Effect of packaging and frozen storage temperature on beef pigments.

Met-, oxy-and myoglobin relative surface concentrations were determined using reflectance spectrophotometry. Pigment behaviour during storage of beef packaged in films and oxygenation of vacuum-packaged samples were described by different reaction schemes and modelled to obtain kinetic and equilibrium constants. Comparative studies performed with beef samples refrigerated, frozen to -5 deg C and stored at this temperature (partial freezing), and frozen to -25 deg C and stored at -5 and -20 deg C, indicated that for aerobic storage periods of 90 days, metmyoglobin levels of partially frozen samples upon thawing were comparable to those of frozen samples stored at -20 deg C. For vacuum-packaged beef, pigment concentrations remained practically constant during frozen storage; partial freezing increased oxygenation capacity of the tissue compared with chilled and frozen conditions.