Control of Listeria monocytogenes on Turkey Frankfurters by Generally-Recognized-as-Safe Preservatives

Abstract

Generally-recognized-as-safe chemicals applied to the surfaces of turkey frankfurters were evaluated for their ability to reduce populations of or inhibit the growth of Listeria monocytogenes. Frankfurters were treated prior to inoculation by dipping for 1 min in a solution of one of four preservatives (sodium benzoate, sodium propionate, potassium sorbate, and sodium diacetate) at three different concentrations (15, 20, and 25% [wt/vol]), with <0.3% of the preservative being present for each frankfurter. Subsequently, 0.1 ml of a five-strain mixture of L. monocytogenes (106 CFU/ml) was used to surface inoculate each frankfurter separately in a sterile stomacher bag. Inoculated frankfurter bags were held at 4, 13, and 22°C, and L. monocytogenes cells were enumerated at 0, 3, 7, 10, and 14 days of storage. The results of this study revealed that at all three concentrations of all four preservatives, the initial populations of L. monocytogenes decreased immediately by 1 to 2 log10 CFU/g. After 14 days of storage at 4°C, L. monocytogenes counts for all treated frankfurters were 3 to 4 log10 CFU/g less than those for the untreated frankfurters. After 14 days of storage at 13°C, L. monocytogenes counts for frankfurters treated with 25% sodium benzoate or 25% sodium diacetate were 3.5 to 4.5 log10 CFU/g less than those for untreated frankfurters, and those for frankfurters treated with 25% sodium propionate or 25% potassium sorbate were 2.5 log10 CFU/g less than those for untreated frankfurters. In all instances, the degree of growth inhibition was directly proportional to the concentration of the preservative. Only frankfurters treated with 25% sodium diacetate or sodium benzoate were significantly inhibitory to L. monocytogenes when held at 22°C for 7 days or longer. Interestingly, the untreated frankfurters held at 22°C were spoiled within 7 days, with copious slime formation, whereas there was no evidence of slime on any treated frankfurters after 14 days of storage.