In 2009 when PCA was distributing Salmonella-contaminated peanut paste products to lots of manufacturers, many were asking questions about how the pathogen survived in the low-moisture environment and whether the outbreak was an indicator that the snack food industry was facing a larger issue. Since then there have been numerous low-moisture food outbreaks (here’s a nice review from Sofia Santillana Farakos and Joe Franks).
Friends of barfblog Larry Beuchat (right, exactly as shown) and Scott Burnett did some work on peanut butter and Salmonella and showed that the pathogen could survive for a long, long time, ‘Post-process contamination of peanut butter and spreads with Salmonella may to result in survival in these products for the duration of their shelf life at 5 degrees C and possibly 21 degrees C, depending on the formulation.’
Larry has published another great paper on Salmonella in low moisture foods, Survival of Salmonella in Cookie and Cracker Sandwiches Containing Inoculated, Low-Water Activity Fillings in JFP. From the abstract, ‘The ability of Salmonella to survive for at least 182 days in fillings of cookie and cracker sandwiches demonstrates a need to assure that filling ingredients do not contain the pathogen and that contamination does not occur during manufacture.’
Or in his own words,
“There have been an increased number of outbreaks of diseases associated with consumption of contaminated dry foods. We wouldn’t expect salmonella to grow in foods that have a very dry environment,” said Beuchat, who works with the Center for Food Safety on the UGA campus in Griffin.
Focusing on cookie and cracker sandwiches, the researchers put the salmonella into four types of fillings found in cookies or crackers and placed them into storage. The researchers used cheese and peanut butter fillings for the cracker sandwiches and chocolate and vanilla fillings for the cookie sandwiches.
These “are the kind that we find in grocery stores or vending machines,” Beuchat said.
“The salmonella didn’t survive as well in the cracker sandwiches as it did in the cookie sandwiches,” Beuchat said.
In some cases, the pathogen was able to survive for at least to six months in the sandwiches.“That was not expected,” he said.