Development and characterization of an antimicrobial packaging film coating containing nisin for inhibition of Listeria monocytogenes

The purpose of this study was to develop and characterize a packaging film coating containing nisin. A spot-on-lawn assay was used to determine the effect of acid type (ascorbic, acetic, hydrochloric, lactic) and nisin level (equal increments from 10,000 IU to 9 IU) to be used in the formulation of the film coating. Zones of inhibition were measured after incubation on tryptic soy agar (37degreesC, 48 h). Low-density polyethylene films coated with differing levels of nisin were characterized by field emission scanning electron microscopy, tensile strength, elongation, and water vapor transmission rate. The MIC of nisin in solution was 157 mg/ml. All acids were equally inhibitory (P > 0.05), but acetic acid produced the largest zone of inhibition (21 mm). Field emission scanning electron microscopy confirmed that the cloudy appearance of the films was due to sodium chloride found in the commercially prepared nisin. Tensile strength increased as nisin concentration increased, which also corresponded to increasing film thickness. The nisin coatings (10,000 and 2,500 IU/ml) did not have a significant effect (P > 0.05) on the water vapor transmission rate of the low-density polyethylene film.