The Role of Catalase and Pyruvate on the Recovery of Cold - Shocked Bacteria

The study principally aimed at evaluating different additives to the culture medium for the recovery of cold-shocked bacteria isolated from chilled carcasses. Sixty randomly selected beef carcasses were assigned for investigation from which 630 swabs were collected for assessment of microbiological contamination of carcasses during the processes after skinning and evisceration, along the washing to the chilling stage. Obtained results were analysed by statistical package (SAS 2000, version 9.0) and revealed bacterial counts decreased significantly (p≤0.05) from skinning to chilling (3.67±0.0 to 1.23±0.10, p≤0.01). The predominant bacteria isolated from the carcasses were Staphylococcus spp. followed by Enterobacteriaceae and Pseudomonas spp. To test for recovery of cold-shocked bacteria, the bacterial load as CFU was evaluated after treatments with catalase, pyruvate and their combination. The CFU of samples from chilled carcasses increased after treatment with catalase and pyruvate (1.23±0.52 vs. 2.54±0.12 and 2.42±0.33, respectively; p≤0.05). The results showed that catalase treatment has induced higher bacterial recovery compared to pyruvate alone or the combination of pyruvate and catalase, but the bacteria died when the concentration of catalase and pyruvate was increased. Addition of catalase or pyruvate to plate count agar medium gives true estimates of the bacterial load of chilled carcasses and other cold foods.