LAUSR

Meat discoloration starts from the interior and rises to the surface of steaks. Recently developed near-infrared single-fiber probe (SFP) in our laboratory allows characterizing interior color changes. The objective was to determine how changes in surface and interior metmyoglobin correlate with color changes in psoas major muscle during retail display. Seven USDA Select tenderloins were collected from a commercial processing facility. Steaks were cut from each muscle and placed in polyvinyl chloride overwrap trays for retail display. The SFP was a 400-µm fiber in a 5-gauge needle and inserted into the muscle at five positions with each position increasing in depth by mm. A mathematical model developed in MATLAB determined the percent metmyoglobin at each depth and day. Surface color was analyzed using a HunterLab MiniScan spectrophotometer each day and percent metmyoglobin was determined. Steaks were randomly assigned to analysis of oxygen consumption (OC) and metmyoglobin reducing activity (MRA) of the interior and retail surfaces on d 0, d 3, and d 5 of display. Pearson’s correlation coefficients were used to evaluate the relationship between calculated percentages, color stability parameters, and retail color with significance considered at a P < 0.05. Metmyoglobin determined by the SFP increased at all depths during display with greater metmyoglobin at shallower depths. Metmyoglobin calculated by the SFP at mm and by HunterLab spectrophotometer were strongly negatively (P < 0.05) correlated with a* values during retail display. The MRA determined using the retail surface was strongly negatively (P < 0.05) correlated with HunterLab surface metmyoglobin and SFP metmyoglobin at mm depth. The OC of the retail surface was moderately negatively correlated (P < 0.05) with HunterLab surface metmyoglobin and SFP metmyoglobin at all depths. The development of internal metmyoglobin demonstrated a strong relationship with retail color and negatively impacted color stability attributes.