public’s concerns of beef management techniques and processing impacts on the nutrition and safety of their food, as well as the environmental impact of each management type. Peaked interest in pasture versus grain fed beef has also brought into question if palatability differences exist between the two types of beef. The objective of this study was to evaluate the difference in tenderness between pasture and grain fed beef, and the effects different aging times would have. All cattle were on forage diets during the entire stocking period. For finishing, cattle were randomly assigned to either a conventional grain based diet or pasture finished on alfalfa. Conventionally finished cattle were fed for 94 d, and alfalfa cattle were on pasture for either 88 or 130 d. Average age of animals at slaughter was 18.2 mon for concentrate fed and 18.9 mon for alfalfa finished. Strip loins (n = 107) were cut 2.54 cm thick and vacuumed packaged. From the loin end, the second steak was used for Warner-Bratzler (WBS) 14 d, the fourth steak was used for Slice Shear (SS) 14 d, the seventh steak was used for SS 28 d, and the eighth steak was used for WBS 28 d. The steaks were aged 14 or 28 d at 4ºC. At the end of each aging time, steaks were frozen at -20ºC. Steaks were thawed at 4ºC 24 h prior to cooking. The steaks used for WBS and SS were cooked in an impingement oven at 200ºC to an internal temperature of 68ºC. Temperatures were measured as the steaks exited the oven, if they had not yet reached 68ºC they were returned to the conveyor until they reached 68ºC. WBS steaks were cooled overnight at 4ºC. WBS steaks were allowed to reach room temperature prior to coring. The cores were done by hand and 1.27 cm in diameter cores were taken from the middle of the steak parallel to longitudinal orientation of muscle fibers so shearing action was perpendicular to the longitudinal orientation of muscle fibers. There were six cores collected per sample. For SS, the final temperature of steaks was recorded. The lateral of each steak was removed, a 1 cm thick, 5 cm long slice was cut parallel to the muscle fibers. A Warner-Bratzler Meat Shear fixture was used for WBS and a Flat Shear Blade was used for SS, these blades were attached to an Instron Universal Testing Machine (Model 5943, Instron Corporation, Norwood, MA). The crosshead speed was 200 mm/min and software utilized was Bluehill 3. The data were analyzed using the Mixed Procedure of SAS. The aging by feeding regime interaction was tested, and no interaction was observed. For WBS, 14 d steaks were more tender (P<0.05) than 28 d aged steaks. However, WBS values for both treatments were well below the typically considered steak tenderness threshold of 3.5 kg, 2.04 kg for 14 d and 2.65 kg for 28 d. No differences (P>0.05) were found between the two finishing types. For SS, there was no significant difference between aging times (P>0.05). The results indicate there is no difference in tenderness of grass fed versus grain fed steaks. Additional research will be conducted to evaluate subjective tenderness, as well as flavor and juiciness.