| Oxymyoglobin layer depth (OLD), metmyoglobin layer depth (MLD) and color attributes of beef Longissimus lumborum (LL; color-stable) and Psoas major (PM; color-labile) muscles from various postmortem times (PT; 3, 5, 10, or 14 d in vacuum at 0 or 4.4°C) were investigated during 120-h display (0 or 3.3°C). Dynamics of myoglobin layer changes during simulated retail display were studied on muscle cubes in open-topped, clear PlexiglasRTM cubes polyvinylchloride film over top using digital image photography and analysis. LL and PM steaks were visually scored and cubes and steaks instrumentally evaluated for surface reflectance color attributes.; LL compared to PM had deeper OLD at 3, 24, 72, and 120 h display, also thinner MLD and brighter red steaks at 24 and 72 h.; After 120 h, muscle and PT interacted for redness, surface OMb and MMb, and OLD. PT 14 d had the least surface OMb, most surface MMb, thinnest OLD, and was less red.; Longer PT (10 or 14 d) provided better 3 h color bloom, but color stability decreased. LL reached borderline panelist acceptability score at 91 h (23% MMb, 4.22 mm-OLD, 2.50 mm-MLD); PM in 31 h (23% MMb, 1.88 mm-OLD, 1.88 mm-MLD). At 3, 24, and 72 h display, OLD thickness minus MLD thickness was 3.44, 3.83, and 2.55 mm for LL and 2.00, -0.05, and -1.57 mm for PM. At 120 h for LL, this decreased (2.42, 1.85, -0.12, and -2.12 mm for increasing PT), while PM muscle values ranged from -2.57 to -3.36 for PT. Greater O2 penetration during bloom, thicker OLD, and slower developing MLD during display contributed to color stability. Oxygen consumption and reducing capacity of muscles were likely related to myoglobin layer change, surface color bloom and display stability of both muscles. |
