Application of Nanotechnology, Antimicrobial, and Polymer Films in Food Safety and Quality

NON-TECHNICAL SUMMARY: The rapid detection of toxic food agents and the development of strategies to reduce their presence in food are problems that need to be addresed to improve the safety of the food and water supply. This project will utilize nanotechnolgy to develop rapid and simple biosensors to detect the presence of inetntional and ubiquitous toxic agenst in food and water. Additionally, active films will be developed to reduce the risk from these toxic agents by using naturla materials. <P>APPROACH:<BR> 1. The basic concept is to attach specific antibodies that will link to target bacterial pathogens to nanoparticles in the size range of 100 to 500 nm in diameter. The nanoparticles will possess luminescent properties and contain a small amount of iron embedded in the particle. Various methods will be evaluated for attaching the antibody to the nanoparticles and this procedure will be optimized for retention of antibody activity and secure binding of the antibody to the particle.<BR> 2. The incorporation of biocides, including nisin, lysozyme, and EDTA, into protein and polymer packaging films will be performed using a heat-press method developed at Clemson University in cooperation between the Food Science/Human Nutrition and Chemical Engineering Departments. In this process, the film components are mixed in the dry form then melted into a film material under heat and pressure. The melt temperature varies depending upon the raw film material being used. Materials that will be used include soy and corn protein, and common polymer film materials such as ethylene and styrene. The film material will then be tested for its efficacy in reducing bacterial pathogens using both a zone of inhibition assay and log reduction method. For the zone assay an 8 mm diameter film sample will be placed on a bacterial lawn inoculated with a Listeria monocytogenes, a nonpathogenic strain of Esherichia coli, or a nalidixic acid resistant strain of Salmonella typhimurium or Salmonella enteriditis then the clear zone of inhibition will be measured after incubation. Similarly, an 8-cm diameter film sample will be placed in a sterile petri dish and covered with 15 ml of broth containing the above same organisms used in the zone test.<BR> 3. Development of biopolymer film applications for foods will also be a collaborative project with Drs Acton and Ogale. Alteration of film physical properties including strength, elasticity, permeability and moisture absorption will be tested by changing the composition and/or the processing parameters of the film. The use of lower cost soy and wheat flour and the addition of fats, waxes, and emulsifiers will be included. The thermal compaction method will be employed as this is more environmentally friendly then casting. The continuous thermal extrusion will also be developed for the mass production of these films. Testing will include conventional physical tests, permeability tests, and shelf life tests for the films stored for 6-12 months under various temperature and relative humidity.
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PROGRESS: 2003/07 TO 2008/06<BR>
OUTPUTS: Listeria monocytogenes is a gram-positive pathogen frequently involved in outbreaks of foodborne disease. The natural (generally recognized as safe) and inexpensive qualities of lysozyme make it a widely used food preservative for controlling foodborne pathogens. However, its efficacy against pathogens may be reduced by the undesirable interactions with food components and non-target bacteria. Nanoparticles functionalized with pathogen-specific antibodies (immunonanoparticles) may serve as a carrier of natural antimicrobials to target the specific pathogen and improve the stability of antimicrobials in foods. The objective of this research was to study the antimicrobial activity of lysozyme absorbed on immunonanoparticles against L. monocytogenes Scott A. Polystyrene nanoparticles with active carboxyl groups were conjugated with anti-L. monocytogenes through covalent bounding. Immunonanoparticles were then coated with lysozyme by direct adsorption. The antimicrobial activity of lysozyme adsorbed on immunonanoparticles was compared to that of free lysozyme in phosphate buffered saline. Several factors, such as the amount of anti-L. monocytogenes and lysozyme, and the adsorption time, were optimized for the most efficient inhibition. A modified Lowry method was used to quantify the lysozyme adsorbed on immunonanoparticles. Nanoparticles were conjugated with 0.04 ug anti-L. monocytogenes per ml, and at that concentration, immunonanoparticles demonstrated enhanced antimicrobial activities of lysozyme. Lysozyme 350 ug adsorbed on immunonanoparticles reduced the L. monocytogenes Scott A population from 5.2 log CFU/ml to below the detection limit in 3 h. However, when free lysozyme 500 ug/ml was used, ca. 2.2 log CFU/ml of the L. monocytogenes Scott A remained culturable after 5 h treatment. Our study revealed that the use of immunonanoparticles coated with lysozyme is a more efficient method than direct addition of lysozyme in inhibiting L. monocytogenes. Antimicrobial coatings were developed using gelatin and commercial nisin mixtures. In the liquid system, all square nisin films showed 3 log reduction by one hour except control. At 4 hours, there was no detected L. monocytogenes in the peptone solution containing 4.5mg, 9.2mg, 16.3mg and 24.4mg of nisin. At 6 and 8 hours, every nisin film inhibited L. monocytogenes completely. In the solid system, each circular nisin films included 0.04mg, 0.09mg, 0.16mg and 0.23mg of nisin showed positive effect against L. monocytogenes. However, the activity of 0.04mg circular nisin film was very weak compared to other positive films. <P>
IMPACT: 2003/07 TO 2008/06<BR>
The objective of this research was the development of active films to enhance the safety and quality of food. Peer reviewed publications, trade journal articles, book chapters and presentation have contributed to the goals of this project.