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Survivability of Escherichia Coli in Commercial Powder Goat Milk during Four Months Storage at Two Different Temperatures

Brittany I Davis, Aftab Siddique, Ajit K Mahapatra and Young W Park

Bacteria in low moisture environments are not favorable for growth, but can survive and cause a possible food safety risk for consumers. A study was conducted to evaluate survivability of Escherichia coli and storage stability of commercial powdered goat milk (PGM) products. Three batches of whole milk PGM samples were purchased at a local outlet, and divided into two halves to assign non-inoculated control and E. coli inoculated groups, then stored at 4 and 22°C for 0, 2, and 4 months. Results showed that significant reduction (P<0.05) in E. coli counts occurred at 22°C treatment group by more than 2 log CFU/g at 2 months storage, then further decreased by an additional 0.37 log CFU/g at 4 months storage. The survival of E. coli was significantly higher at 4°C, suggesting that E. coli could survive better at 4°C by extending a longer latent period than at higher temperature (22°C) under the low water activity condition. E. coli counts had negative correlations with water activity at both temperature treatments for all three storage periods except for 0 and 2 months at 22°C, indicating that the survivability of the E. coli would decrease in powdered whole goat milk for 4 months of storage because of decrease in water activity. It was concluded that Escherichia coli survival and storage stability of the commercial PGM products were significantly (P<0.05) affected by storage temperature and time.