Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Kristen Gibson

Committee Member

Ruben Morawicki

Second Committee Member

Young Min Kwon

Keywords

Food Safety, Ozone, Produce

Abstract

Produce is susceptible to contamination by foodborne pathogens. Food service establishments utilize sanitizing agents to reduce microbes on produce surfaces. The research objectives were to evaluate the efficacy of aqueous ozone 1) on the inactivation of viruses and bacteria on produce; 2) on the inactivation of viruses on stainless steel; and 3) against viruses in association with bacteria on produce surfaces. For objective 1, Boston bibb lettuce and cherry tomatoes were spot inoculated with a cocktail of viruses (murine norovirus (MNV) and MS2 bacteriophage) or bacteria (Enterobacter cloacae and Bacillus cereus) and washed for 40 min with samples taken every 10 min. For objective 2, stainless steel (SS) coupons were spot inoculated with the same cocktail of viruses and washed for 0.5, 3, and 10 min. For objective 3, Boston bibb was spot inoculated with either MNV and E. cloacae or MNV and B. cereus and washed for 40 min with samples taken every 10 min. Inocula were allowed to dry for > 90 min. A batch wash ozone sanitation system (BWOSS) was prepared with ice (3-5°C) and 0.5 ppm ozone or no ozone. Surfaces were treated with either an ozone or water wash with samples taken over time and repeated in at least duplicate. Samples were processed to determine plaque forming units (PFU) and colony forming units (CFU). In objective 1, there were no significant differences in inactivation of MNV, MS2, or bacteria with ozone compared to water only. There was greater variability in viral reduction while bacterial inactivation increased over time. In objective 2, there was no significant difference in inactivation of MNV or MS2 on SS, but the variability was reduced. The log reduction difference between ozone and water for MNV and MS2 after 10 min was 0.25 and 0.51 PFU/ml, respectively. In objective 3, MNV-bacteria association on lettuce did not impact ozone inactivation of MNV. The log reduction differences between ozone and water for MNV with B. cereus and MNV with E. cloacae after 40 min were 0.95 and -0.36 PFU/ml, respectively. Further research is needed on how food matrices effects viral inactivation by ozone.

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