Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2008
Publication Date: 1/12/2009
Citation: Jin, Z.T., Zhang, H.Q., Sun, D., Su, J.Y., Sue, H. 2009. Antimicrobial Efficacy of Zinc Oxide Quantum Dots Against Listeria Monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7. Journal of Food Science. 74(1):M46-M52. Interpretive Summary: Outbreaks of food borne pathogens such as Escherichia coli, Salmonella and Listeria continue to draw public attention to food safety. There is a need to develop new antimicrobials to ensure food safety and extend shelf-life. Zinc oxide (ZnO) is one of five zinc compounds that are currently listed as generally recognized as safe by the U.S. Food and Drug Administration. Zinc salt has been used for the treatment of zinc deficiency in diets. However, the antimicrobial function of ZnO in foods has not been explored. In the present study, ZnO nanoparticles in the forms of ZnO powder, ZnO film and polyvinylprolidone capped ZnO (ZnO-PVP) were prepared and their antimicrobial activities in culture media and liquid foods were investigated. ZnO nanoparticles possess strong antimicrobial activities against Listeria monocytogenes, Salmonella Enteritidis and E. coli O157:H7 in culture media or liquid egg. Our results from this study demonstrated that the application of ZnO nanoparticles in food safety is promising.
Technical Abstract: Zinc oxide quantum dots (ZnO QDs) in a powder form, a ZnO-polystyrene (PS) film form and a polyvinylprolidone capped ZnO (ZnO-PVP) gel form were prepared and their antibacterial activities against foodborne pathogenic Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7 in culture media and liquid egg at 24 degree C or 4 degree C were investigated. ZnO QDs possess significant antimicrobial activities against all three pathogens in culture media or liquid egg. The inhibitory effects of ZnO were concentration dependent and also related to storage temperature and type of application. After 48 h incubation at 24 degree C, the cell populations of L. monocytogenes and E. coli O157:H7 in growth media with the presence of ZnO-PVP (3.2 mg ZnO/ml) were 3.7 and 3.0 log units/ml, respectively, whereas the controls had 9.0 log units. In liquid egg stored for 8 d at 24 degree C, Listeria and Salmonella cells in the controls increased from 3.8 to 7.2 and from 4.5 to 9.7 log units/ml, respectively, while the cells in the samples treated with 1.12 mg ZnO/ml were reduced to 1.4 log units for Listeria and 3.4 log units/ml for Salmonella. When stored at 4 degree C for 41 d, liquid egg samples with ZnO had 3 log units/ml of Salmonella cell, which is one log less than the initial cell counts, whereas the control had 7.4 log units/ml. Direct addition of ZnO-PVP exhibited stronger inhibitory effectiveness than direct addition of ZnO powder and ZnO-PVP coating. No antimicrobial activities of ZnO-PS film were observed. Our results from this study demonstrated that the application of ZnO nanoparticles in food safety is promising.