Title: Antimicrobial activity of nisin and lactic acid incorporated polylactic acid films against Listeria monocytogenes and Escherichia coli O157:H7 Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 21, 2007
Publication Date: July 31, 2007
Citation: Jin, Z.T., Zhang, H.Q. 2007. Antimicrobial activity of nisin and lactic acid incorporated polylactic acid films against Listeria monocytogenes and Escherichia coli O157:H7 [abstract]. International Food Technologists Annual Meeting. Paper No. 206-03. p. 292. Technical Abstract: Justification Outbreaks of food borne pathogens such as Escherichia coli O157:H7 and Listeria monocytogenes continue to draw public attention to food safety. Additional intervention hurdle such as antimicrobial packaging is needed for controlling food borne pathogens in packaged food products. Objective The objective of this study was to investigate the effectiveness of nisin and lactic acid (LA) incorporated polylactic acid (PLA) films against pathogens. Methods Nisin mixed with PLA granules with/without LA and were cast into films by a solvent casting method. Each PLA film (157 square cm total surface area, 0.1~0.2 mm average thickness) contains 1 g PLA, 12.5 mg nisin and/or 1 g LA. Growth curves of L. monocytogenes in brain-heart infusion broth (BHIB) and E. coli O157:H7 in tryptic soy broth (TSB) were determined at room temperature. Inhibition tests were also performed in liquid egg white and orange juice. The maximum concentration of nisin and LA released to liquid media was equivalent to 200 IU/ml and 1.9 mg/ml, respectively. Results The films incorporated with nisin significantly inhibited the growth of L. monocytogenes. LA in PLA+nisin films significantly increased the effectiveness of inhibition of L. monocytogenes. A 5-log reduction of L.monocytogenes in liquid egg white and a 3-log reduction of L.monocytogenes in orange juice were achieved by Nisin+LA PLA films. Nisin PLA film did not alter the growth of E. coli O157:H7. However, Nisn + LA PLA film slowed down the growth of E. coli O157:H7 in TSB and achieved 3.5-log reduction of E. coli O157:H7 in orange juice. Significance This study demonstrated that lactic acid significantly enhances the antimicrobial functionality of nisin in PLA films. The use of biodegradable PLA films with the combination of nisin and LA may be further developed into an environmentally friendly antimicrobial food packaging material.