Survival and growth characteristics of Escherichia coli O157:H7 in pasteurized and unpasteurized Cheddar cheese whey.
The objective of this study was to determine the survival and growth characteristics of Escherichia coli O157:H7 in whey. A five-strain mixture of E. coli O157:H7 was inoculated into 100 ml of fresh, pasteurized or unpasteurized Cheddar cheese whey (pH 5.5) at 10(5) or 10(2) CFU/ml, and stored at 4, 10 or 15 degrees C. The population of E. coli O157:H7 (on Sorbitol MacConkey agar supplemented with 0.1% 4-methylumbelliferyl-beta-D-glucuronide) and lactic acid bacteria (on All Purpose Tween agar) were determined on days 0, 1, 4, 7, 14, 21 and 28. At all storage temperatures, survival of E. coli O157:H7 was significantly higher (P<0.01) in the pasteurized whey compared to that in the unpasteurized samples. At 10 and 15 degrees C, E. coli O157:H7 in pasteurized whey significantly (P<0.05) increased during the first week of storage, followed by a decrease thereafter. However at the same temperatures, E. coli O157:H7 exhibited a steady decline in the unpasteurized samples from day 0. At 4 degrees C, E. coli O157:H7 did not grow in pasteurized and unpasteurized whey; however, the pathogen persisted longer in pasteurized samples. At all the three storage temperatures, E. coli O157:H7 survived up to day 21 in the pasteurized and unpasteurized whey. The initial load of lactic acid bacteria in the unpasteurized whey samples was approximately 7.0 log10 CFU/ml and, by day 28, greater than 3.0 log10 CFU/ml of lactic acid bacteria survived in unpasteurized whey at all temperatures, with the highest counts recovered at 4 degrees C. Results indicate the potential risk of persistence of E. coli O157:H7 in whey in the event of contamination with this pathogen.
Marek
Patrick
P
Department of Animal Science, Unit-40, University of Connecticut, 3636 Horsebarn Hill Road Extension, Storrs 06269, USA.
Nair
Manoj Kumar Mohan
MK
Hoagland
Thomas
T
Venkitanarayanan
Kumar
K
D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development*; D005516:Food Microbiology; D005519:Food Preservation; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000254:growth & development*; D008894:Milk Proteins; D013696:Temperature; D013997:Time Factors; D000067816:Whey Proteins
D008894:Milk Proteins; D000067816:Whey Proteins