EFFECT OF TREATMENT CONDITIONS ON NISIN INACTIVATION OF GRAM-NEGATIVE BACTERIA

A method using nisin and a chelating agent to inactivate Salmonella species and other gram-negative bacteria has been developed. The objective of this study was to determine the effect of treatment conditions on the application of this method. Ten gram-negative organisms were used in this study, including six Salmonella species commonly associated with foodborne illness. Organisms were selected on the basis of sensitivity to nisin and a chelating agent. The following parameters were examined: (a) chelating agent, (b) nisin concentration, (c) incubation temperature, and (d) protein interference. Chelating agents included EDTA, ethylenebis (oxyethylene-nitrilo) tetraacetic acid, citric acid monohydrate, and sodium phosphate dibasic. The most effective treatment consisted of 50 to 100 mug/ml nisin applied in combination with 20 mM EDTA or citric acid monohydrate at a temperature range of 30 to 42-degrees-C. All of the chelators examined exhibited some inhibitory activity. The addition of bovine serum albumin to the treatments containing nisin and EDTA did not result in a significant decrease in inhibitory action.