An official website of the United States government.
This study investigates the feasibility of sequentially applying sanitation technologies - vacuum, gaseous ozone, and pressurized gases - to leafy green produce to overcome external and internal contamination with E. coli O157:H7. The development of this approach involves: <ol>
<li> adapting existing vacuum-cooling technology for freshly harvested produce to include a sanitization step involving repressurization with gaseous ozone;
<li> determining the kinetics of E. coli O157:H7 inactivation in leafy green produce in relation to the treatment variables; and
<li> monitoring the viability of E. coli O157:H7 during ozone treatment and refrigerated storage of fresh produce.</ol>
Ozone is a potent sanitizer that is well-suited for use with fresh produce. Results of this project may provide the fresh produce industry with a critical decontamination step that can be incorporated into exiting production and processing lines, potentially reducing the health risks associated with sporadic contamination of fresh produce with E. coli O157:H7.
<p>
The preliminary experiments will involve the use of an elaborate ozone treatment vessel located in the investigators\' biosafety level-2 facility. Processing variables to be tested include: vacuum level; vessel pressure after ozone introduction; ozone concentration; treatment time; average temperature; and product loading. Preliminary studies will be conducted on diffusion of ozone into various locations within the treatment chamber. A sampling manifold will be installed to draw gas samples from multiple locations when different product loads are tested. Product/vessel volume ratio will be optimized to make sure all leaves are exposed to the sanitizer. If needed, a slow tumbling of the product within the vessel during the treatment will be applied. In all cases, E. coli O157:H7 will be counted (or detected, if the bacterial population is uncountable) in produce before and after treatment, as well as during storage.
<p>
This study will identify treatment conditions sufficient to eliminate E. coli O157:H7 in fresh produce, at realistic contamination levels, while maintaining product quality and integrity. It will also optimize an ozonation process for scale-up and incorporation into pre-packaging treatments of fresh produce.