Integration of Bioactives for Food Safety/Quality Enhancement and Discovery

NON-TECHNICAL SUMMARY: The proposed research will address the safety and quality of food. This not only includes preventing food deterioration but also enhancing the composition of food during storage through "enhancer coatings." Specific strategies will include 1. active packaging (antimicrobial, antioxidant, bioactive), 2. novel processing (non-thermal plasma, thermal (heat and cold) in combination with biocides), 3. evaluate variables of foods, films, antimicrobials and surfaces affecting transfer and/or survival of bacteria through an undergraduate creative inquiry research team. 1.Two main research tracts will be taken toward furthering active packaging of food. The use of natural antimicrobials and antioxidants to extend the shelf life of meat products will be used primarily focusing on bio-based films and coatings. These coatings include. lactic acid carriers that modify the metabolic pathway of bacteria. Another research area for active packaging will be the use of coatings carrying natural phenolic compounds to both extend the shelf life of fruits and vegetables while also enhancing the production and preservation of natural phenolic antioxidants produced in the stored fruit or vegetable during storage. 2.Surface inactivation of pathogenic and spoilage bacteria will be accomplished using novel methods and combination of traditional methods. One method will be non-thermal plasmas which will minimize food quality changes while inactivating target bacterial. Using heat and cold as processing treatments and combining these with biocides in a hurdle concept will be tested and include statistical modeling of these techniques. 3.Creative Inquiry undergraduate teams will investigate various food safety topics that focus on food surfaces. These include practical topics such as food contact transfer of bacteria on various surfaces including food surfaces, elimination of bacteria from food and other surfaces using commercial household treatments, and the effects of common practices on bacterial transfer. <P> APPROACH: 1. Active Packaging: The use of natural antimicrobials and antioxidants to extend the shelf life of meat products will be used primarily focusing on bio-based films and coatings. These coatings include lactic acid carriers that modify the metabolic pathway of bacteria. Another research area for active packaging will be the use of coatings carrying natural phenolic compounds to both extend the shelf life of fruits and vegetables while also enhancing the production and preservation of natural phenolic antioxidants produced in the stored fruit or vegetable during storage. The film materials will 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 samples will be placed on a agar surface 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. 2. Novel Processing: Surface inactivation of pathogenic and spoilage bacteria will be accomplished using novel methods and combination of traditional methods. One method will be non-thermal plasmas which will minimize food quality changes while inactivating target bacterial. Using heat and cold as processing treatments and combining these with biocides in a hurdle concept will be tested and include statistical modeling of these techniques. The objective will be to determine the mode of action (e.g., cell membrane degradation, cell leakage, and intracellular disruption) by indicated plasma species (O-, -OH, O3, NO, and CO) alone and in combination. Using an ANEP system, in conjunction with Dr. Kevin Keener from Purdue University, known modes of bacterial inactivation (e.g., cell membrane degradation, cell leakage, and intracellular disruption) will be examined. Experimental methods will be developed by studying the three modes of bacterial inactivation individually for three food pathogens (Salmonella spp., E. coli O157:H7, and Listeria monocytogenes) inoculated on simulated food and fresh spinach. Three modes of inactivation being studied are: 1) Oxidation of the cell membrane 2) Leakage of intracellular components 3) Disruption of cellular processes To assess cell membrane damage, plasma-treated cells will be incubated with propidium iodide which is a nucleotide-binding probe. The degree of binding of this probe will be determined by measuring fluorescence intensity compared to untreated cells. The relative fluorescence intensity is directly related to cell membrane damage. Cell membrane damage will be further investigated using fluorescence microscopy. Briefly, cells will be stained with red and green nucleic acid stains (propidium iodide and SYTO 9 Molecular ProbesT, respectively) then examined under a fluorescence microscope. The green dye attaches to the membrane of all bacterial membranes while the red dye penetrates only damaged cells while reducing green dye binding when dyes are mixed.