1. Evaluate the effectiveness of Pulsed Light (PL) on inactivation of pathogenic bacteria (Listeria monocytogenes, Escherichia coli 0157:H7) and non-pathogenic bacteria (Pseudomonas spp.) on the surface of cheeses with different physical characteristics, directly and through transparent polyethylene packaging. </P>
2. Design and evaluate the effectiveness of combination treatments (PL + selected antimicrobials on microbial inactivation of the selected challenge organisms </P>
3. Evaluate the effect of the most potent PL and combination treatments on the suppression of mold growth, under controlled temperature conditions. </P>
4. Evaluate the effect of the most potent PL and combination treatments on the quality and sensory properties of cheese.
To address current safety and quality challenges faced by the cheese industry, researchers designed an intervention strategy to inactivate contaminating pathogenic and spoilage microorganisms on the surface of cheese (blocks or slices). This strategy is based on Pulsed Light treatment, which is an FDA approved physical method for inactivating microbes, alone or in combination with approved antimicrobials, as a post?processing treatment of cheese surfaces. The results of this study will benefit both the consumer and cheese manufacturer by improving the safety of cheese and extending its shelf life. </P>Researchers have planned a series of experiments to achieve their goal. Their first experiment will generate PL inactivation data for selected challenge organisms (Listeria monocytogenes, E. coli O157:H7 and Pseudomonas fluorescens) that are inoculated on the surface of cheese (Cheddar, Swiss, and processed cheese). The inoculated surfaces will be exposed to PL at varying doses at refrigerated temperatures. PL will be applied directly on cheese and indirectly through polyethylene packaging. Their second experiment will evaluate the effect of antimicrobials (lactic acid, nisin, natamycin) at different doses, to enhance the effectiveness of PL treatments against the same challenge organisms. Their final experiments will evaluate the most potent PL and PL+ antimicrobial treatments to suppress mold growth under controlled temperature conditions and its effect on cheese quality (color, texture, and increase in temperature) and sensory properties.