Evaluation of chemical additives for the separation and recovery of bacteria from food matrices

The microbiological testing of foods is a well-established science. Due to the severity of foodborne pathogen illnesses, the widespread use and implementation of rapid detection methods in food testing labs is increasingly important. The first step for successful testing is sampling. Surfactants have been widely used in food microbiology, but there is not much, if any, published research about the use of fatty alcohols and chemical dispersants as aids in microbial separation and recovery. The microbial extraction efficiency of Escherichia coli K12 and Listeria innocua from three representative food matrices (hot dogs, spinach, and milk) was measured using chemical additives (surfactants, fatty alcohols, and a chemical dispersant) at three concentrations, each in a buffered solution. The food matrices were inoculated with a known amount of bacteria, blended in a buffer solution, with and without additives, and then centrifuged. Data were analyzed through selective media plate counts. Results showed that Tween 80 at 0.01% was found to be the most effective additive for microbial recovery from each food matrix examined. However, the addition of fatty alcohols to surfactants significantly aided in separation and recovery, and should be further studied.