55-2 |
Influences of chemical characteristics of beef inside and outside semimembranosus on color traits |
L. M. SAMMEL1, M. C. Hunt, and D. H. Kropf. (1) Dept. of Animal Sciences & Industry, Kansas State Univ., 224 Weber Hall, Manhattan, KS 66506-0201 Faster discoloration of the deep or inside semimembranosus (ISM) than the superficial or outside semimembranosus (OSM) reduces shelf life and functionality of the muscle in modified atmosphere packaging. Differences in postmortem temperatures and pHs in the ISM and OSM may alter oxidation and reduction of myoglobin. However, most research involving the semimembranosus does not differentiate between the two muscle portions. Information on chemistry of the ISM and OSM could be used to optimize postmortem conditions thereby increasing color life and improving salability. We examined influences of pre-rigor temperature and pH decline on chemistry of the ISM and OSM in relation to initial color and stability. Combinations of electrical stimulation, no stimulation, cold-boning, and hot-boning were used to create different postmortem declines in temperature and pH for the ISM and OSM. Chemical characteristics as well as visual and instrumental color traits were measured. Cold-boned ISM had a slower chill rate; faster pH decline; more denatured protein; less metmyoglobin reducing ability, oxygen consumption, and water holding capacity; and a lighter, less stable color than the OSM. Cold-boned steaks were two-toned in color and discolored by day 3 of display. Hot-boned ISM and OSM chilled at the same rate and had similar pH declines, similar chemical characteristics, and acceptable color traits up to day 5 of display. Myoglobin concentration, heme iron, nonheme iron, or lipid oxidation did not explain differences in color stability between the ISM and OSM. These results define color influencing chemical characteristics damaged by high temperature/low pH conditions typical of muscles positioned deep within the round. Techniques that chill the beef semimembranosus faster will produce uniform stable color by conserving reducing ability and protein integrity. Extending the color life of the ISM should prevent the need for reworking and discounting of the semimembranosus after only 2 days of retail display.
Session 55, Muscle Foods: Fresh Meat Quality
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