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Simulation and Validation of Radio Frequency Heating of Shell Eggs Soon Kiat Lau University of Nebraska-Lincoln, [email protected]

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Simulation and Validation of Radio Frequency Heating of Shell Eggs Soon Kiat Lau University of Nebraska-Lincoln, Lskiat@Huskers.Unl.Edu University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Dissertations, Theses, & Student Research in Food Food Science and Technology Department Science and Technology Summer 7-28-2015 Simulation and Validation of Radio Frequency Heating of Shell Eggs Soon Kiat Lau University of Nebraska-Lincoln, [email protected] Follow this and additional works at: http://digitalcommons.unl.edu/foodscidiss Part of the Food Science Commons, Mechanical Engineering Commons, and the Microbiology Commons Lau, Soon Kiat, "Simulation and Validation of Radio Frequency Heating of Shell Eggs" (2015). Dissertations, Theses, & Student Research in Food Science and Technology. 61. http://digitalcommons.unl.edu/foodscidiss/61 This Article is brought to you for free and open access by the Food Science and Technology Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Dissertations, Theses, & Student Research in Food Science and Technology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. i Simulation and Validation of Radio Frequency Heating of Shell Eggs by Soon Kiat Lau A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science Major: Food Science and Technology Under the Supervision of Professor Jeyamkondan Subbiah Lincoln, Nebraska August, 2015 ii Simulation and Validation of Radio Frequency Heating of Shell Eggs Soon Kiat Lau, M.S. University of Nebraska, 2015 Advisor: Jeyamkondan Subbiah Finite element models were developed with the purpose of finding an optimal radio frequency (RF) heating setup for pasteurizing shell eggs. Material properties of the yolk, albumen, and shell were measured and fitted into equations that were used as inputs for the model. When the egg was heated by itself, heating tend to be focused at the air cell to result in a “coagulation ring.” The focused heating near the air cell of the egg prevented satisfactory pasteurization of the egg, but deeper analysis of the simulation results offered a new perspective on how non-uniform RF heating could occur in heterogeneous food products, especially those that contain air bubbles. By immersing the egg in deionized water, the “coagulation ring” disappeared and heating was concentrated in the yolk after RF heating. Extrapolation of the model suggested that 3 log reductions of Salmonella can be achieved within 37 min of RF heating followed by hot water immersion. In addition, the contamination of the water surrounding the egg was shown to have a positive impact on the heating rate up to a threshold, at which point further contamination decreased the effectiveness of the process. The knowledge gained in this study could be used to design pasteurization equipment for shell eggs that are faster than conventional equipment. iii For the late D.F. and R, the grand magus iv Acknowledgements It goes without saying that a graduate student is nothing without his or her advisor. Dr. Jeyamkondan Subbiah is one of the most prominent figure in my life, and will remain as one whom I will always look up to. I used to be holed up in the world of microbiology and chemistry up until I met Dr. Subbiah who, along with his colleagues, introduced me to a whole new world of food science: engineering and simulations. There is no doubt that at least half of my scientific curiosity was seeded the moment I joined his program as a Master’s student. Dr. Subbiah always provides encouraging advice for me to investigate things that I miss out in my research and perhaps most importantly, life advice that cannot be found anywhere else. Dr. Harshavardhan Thippareddi provided a lot of advice at the beginning of my research, particularly in the area of eggs. Although eggs are so common, I found my knowledge in eggs rather lackluster; Dr. Thippareddi was the one who jumpstarted me in this area. He was also instrumental in the development of the Salmonella thermal death time model used in this research. Dr. Jones gave me some vital advice during the middle of my research and pointed out various areas for improvements. My models would never be the way they are now had I not taken classes under Dr. Florin Bobaru. Considering that a major part of this thesis is about simulations using the finite element model, the teachings of Dr. Bobaru helped propel me into this new research field and even prompted me to apply for a minor under his supervision. v Science is not always about racking one’s brains; it also involves a lot of communication and cooperation. Therefore, my gratitude goes to Dr. Subbiah’s secretary, Amber Patterson who tolerated my many last-minute orders for new equipment and supplies. Without her, my research may have been delayed for months due to lack of supplies! Scott Minchow produces some of the best custom-made equipment with extremely good craftsmanship. The aluminum egg used in the convective heat transfer experiments was possible thanks to information given by Scott. He also helped to build the custom test cells used in property measurements from scratch. This wouldn’t be a project with eggs if there were no eggs to begin with! Therefore, I would like to thank Dr. Sheila Purdum from the Animal Science Department for providing me permission to obtain eggs straight from their department’s coop. Leo Sweet is primarily responsible for helping me with the collection and also provided me with a lot of life advice and useful nuggets of knowledge. Thank you Leo! My labmates, Jiajia Chen, Krishnamoorthy Pitchai and Sreenivasula Boreddy were extremely helpful at the beginning of my project. They helped me when I was still a newbie in experiments in general. They also explained their equipment usage procedures when I was trying to measure the properties of the eggs. The guidance and tips they gave me would have taken me weeks to figure out by myself. Of course, I won’t forget my beloved parents who cared for me since young until I left the nest and without whom, this thesis would have never existed! vi Table of Contents Acknowledgements ...................................................................................................... iv Table of Contents ......................................................................................................... vi List of Tables .................................................................................................................x List of Figures .............................................................................................................. xi Chapter I: Introduction .................................................................................................1 1.1 The Good, The Bad, and the Tiny Killers ..........................................................1 1.2 Radio Frequency Heating .................................................................................3 1.3 Objectives ........................................................................................................5 1.4 Thesis Organization .........................................................................................6 1.5 References ........................................................................................................8 Chapter II: Literature Review .................................................................................... 11 2.1 Radio Frequency Heating ............................................................................... 11 2.2 Theory ............................................................................................................ 12 2.3 Food Applications .......................................................................................... 13 2.4 Nonuniformity ................................................................................................ 14 2.5 Quality of Food .............................................................................................. 14 vii 2.6 Simulations .................................................................................................... 16 2.7. Summary ............................................................................................................. 18 1.6 References ...................................................................................................... 19 Chapter III: Rings in Eggs: Improving Microbiological Safety of Shell Eggs Using Radio Frequency Heating ............................................................................................ 26 Abstract ..................................................................................................................... 26 3.1 Introduction ................................................................................................... 27 3.2 Materials and Methods ................................................................................... 30 3.2.1 Measurement of Properties ......................................................................... 30 3.2.1.1 Preparation of samples ........................................................................ 30 3.2.1.2 Dielectric properties measurement ...................................................... 31 3.2.1.3 Thermal conductivity measurement .................................................... 32 3.2.1.4 Specific heat capacity measurement .................................................... 33 3.2.1.5 Curve fitting ......................................................................................
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