Antimicrobial effects of corn zein films impregnated with nisin, lauric acid, and EDTA

Bacterial growth during food transport and storage is a problem that may be addressed with packaging materials that release antimicrobials during food contact. In a series of five experiments, EDTA, lauric acid (LA), nisin, a nd combinations of the three antimicrobial agents were incorporated into a corn zein film and exposed to broth cultures of Listeria monocytogenes and Salmonella Enteritidis for 48 h (sampled at 2, 4, 8, 12, 24, and 48 h). Fou r experiments used starting cultures of 10(8) CFU/ml in separate experiment s tested against each bacterium; the fifth experiment examined the inhibito ry effect of selected antimicrobial agents on Salmonella Enteritidis with a n initial inoculum of 10(4) CFU/ml. L. monocytogenes cell numbers decreased by greater than 4 logs after 48 h of exposure to films containing LA and n isin alone. No cells were detected for L. monocytogenes (8-log reduction) a fter 24-h exposure to any film combination that included LA. Of all film ag ent combinations tested, none had greater than a 1-log reduction of Salmone lla Enteritidis when a 10(8)-CFU/ml broth culture was used. When a 104 CFU/ ml of Salmonella Enteritidis initial inoculum was used, the films with EDTA and LA and EDTA, LA, and nisin were bacteriostatic. However, there was a 5 -log increase in cells exposed to control within 24 h. The results demonstr ate bacteriocidal and bacteriostatic activity of films containing antimicro bial agents.