Muscle fiber and color characteristics of different locations within beef Longissimus lumborum steaks

Monday, July 21, 2014: 11:45 AM
3501D (Kansas City Convention Center)
Kelsey J Phelps , Kansas State University, Manhattan, KS
Mathew A Vaughn , Kansas State University, Manhattan, KS
Sara M Ebarb , Kansas State University, Manhattan, KS
Derris D Burnett , Kansas State University, Manhattan, KS
James S. Drouillard , Kansas State University, Manhattan, KS
John M. Gonzalez , Kansas State University, Manhattan, KS
Abstract Text:

The objective of this study was to demonstrate the effect that muscle fiber composition differences within anatomical location of beef strip loin steaks elicit on color characteristics over a 7-d simulated retail display. Beef strip loins (n=120) were collected from a commercial abattoir and before aging, steaks were removed from the 13th rib for immunohistochemical analysis of muscle fiber cross-sectional area (CSA) and myosin-heavy chain (MHC) isoform distribution. Sampling locations included medial (MED), mid-lateral (M/L), and lateral (LAT) within each steak. After 14-d of aging, steaks were fabricated and L*, a*, surface metmyoglobin, and metmyoglobin reducing ability (MRA) were analyzed during a 7-d simulated retail display.  There was a day×location interaction for all color characteristics (P<0.01).  Initially, LAT was darker and redder than both MED and M/L (P<0.04), and M/L was redder (P<0.01) than MED. On d-7, MED tended to have reduced (P<0.05) L* value than the M/L and LAT area.  The MED area was more (P<0.05) red than LAT, while M/L did not differ in redness compared to the other areas (P>0.10). On d-0, all three treatments differed in surface metmyoglobin percentage with the MED possessing greater a percentage than the other locations (P<0.01).  At the end of display, all three treatments differed with the LAT possessing 0.83% and1.75% more metmyoglobin than M/L and MED, respectively (P=0.01).  All locations had similar MRA on d 0 (P>0.10), but treatments differed in MRA on d-7 (P<0.05). The MED possessed 3.01% and 6.19% greater MRA than LAT and M/L, respectively (P<0.05). Percentage of type IIA fibers was not different between the three locations (P>0.10).  The MED area tended to possess fewer type I fibers (P=0.10) than the M/L, and MED possessed less (P<0.01) type I fibers than LAT. Type I fiber number in LAT and M/L did not differ (P=0.25).  The MED area had more (P=0.02) type IIX fibers than the M/L and LAT (P<0.02), but the M/L and LAT did not differ (P=0.94). The M/L area had larger type I and IIX fibers than MED and LAT (P<0.01), and MED tended to have larger (P=0.08) type I fibers than LAT. Also, LAT had smaller (P<0.01) IIA fibers than M/L and MED, but size of IIA fibers in M/L and MED were similar (P>0.10). Based on fiber distribution, expected biochemistry of these locations does not accurately explain color characteristics during simulated retail display.


Fiber type, color characteristics, sampling location