Doctor of Philosophy, The Ohio State University, 2015, Comparative and Veterinary Medicine

Human norovirus (NoV) is responsible for more than 95% of nonbacterial gastroenteritis and over 60% of foodborne illness each year in the US. However, it has been a challenge to conduct research on human NoV because it cannot be grown in cell culture and lacks a small animal model. Despite major efforts, there is no antiviral therapeutic or vaccine for human NoV. In addition, the survival of human NoV is poorly understood. Fresh produce is major high risk food for human NoV-related outbreaks of gastroenteritis because it can easily become contaminated at any point during pre-harvest and post-harvest stages of production. However the ecology, persistence, and interaction of human NoV in produce systems is poorly understood. Determining the mechanisms underlying human NoV fresh produce contamination can facilitate the development of effective preventative and control measures to limit human NoV outbreaks. The objectives of this research are to determine whether human NoV and its surrogates become internalized via the root of growing produce and disseminated to the edible portion of the plants grown in soil; to determine whether biotic and abiotic stress can affect the rate of internalization and dissemination of human NoV in fresh produce; and to determine whether non-thermal food processing technologies can effectively inactivate internalized viruses while maintaining the fresh quality of produce. Romaine lettuce grown in soil was inoculated with 2 × 108 plaque forming unit (PFU) of human NoV surrogates [Murine norovirus-1 (MNV-1); Tulane virus (TV)] via the roots of plants. Plants were grown for 14 days and leaves, shoots, and roots of each plant were harvested and homogenized and viral titer was determined by plaque assay. It was found that both MNV-1 and TV can efficiently be internalized via plant roots and disseminated to shoots and leaves of lettuce. At day 14 post-inoculation, the titer of MNV-1 and TV in leaves of lettuce plants reached a level of (open full item for complete abstract)

Committee: Jianrong Li PhD (Advisor); Melvin Pascall PhD (Committee Member); Mark Peeples PhD (Committee Member); Wondwossen Gebreyes (Committee Member) Subjects: Food Science; Virology

Doctor of Philosophy, The Ohio State University, 2012, Food Science and Technology

Human norovirus remains the most prevalent foodborne pathogen, resulting in 58% of all foodborne illnesses in the United States, annually. Due to lack of successful cultivation techniques for this virus, research on intervention strategies and disinfection practices to combat this pathogen is still largely underreported. The research performed in this dissertation determined the efficacy of electron beam (e-beam) irradiation and sodium hypochlorite sanitizers at inactivating a human norovirus surrogate (murine norovirus 1, MNV-1) and compared the rates of inactivation against that of an enveloped virus (vesicular stomatitis virus, VSV). This research also attempted to determine the mechanism of viral inactivation for e-beam and sodium hypochlorite. In Chapter 2, we evaluated the efficacy of e-beam at inactivating MNV-1 inoculated to liquid model systems (phosphate buffered saline, PBS; Dulbecco's Modified Eagle Medium, DMEM) and fresh produce (shredded cabbage, cut strawberries). MNV-1 proved to be resistant to irradiation in both liquid and food samples. In PBS and DMEM, a dose of 2 kGy provided a less than 1 log reduction of MNV-1. At doses of 4, 6, 8, 10, and 12 kGy, viral reduction in PBS ranged from 2.37 to 6.40 logs, and 1.40 to 3.59 logs in DMEM. At 4 kGy (the maximum irradiation dose approved by the FDA for fresh produce), MNV-1 inoculated to shredded cabbage only experienced a 1 log reduction, and less than 1 log reduction in cut strawberries. Even at 12 kGy, MNV-1 titers were reduced by 3 and 2 logs in cabbage and strawberries, respectively. These results suggest that complex liquid media and the food matrix may protect MNV-1 from irradiation, and that viruses tend to be more resistant to irradiation than bacteria due to their small size and highly stable viral capsid. E-beam does not appear to be a feasible processing technology to inactivate foodborne viruses in food products. Chapter 3 compares e-beam's ability to inactivate the nonenveloped MNV-1 vers (open full item for complete abstract)

Committee: Ken Lee PhD (Advisor); Jianrong Li PhD (Committee Member); V.M. Balasubramaniam PhD (Committee Member); Jiyoung Lee PhD (Committee Member) Subjects: Food Science

Doctor of Philosophy, The Ohio State University, 2012, Food Science and Technology

Food contact surfaces may present a potential health hazard if they are not properly cleaned and sanitized. Contaminated surfaces (e.g. utensils, cutting boards, equipment) have been identified as sources of cross-contamination for food during preparation and when being served to consumers. Therefore, ensuring effective cleaning and sanitization of food contact surfaces may help in the spread of foodborne pathogens and incidence of outbreaks. The FDA Food Code and NSF International standards mandate that all surfaces/tableware items should be free of food soils and that a minimum microbial reduction of 5 logs must be obtained before surface sanitization could be considered effective. To comply with these standards, food service establishments must clean and sanitize food contact surfaces either manually or mechanically. Unfortunately, the standards set for these ware-washing methods specifically address the reduction of bacterial numbers from food contact surfaces, and not viruses. Therefore, information regarding the effectiveness of these standards against viruses needs to be elucidated. The first part of this dissertation (Chapter 2) compared the efficacy of sodium hypochlorite (chlorine) and quaternary ammonium compound (QAC) in reducing bacterial populations (Escherichia coli K-12 and Listeria innocua) and murine norovirus (MNV-1) counts on different food contact surfaces (ceramic plates, stainless steel forks and drinking glasses). Each microorganism was separately inoculated into 2% reduced fat UHT milk and creamcheese spread. The milk was used to contaminate the drinking glasses and the spreadable cream cheese was used on the ceramic plates and forks. All tableware items were manually and mechanically washed and sanitized. Bacterial and viral counts were then determined on the surface of each tableware item using the plaque assay and plate count methods, respectively. This study found that QAC and sodium hypochlorite sanitizers had the ability to produce gre (open full item for complete abstract)

Committee: Melvin Pascall PhD (Advisor); Jianrong Li PhD (Committee Member); Hua Wang PhD (Committee Member); Gerald Frankel PhD (Committee Member) Subjects: Food Science; Public Health

Doctor of Philosophy, The Ohio State University, 2013, Food Science and Technology

Edible films and coatings are increasingly being used as carriers of functional additives including antimicrobial agents. Consumer interest in naturally-derived antimicrobials has also increased. Plant extracts such as grape seed and green tea extracts are known to have antiviral as well as antibacterial activities. Even though there are several researches that have investigated the use of edible films and coatings as carriers of antimicrobial agents against foodborne bacterial pathogens, unfortunately data is lacking on the use of these same technologies on foodborne viruses. Therefore, this study seeks to develop edible films and coatings that can control foodborne viruses. The film's antibacterial and mechanical properties were also tested. Chapters 1 and 2 introduce and review previous researches in edible films and coatings. Topics such as the types of biopolymer, film formation methods and mechanisms, foodborne viruses and bacteria, as well as edible film characterization and properties are discussed. Chapter 3 of this study investigated the virucidal activity of green tea extract (GTE) dissolved in deionized water and also incorporated into chitosan film forming solutions (FFS) and into chitosan films. For comparison, the antibacterial activity of the films was also investigated against Listeria innocua and Escherichia coli K12. The viral infectivity after treatments was measured by plaque assays. The 1, 1.5 and 2.5% aqueous GTE solutions significantly (p<0.05) reduced murine norovirus (MNV-1) plaques by 1.69, 2.47, and 3.26 log after 3 h exposure, respectively. Similarly, the FFS containing 2.5 and 5.0% GTE reduced MNV-1 counts by 2.45 and 3.97 log10 PFU/ml, respectively after 3 h exposure. Additionally, the edible films enriched with the GTE (5, 10 and 15%) were also effective against MNV-1. After a 24 h incubation period, the 5 and 10% GTE films significantly (p<0.05) resulted in MNV-1 titer reductions of 1.60 and 4.50 log10 PFU/ml, respectively. The (open full item for complete abstract)

Committee: Melvin Pascall PhD (Advisor); Jianrong Li PhD (Committee Member); Jiyoung Lee PhD (Committee Member); John Litchfield PhD (Committee Member) Subjects: Food Science