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This project addresses the priority "Development of knowledge and control of formation of novel nanoparticles, nanostructures and systems that can effectively enhance food safety and biosecurity" of the USDA AFRI Program A1511 Nanoscale Science and Nanotechnology to Ensure Safe Food. <P> The long-term project goal is to develop practical nanoscale antimicrobial delivery systems (NADS) for use in food matrices for enhanced antimicrobial efficacy and improved quality. In this proposal, we propose to prepare capsules of lipophilic antimicrobials (plant essential oil components) by spray-drying emulsions with a hexane-oil phase containing antimicrobials and whey protein or its conjugate with maltodextrin as a surfactant. <P>We have demonstrated that transparent nanodispersions of 5% thymol-loaded capsules maintained visual clarity after heating at a wide range of solvent conditions and effectively inactivated Escherichia coli O157:H7 (8 log CFU/mL). <P>In this multi-institutional project, we propose to continue to develop and characterize this class of promising NADS via these objectives: <OL> <LI> Physicochemical properties of NADS as affected by preparation conditions<LI> In vitro antimicrobial efficacy of NADS against pathogenic bacteria in growth media<LI> Antimicrobial efficacy of NADS in food matrices and the impacts on quality. </OL> Completion of our research objectives will demonstrate the antimicrobial capabilities of this novel group of NADS against E. coli O157:H7, Salmonella, and Listeria monocytogenes in the food matrices of fluid milk, unpasteurized fresh apple cider and ground beef. The project may provide solutions to reduce/eliminate outbreaks of foodborne illness to supply safe, high-quality foods in the US and beyond.
NON-TECHNICAL SUMMARY: Continued outbreaks and sporadic cases of foodborne illness caused by bacterial pathogen such as Escherichia coli O157:H7, Salmonella, Listeria monocytogenes have continued to put food safety in a negative spotlight. There are multiple causes for these foodborne illnesses including cross-contamination, insufficient thermal processes to inactivate pathogens or post-process contamination. For example, E. coli O157:H7 is a "zero-tolerance" bacterium in ground beef and has led to many recalls because, even though the product is cooked, uneven heating may not completely inactivate the pathogen. At the same time consumers want improved microbiological safety, they are also demanding fresher, minimally processed products and products with "natural" ingredients. Even though novel processing technologies have been developed and studied, many require adjunct preservation systems to function more efficiently or to prevent growth of surviving microorganisms during storage. A very efficient intervention strategy involves the addition of generally-recognized-as-safe or natural antimicrobials into food systems. Because many antimicrobials are only marginally water soluble or insoluble in water, this project develops technology and knowledge of nanometer-sized structures that disperse antimicrobials in food systems to enhance their efficacy without negatively impacting or ideally improving the quality of corresponding foods. These nanostructures are based on high-quality food proteins and carbohydrates and have promise to improve healthfulness, safety, and quality of various food products.
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APPROACH: In the first objective, emulsions will be prepared by manipulating properties of dispersed phase and surfactants. Single or multiple essential oil components will be dissolved in the oil phase with different ratios of volatile hexane and non-volatile soybean oil that may impact the encapsulation efficiency, particle size, and possibly release kinetics. Conjugates will be prepared from different ratios of WPI and maltodextrin with various chain lengths. Physicochemical properties of NADS will be characterized for spray-dried powders and their dispersions. This will include a series of characterizations to illustrate structure, viscosity, visual clarity, thermal stability, loading levels, storage stability, etc. of dispersions of NADS. In the second objective, antimicrobial properties of NADS and their controls will be characterized using various strains of E. coli O157:H7, Salmonella, and L. monocytogenes. Combination of nisin, lysozyme, and NADS will also be studied for selected treatments. In the third objective, NADS will be incorporated in real food matrices to test their antimicrobial functions and their impacts on physical properties and quality, including sensory properties.