Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Food Product Recalls: Trends and Demand Impacts
    (2016) Tselepidakis, Elina; Lichtenberg, Erik; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Food product recalls, the removal of risky food products from the marketplace, can impose significant burdens for consumers, producers, and regulators. The purpose of this dissertation is to offer an in-depth investigation of the trends and demand impacts of food product recalls. The first objective is to analyze trends and patterns of food product recall events from 2004 to 2013. The analysis considers multiple factors, including the types of foods being recalled, the reasons for initiating the recalls, the severity of the risks posed by the recalled products, and the geographic distribution. The second objective is develop a general Bayesian model to illustrate how consumers form perceptions of risk based on personal experiences and external signals, such as recall events. The model illustrates frequently observed behavior following the release of negative information: an immediate change in behavior, followed by a gradual return to previous, routine behavior. The third objective is to estimate the impact of leafy green recall events on the demand for packaged leafy green products by analyzing disaggregated household purchasing data. The results of this analysis suggests that iceberg and romaine recall events negatively impacted demand for the implicated leafy green in the weeks immediately following the recall. The fourth objective is to estimate the impact of STEC-contaminated ground beef recall events on the demand for ground beef products, differentiating between recalls prompted by consumer illness investigations and those prompted by laboratory testing. The results suggest that the impacts of recalls prompted by consumer illnesses outbreaks were often greater in magnitude and lasted longer than the impacts of recalls prompted by pathogen testing.
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    Investigating Metrics Proposed to Prevent the Harvest of Leafy Green Crops Contaminated by Floodwater
    (2015) Callahan, Mary Theresa; Buchanan, Robert L; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Pathogens can be transported by water through soil to contaminate distant crops. The California LGMA states that leafy green crops within 30ft of flooded soil should be destroyed due to potential contamination. Previously flooded areas should not be replanted for 60 days. This study investigated the transport of Salmonella enterica and Citrobacter freundii through soil in a model system with a positive slope (uphill). Field trials involving flooding one end of a spinach bed with a negative slope (downhill) with water containing Escherichia coli were also conducted. Soil type, soil moisture content, and slope affected bacterial movement. In field trials, E. coli was quickly transported to the 30ft boundary, and persisted significantly longer in the fall trial than the spring. These data suggest the LGMA metrics need to provide additional parameters to prevent the harvest of leafy green crops potentially contaminated by floodwater.