Salmonella contamination can grow on blueberries – unlike strawberries – when harvested at or near full ripeness and cooled at retail display temperatures, a study by University of Florida researchers finds.
The study in July"s Journal of Food Protection compares the fate of salmonella and E. coli O157:H7 on bruised and intact surfaces of both berries at shipping as well as retail temperatures.
It finds E. coli populations decline at both temperatures, roughly equal to 35.6 degrees Fahrenheit for shipping and 60 for retail.
The same holds true of strawberries inoculated with salmonella. But on blueberries the pathogen, after an initial decline, grew back to levels near or above initial amounts over a seven-day period.
The study found no significant difference between bruised and intact surfaces or between two maturity levels. Ripe fruit is more vulnerable to bruising during harvest and transport.
The strawberries were subjected to modified atmospheres. Those did not affect the behavior of E. coli O157:H7 and salmonella on contaminated strawberries at either temperature, according to the researchers.
The study authors are Michelle Danyluk, Loretta Friedrich and Thao Nguyen of the university"s Citrus Research and Education Center.