Food Safety Engineering Strategies For Combating Foodborne Bacteria In Food Processing Environments
Food safety engineering is the application of engineering approaches to solve food safety problems. This dissertation showcases two food safety engineering strategies for combating the presence of pathogenic microorganisms in food processing environments and foods. One strategy for eliminating bacterial presence in foods is by using technologies to inactivate microorganisms. Pulsed light (PL) treatment consists of using short duration, high energy bursts of broad spectrum light to inactivate microorganisms. The antimicrobial effectiveness of PL is directly related to the treatment dose (fluence) received by the microorganism. Treatment effectiveness and uniformity can vary greatly depending on the properties of the substrate and the relative location of the pulsed light source. To gain a better understanding of the sources of non-uniform treatment, a numerical model based on mapping the spatial distribution of fluence in conjunction with Weibull inactivation kinetics to predict the volumetric inactivation in PL treatment of liquid substrates with known optical properties and geometry was developed and validated. Information obtained from this work can help processors determine the viability of using PL as a microbicidal treatment without extensive and costly experiments. Another approach for eliminating undesirable bacteria in food processing environments is through preventing bacterial attachment to surfaces. Previous work has suggested that substratum surface topography can influence bacterial attachment. However, no universal trends have been identified. Manipulating surface topography at the nanoscale to control the effective contact area available to the bacterial cells might affect bacterial attachment. The influence of nanoscale surface topography on the attachment behavior of Escherichia coli, Listeria innocua, and Pseudomonas fluorescens to nanoporous alumina and nanoengineered silica substrates was investigated. Bacterial attachment and biofilm formation were observed by wide field fluorescence microscopy, scanning electron microscopy, and atomic force microscopy. The current results suggest that substratum nanoscale topography influences the number of attached cells, and also the relative orientation of cells to the topographical details. Moreover, morphological differences between attached cells indicate that bacteria utilize different mechanisms of attachment in response to nanoscale substratum topography. Insight gained from this type of work will aid in the design of surfaces that resist bacterial attachment and thereby reduce the risk for cross-contamination. Overall, these approaches can work synergistically to positively impact the safety and quality of the food supply.
food safety engineering; pulsed light; nanoscale topography
Moraru, Carmen I
Worobo, Randy W.; Miller, Dennis D.
Food Science and Technology
Ph. D., Food Science and Technology
Doctor of Philosophy
dissertation or thesis