Development of a model system to mimic beef bone discoloration

Some current practices used in the meat industry (blast chilling, enhancement, modified atmosphere packaging [MAP]) appear to result in darkening of the bone in fresh meat. The objective of this study was to develop a model system that could be used to evaluate intervention strategies to prevent this discoloration. Beef rib bones were removed from carcasses, split along the transverse plane from the proximal to the distal end of the rib, and then frozen (-20 degrees C) or held at 4 degrees C for 24 h. Half were exposed to a phosphate/salt enhancement solution while half served as the control. Samples were packaged in air or modified atmosphere packaged (MAP: 80% O2/20% CO2) and displayed in a retail case (4 degrees C, 24 h). Visual discoloration occurred during the 1st 10 h of display. More darkening (brown, green/black) was observed in previously frozen samples, whereas samples held at refrigeration temperature were redder. CIE L*, a*, and b* values determined after 24 h indicated that samples held in refrigeration before packaging were lighter and redder. After 24 h at 4 degrees C, previously frozen samples contained more methemoglobin/g protein in the bone marrow than did bone samples that had never been frozen.