Effects of aging on the fundamental color chemistry of dark-cutting beef.

The objective of the current study was to evaluate the effects of aging on myoglobin chemistry of dark-cutting beef. Ten USDA Choice (mean pH = 5.6; normal pH beef) and 10 no-roll dark cutter (mean pH = 6.4) strip loins were obtained from a commercial packing plant within 3 d of harvest. Loins were cut into 4 sections, vacuum packaged, randomly assigned to 0-, 21-, 42-, and 62-d aging at 2°C in the dark. Following aging, loin sections were cut into 2.5-cm-thick steaks and were used to determine bloom development, oxygen consumption (OC), metmyoglobin reducing activity (MRA), and lipid oxidation. Surface color readings were measured using a HunterLab Miniscan XE Plus spectrophotometer. A significant muscle type × aging time interaction resulted for OC ( < 0.001). Normal pH steaks declined more ( < 0.001) in OC during aging than dark-cutting beef. On d 0, dark-cutting beef had a greater OC ( < 0.001) than normal pH beef. There was a significant muscle type × oxygenation time × aging period interaction for L* values, deoxymyoglobin (DeoxyMb), and oxymyoglobin (OxyMb). When dark-cutting sections were aged for 62 d, both 0 and 60 min bloom development L* values were greater ( < 0.0001) than 0 min dark-cutting sections aged for 21 or 42 d. At all aging periods, normal pH beef had greater OxyMb content and lower DeoxyMb ( < 0.0001) during bloom development than dark-cutting beef. An aging period × muscle type interaction was significant for % overall reflectance ( = 0.0017) and absorbance ( = 0.0038). Dark cutting and normal pH beef loin sections aged for 62 d had greater reflectance ( < 0.0001) than 21 d. On d 0, dark-cutting beef had greater ( < 0.0001) MRA than normal pH beef. There were no significant ( = 0.14) differences in MRA between 42 and 62 d between dark-cutting and normal pH beef. Dark cutting steaks had lower thiobarbituric acid reactive substances values ( < 0.0001) than normal pH steaks. The results indicate that characterizing the myoglobin chemistry during aging will help to design strategies to improve appearance of high pH beef.