Effect of Thaw Conditions on Ground Beef ¹

Three sampling periods were selected to acquire ground beef packages from two retail stores. Initially, samples were subjectively evaluated for color and overall appearance. Microbial load and taxonomy were determined and the samples were subsequently frozen. After frozen storage, one-half of the packages were thawed at 5 C for 4, 8, 24, 48 and 72 h, whereas the other samples were thawed at 25 C for the same periods. After thawing, samples were evaluated for the same characteristics as before freezing. Samples from each treatment were also evaluated for flavor, odor and overall acceptability. Appearance traits, taste and microbial load were affected (P < .05) by thaw time and temperature. Major groups of bacteria identified were: micrococci, Pseudomonas , streptococci, staphylococci, Flavobacterium , lactobacilli and coliforms. Salmonella and pathogenic Staphylococcus were not found. Those microorganisms which were identified were considered to be responsible for deterioration of appearance and taste attributes. Increased coliform growth at 25 C, especially after 8 h, suggests a need to thaw ground beef at refrigerated temperature to reduce public health concern. Results suggest that a proper thaw time and temperature to maintain acceptable appearance and taste of ground beef would be 24 h or less at refrigerated temperature.