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Currently, there is a critical need for low energy and mild technologies that can improve microbial safety reliably in minimally processed foods such as fresh produce. In this study, we envision the development of a nanoparticle wash treatment with the capability of significantly reducing or eliminating pathogenic bacteria associated with fresh or fresh-cut fruits and vegetables. <P>The project objectives address the priorites of the program, "Nanoscale Science and Nanotechnology to Ensure Safe Food," focusing on novel nanotechnology mitigation measures in minimally processed foods. The specific tasks of the proposed program are: <OL> <LI>Design, synthesis and characterization of ultra-potent chitosan nanoparticles coated by antimicrobial peptides (e.g. nisin) ("green particles"). <LI> Evaluation of peptide-enhanced nanoparticles as a lysis agent in realistic food processing environments (neutral to acidic pH, low to moderate temperature, salts or lipids present). <LI>Development of a post-harvest nanoparticle-electric field treatment for decreasing the bacterial load of fresh cut leafy greens and tomatoes (improving safety and prolonging shelf life). </OL>Our study can provide guidelines for combining mild, biocompatible and energy efficient food safety methods synergistically in the design of a "green" nanoparticle treatment step for improved safety of minimally processed fruits and vegetables.
Non-Technical Summary: Recent outbreaks of pathogenic bacteria contaminating widely consumed produce have been reported in the national media, with Escherichia coli O157:H7 and Salmonella among the leading pathogenic threats to food safety. Thermal treatments are not appropriate for fresh produce, and large scale irradiation is limited by cost. In response, we aim to develop a nanoparticle wash treatment with the capability of significantly reducing pathogenic bacteria associated with fresh or fresh-cut fruits and vegetables, and which may be applied synergistically with a conventional chlorine wash. The success of such a treatment depends on improved understanding of nanoparticle-bacteria interactions. The high potency of the nanoparticles derives from the combination of high positive charge, antimicrobial peptide molecules attached on the surface, antimicrobial proteins encapsulated inside, and enhanced activity under applied electric fields. The proposed nanoparticle wash is a "green technology" because it utilizes edible and naturally abundant materials, and has low environmental impact compared with the conventional chlorine wash. The research involves design, production and characterization of the enhanced nanoparticles, testing of the wash treatment in realistic food processing environments, and application to fresh cut leafy greens and tomatoes. Our study can provide guidelines for combining mild, biocompatible and energy efficient food safety methods synergistically in the design of a "green" nanoparticle treatment step for improved safety of minimally processed fruits and vegetables. <P> Approach: We aim to develop a nanoparticle wash treatment with the capability of significantly reducing or eliminating pathogenic bacteria associated with fresh or fresh-cut fruits and vegetables. The proposed treatment will employ suspensions of cationic, preservative-loaded, antimicrobial peptide-decorated nanoparticles, where washing or immersion in a nanoparticle suspension, possibly in conjunction with the application of a mild electric field, can flocculate and destroy pathogenic bacteria on fresh produce immediately prior to packaging. Ultra-potent, peptide-enhanced nanoparticles combine the synergistic action of cationic chitosan nanoparticles, encapsulated lysozyme, surface-attached nisin and applied electric fields on the bacterial cell membrane, and consist only of GRAS materials. The major pathogen targets of this study are Escherichia coli O157:H7 and Salmonella Typhimurium (Gram-negative bacteria) and Listeria monocytogenes (Gram-positive bacteria). The novelty of the proposed research centers on the effective delivery of multiple antimicrobials which are required to positively eliminate both Gram-positive and Gram-negative foodborne pathogens. The project investigators form a versatile team for tackling a challenging interdisciplinary problem, combining complementary strengths in microencapsulation, imaging, biodetection, microfluidics, polymer chemistry, surface science, food science and microbiology.