Effects of fibre orientation, myoglobin redox form, and postmortem storage on NIR tissue oximeter measurements of beef longissimus muscle.

To determine near-infrared tissue oximeter responses to muscle fibre orientation, display time, and surface colour differences of beef longissimus lumborum steaks, beef loins were cut into steaks either perpendicular or parallel to the muscle fibre orientation. Surface colour differences were created by packaging steaks in vacuum (VAC), 80% O(2) and 20% CO(2) modified atmosphere packaging (HiOx MAP), polyvinyl chloride film overwrap (PVC), and HiOx MAP converted to PVC (HiOx-PVC) after 2days. Changes in surface colour and subsurface pigments during display (0, 2, 4, 10, and 15days at 2 degrees C) were characterized by using a reflectance-spectrophotometer and a near-infrared tissue oximeter, respectively. Fibre orientation, storage, and packaging affected (P<0.05) colour, total pigment, deoxymyoglobin, and oxymyoglobin content. Tissue oximetry measurements appear to have potential for real-time monitoring of myoglobin redox forms and oxygen status of packaged meat, but fibre orientation needs to be controlled.