Meat color as perceived by consumers serves as a valuable guide for assessing overallquality and wholesomeness of meat. The bright cherry-red color of beef is influenced by tissue oxygen consumption, obstacles to oxygen diffusion, and thickness of the oxymyoglobin layer. The dynamics of meat color depend on several physical properties of muscle including myoglobin redox status and concentration. Physical, chemical, and anatomical differences in muscles cause large variations in color from cut to cut, within a cut, and in cuts made parallel or perpendicular to muscle fibers. Clearly, muscle fiber orientationaffects measurements of tenderness and cooking yields; however, variations in myoglobin redox dynamics, oxygen penetration, and color stability due to muscle fiber orientation (parallel or perpendicular) are not well documented. Among the various meat color measurement techniques available, near-infrared (NIR) methods have the advantages of being nondestructive, rapid, inexpensive, and adaptable for online measurements. The NIR tissue oximeter is a relatively new biomedical device that has been used inexercise physiology and in medicine to measure hemoglobin and myoglobin oxygensaturation in brain tissue and cardiac and skeletal muscle. This instrument seems tohave promise for use in measuring inherent properties of meat that are related to meatcolor stability. NIR tissue oximetry may provide continuous real-time measurements ofchanges in myoglobin oxygen status, thus providing information on tissue oxygenationand hemodynamics. The unique feature of the tissue oximeter is that it uses the theory ofphoton migration through tissue, allowing for absolute measurement of absorption in,for example, human or animal tissue. If the NIR absorption properties of any chromophoreare known, quantitative analysis of color compounds is possible without constantcalibration and validation. We are not aware of any research in which NIR tissue oximetryhas been used to evaluate color of post-rigor meat. This study was designed to evaluate whether NIR tissue oximetry has promise for measuring meat properties related to meat color. Specific objectives were to determine: (1) effects of parallel vs. perpendicular muscle fiber orientation of meat cuts on NIR measurements, (2) amounts of deoxymyoglobin (DMb), oxymyoglobin (OMb), and total myoglobin (TMb) in the superficial and subsurface layers of beef muscle (longissimus)stored in several packaging formats, and (3) tissue oximeter responses to post-rigormuscle fiber orientation and surface measures of color.
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