Potassium Sorbate Does Not Increase Control of Listeria monocytogenes when Added to Zein Coatings with Nisin on the Surface of Full Fat Turkey Frankfurter Pieces in a Model System at 4°C

ABSTRACT: The antimicrobial effect of zein coatings containing nisin and potassium sorbate on turkey frankfurters against Listeria monocytogenes strain V7 at 4°C was determined. Our objectives were (1) to determine whether zein coatings with nisin and potassium sorbate alone or in combinations would reduce the growth of L. monocytogenes on turkey frankfurters at 4°C; (2) to determine the effect of zein, nisin, or potassium sorbate on L. monocytogenes after being challenged with high or low initial inoculum counts (log 6 or log 4); and (3) to determine whether potassium sorbate had any synergistic effect on the activity of nisin. Initial counts decreased for all the treatments containing nisin. Over 28 d, the nisin-alone treatment counts were lower than the control by 6.1 logs for the high inoculum. No cells were detected for the low inoculum test by day 21. The solvent controls (ethanol-glycerol or propylene glycol), yielded mean counts similar to those for zein-ethanol-glycerol or zein-propylene-glycol, giving 4 to 5 log lower counts versus the untreated controls at 28 d. Therefore zein per se had no antimicrobial activity. Use of 0.4% potassium sorbate did not significantly inhibit growth compared with the control or solvent-only controls. No significantly lower counts of L. monocytogenes were observed for zein-nisin coating treatments with sorbate versus without sorbate. Therefore, treatments using nisin alone or in combination with zein, ethanol-glycerol, or propylene glycol if approved for use on ready-to-eat foods, show promise for use as barriers against the growth of recontaminating, L. monocytogenes cells on this food substrate at 4°C.