EFFECTS OF COLD STORAGE ENVIRONMENT ON COLOR OF EXPOSED LEAN BEEF SURFACES

Abstract

ABSTRACTA model system approach utilizing a wind tunnel designed to control temperature, humidity and air velocity was used to evaluate the effects of cold storage conditions on the color of exposed lean beef surfaces. Measurements made on the stored samples included: evaluation of pigment oxidation rate by reflectance spectrophotometry, objective color measurement in standard CIE and Munsell units using a color difference meter, and weight loss. The rate of metmyoglobin (Mb+) formation or browning increased with increasing temperature and air velocity. Low relative humidity, however, did not promote Mb+ formation. The lightness index of beef was highly correlated with water loss and initial pigment concentration. At high humidity and low air velocity, pigment oxidation was accelerated, and this may be attributed to stimulated bacterial growth under these conditions. Relative humidity near 90%, air velocity near 0.5 mps, and near freezing temperature appeared to represent the best environment for beef color maintenance. Consumers';perception of good beef color, as evaluated by a trained panel, showed that lower levels of Mb+ were tolerated when higher surface pigment concentrations were present and surface desiccation occurred. A regression equation showing the relationship between visual color scores and surface pigment concentration, extent of surface desiccation, and Mb+ concentration was developed. From the regression equation for Mb+ formation and desiccation rates as affected by storage conditions, color scores as a function of storage time can be predicted and storage conditions for color maintenance can be optimized.