Microbial Growth Patterns of Rehydrated Freeze‐Dried Foods. II. Chicken

SUMMARY Microbial growth patterns in rehydrated freeze‐dried chicken at 4, 20, 30, and 37°C are similar to those of rehydrated freeze‐dried shrimp, and are greatly influenced by storage temperature, time, and initial number of microorganisms present. Lag time was shortest at 37 and 30°C, four times as long at 20°C as at 37°C, and 120 times as long at 4°C as at 37°C. At 37°C, the maximum population was 300,000 times the initial population, while at 30°C it was 115,000 times wafter 26 hr. The microbial population increased 100,000‐fold at 55 hr at 20°C, and 500‐fold at 15 days at 4°C. A natural contaminant in the freeze‐dried chicken examined, eoagulase‐positive Staphylococcus aureus , was found to be at a level of 3040 organisms per gram, out of a total population of 10° organisms per gram. Fecal enterococci were also present in the freeze‐dried material at a level of about 10° to 10° per gram. Rehydration studies show that Staphylococcus aureus and “fecal enterococci” as natural contaminants in freeze‐dried chicken can grow in competition with the natural flora at 20 °C or above and that the competition may be due to the nature of the microbial distribution on the chicken surface. Refrigeration temperatures in the vicinity of 4°C completely suppressed the growth of S. aureus and greatly extended the shelf life of rehydrated chicken.