|WANG, JIAMEI - Nanjing Agricultural University
|Hinton Jr, Arthur
|ZHANG, JIANHAO - Nanjing Agricultural University
Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2014
Publication Date: 7/7/2014
Citation: Wang, J., Zhuang, H., Hinton Jr, A., Bowker, B.C., Zhang, J. 2014. Photocatalytic disinfection of spoilage bacteria Pseudomonas fluorescens and Macrococcus caseolyticus by nano-TiO2. LWT - Food Science and Technology. 59:1009-1017.
Interpretive Summary: Because of trends in healthy eating nowadays, per capita consumption of poultry meat in the U.S.A. has increased dramatically. However, fresh poultry meat is very perishable and its shelf life could be as short as 5 days at a refrigerated temperature due to microbial growth. Many interventions have been used or tested to control microbial growth and extend shelf life of poultry meat products at refrigerated temperatures. However, most of them are applied during poultry processing and cannot prevent the products from microbial contamination after processing. Metal oxide TiO2 has been considered as GRAS, has been demonstrate to be very effective to inhibit microbial growth under UV light, and could be developed for control of microbial growth after meat has been packed in trays or bags. The objective of this study was to investigate the antimicrobial effects of nano-TiO2 particles on spoilage bacteria isolated from chicken carcasses. Our results show that nano-TiO2 effectively inhibited the growth of spoilage microbes in fresh poultry meat. Its effectiveness could be affected by nano-TiO2 concentrations, initial microbial populations, and intensity of UV light. Under UV light, nano-TiO2 attacked bacterial cells and resulted in oxidation of cell membranes and damage of cell integrity, thereafter, causing cell death. These results demonstrate that we may make antimicrobial packaging systems with nano-TiO2 to effectively control growth of spoilage microbes and extend shelf life of fresh poultry meat products.
Technical Abstract: Photocatalytic disinfection of spoilage bacteria gram-negative (G-) P. fluorescens and gram-positive (G+) M. caseolyticus by nano-TiO2 under different experimental conditions and the disinfection mechanism were investigated. The experimental conditions included the initial bacterial populations, nano-TiO2 content, and light intensity. The disinfection mechanism was determined by the release of cellular K+, lipid oxidation, and the TEM morphological images. Photocatalytic treatments showed similar effects on both G- and G+ bacteria regardless of experimental conditions and mechanism measurements. The lower the initial bacterial populations, the shorter the time was required to eliminate the bacteria. Increased TiO2 contents and light intensity resulted in increased bacterial killing. Both K+ leakage and lipid oxidation increased significantly after treatment. Electronic images illustrate that bacterial cells started showing damages in cell walls and cell membranes after 30min treatment, cytoplasm leakage after 90min treatment, and lysis after 150min treatment. The greater reduction was observed in M. caseolyticus population than that in P. fluorescens population. These results demonstrate that nano-TiO2 is very effective against both G- and G+ spoilage bacteria under light. G+ spoilage bacterium M. caseolyticus is more susceptible to photocatalytic disinfection by nano-TiO2 under light than G- spoilage bacterium P. fluorescens.