Progress 10/01/03 to 09/30/06
Outputs
Antimicrobial packaging for food applications is a fairly new active packaging technology that has seen increased interest over the past decade. Methodology is available to assess the antimicrobial effectiveness of polymeric packaging materials, however activity quantification is based on diffusion of the antimicrobial away from the film or polymeric material in suspension. Standard methods that assess antimicrobial activity of films or sheets do not take into account biofilm development, which may render bacteria more resistant to antimicrobial properties of the test material; additionally, some antimicrobial films may function by preventing bacterial adhesion and biofilm development. The objective of our work was to identify and optimize in situ biofilm quantification methods and test them on commonly used food packaging materials of varying hydrophobicities. Packaging film hydrophobicity was quantified via contact angle. Pseudomonas aeruginosa was chosen as a model
organism to characterize biofilm growth on hydrophobic packaging materials. An enzyme linked lectin assay was used to monitor exopolysaccharide development over time. Fluorescent viability staining was used to quantify bacterial growth within the exopolysaccharide. For these techniques, packaging films were fixed to the bottom of a 96-well plate and a microwell plate reader used for in situ quantification. Direct epifluorescence microscopy was used to evaluate microbial populations within the biofilm. Preliminary results indicated a difference in biofilm and exopolysaccharide development between packaging films of different hydrophobicities. Methodologies were optimized to offer better in situ characterization of biofilms on hydrophobic packaging films.
Impacts
(N/A)
Publications
- Goddard, J. Hotchkiss, J.H. 2005. Surface analysis of food contact polymer films by contact angle. Institute of Food Technologists 2005 meeting (abstract).
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Progress 01/01/05 to 12/31/05
Outputs
Antimicrobial packaging for food applications is a fairly new active packaging technology that has seen increased interest over the past decade. Methodology is available to assess the antimicrobial effectiveness of polymeric packaging materials, however activity quantification is based on diffusion of the antimicrobial away from the film or polymeric material in suspension. Standard methods that assess antimicrobial activity of films or sheets do not take into account biofilm development, which may render bacteria more resistant to antimicrobial properties of the test material; additionally, some antimicrobial films may function by preventing bacterial adhesion and biofilm development. The objective of our work was to identify and optimize in situ biofilm quantification methods and test them on commonly used food packaging materials of varying hydrophobicities. Packaging film hydrophobicity was quantified via contact angle. Pseudomonas aeruginosa was chosen as a model
organism to characterize biofilm growth on hydrophobic packaging materials. An enzyme linked lectin assay was used to monitor exopolysaccharide development over time. Fluorescent viability staining was used to quantify bacterial growth within the exopolysaccharide. For these techniques, packaging films were fixed to the bottom of a 96-well plate and a microwell plate reader used for in situ quantification. Direct epifluorescence microscopy was used to evaluate microbial populations within the biofilm. Preliminary results indicated a difference in biofilm and exopolysaccharide development between packaging films of different hydrophobicities. Methodologies were optimized to offer better in situ characterization of biofilms on hydrophobic packaging films.
Impacts
(N/A)
Publications
- Goddard, J. Hotchkiss, J.H. 2005. Surface analysis of food contact polymer films by contact angle. Institute of Food Technologists 2005 meeting (abstract).
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Progress 01/01/04 to 12/31/04
Outputs
Bioactive synthetic polymers have great potential for application in food, biomedical and agricultural industries to improve product safety and quality. Antimicrobials approved for food use are typically added directly to the food product; by finding ways to incorporate these compounds directly into packaging materials, we can better control antimicrobial activity and limit levels ingested with the food. Many bioactive compounds, such as the lantibiotic nisin, are incompatible with food-contact polymers, preventing incorporation into commercial packaging materials. We are developing a general model using PEGylation to incorporate bioactive molecules such as nisin, other antimicrobial agents, and enzymes into synthetic polymers to improve product safety and quality. This model can be potentially used specifically to develop a food-grade persistent, continuous acting nisin-based antimicrobial synthetic polymer that can be readily used as effective food contact
processing surfaces and potentially further applied as packaging materials to control Listeria monocytogenes contamination in RTE meat and poultry products. Our research objectives were to synthesize a polyethylene glycol/nisin (PEG/nisin) conjugate that may be used as a nonpolar antimicrobial polymer additive to increase nisin compatibility with synthetic polymers. The chemical and physical characteristics of the PEG/nisin conjugate were measured as well as the antimicrobial activity towards L. monocytogenes. We purified nisin from its commercially available form, Nisaplin, using size exclusion filtration and reverse phase HPLC; protein yield was measured using the Bradford Method, and the antimicrobial activity of the purified form was measured using growth inhibition studies. Mono-PEGylation of nisin was performed using mPEG propionaldehyde, an activated form of PEG, and sodium cyanoborohydride, a reducing agent. Derivitization targeted the N-terminal alpha amino group of nisin,
under acidic and aqueous conditions. The degree of PEGylation was assessed by HPLC and MALDI-TOF analysis. PEGylated nisin was tested for antimicrobial activity. PEGylation was achieved, however with a significant loss in antimicrobial activity. Alternative derivitization methods targeting different sites on the nisin molecule under different conditions are being investigated to improve retention of antimicrobial activity.
Impacts
Initial investigations to develop a bioactive molecule polymer incorporation model indicate that while the tested methodology was successful in producing a synthetic polymer compatible antimicrobial conjugate, modifications to the method should be investigated to improve antimicrobial activity retention. The conjugation method used shows promise for other bioactive molecules, which we are investigating further.
Publications
- Cavalcante, JA. 2004. MS Thesis: Mono-Pegylation of the lantibioic nisin. Food Science, Cornell University.
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