A newly published study by microbiologists at the University of Georgia in the USA has discovered that cells of the bacterial pathogen Salmonella are able to survive for much longer than expected in commercial food products with low water activities.
The researchers looked at cookie and cracker snack sandwich products containing a variety of low water activity (<0.40) chocolate-, peanut butter- and cheese-based fillings. These were inoculated with Salmonella cultures isolated from low moisture content foods implicated in foodborne disease outbreaks and then stored at 25oC for up to six months.
The bacteria survived longer in cookie sandwiches than cracker sandwiches and viable cells could still be recovered from chocolate and peanut butter crème fillings after six months incubation. According to study leader Professor Emeritus Larry Beuchat, “That was not expected.” Some survival was observed in all the products.
The study’s authors conclude that their results highlight the need to ensure that low moisture ingredients used for fillings in this type of product are not contaminated and that contamination does not occur during manufacture.
The study is published in the Journal of Food Protection and an abstract can be found here.