Investigation of Corrosion in Canned Tomatoes Processed by Retorting THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Elliot Dhuey Graduate Program in Food Science and Technology The Ohio State University 2019 Master's Examination Committee: Dr. Melvin Pascall, Advisor Dr. Gerald Frankel Dr. John Litchfield Copyrighted by Elliot Dhuey 2019 Abstract This study investigated the presence of volatile and non-volatile compounds in canned processed tomatoes and how these compounds interacted with the Bisphenol A free epoxy-based lining of the cans to cause corrosion of the base metal and the migration of iron and tin compounds to the tomatoes. The tomatoes tested in this study were the Roma variety. They were sorted, washed, diced, and sealed in two-piece tinplated metal cans. These were processed by retorting at 250°F for 30 minutes then stored at 49°C for up to 50 days. Control samples were packaged and processed in glass jars. The presence and concentrations of the volatile and non-volatile compounds in the processed and unprocessed tomatoes were tested using Selected Ion Flow Tube – Mass Spectrometry (SIFT-MS) and Ion Chromatography – Mass Spectrometry (IC-MS) respectively. After removing the processed tomatoes from the cans, the linings were removed and analyzed for the volatile and non-volatiles as was mentioned before. Scanning Electron Microscopy (SEM) paired with Energy Dispersive X-ray Spectroscopy (EDS) was used to confirm the presence of visual corrosion in the processed cans and to analyze its elemental composition. X-ray Diffraction (XRD) and Fourier Transform – Near Infrared (FT-NIR) was used to characterize changes to the polymeric morphology of the can lining after the retort processing. Also, Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) was used to determine the rate and level of tin and iron migration from the metal can to the tomato product. The results of the SIFT analyses showed that ii the formation of dimethyl sulfide and other sulfide compounds in the tomatoes resulted from the thermal degradation of methyl methionine. These compounds diffused from the tomatoes to the lining of the cans and the XRD and FT-NIR analyses showed that they interacted with the polymer and led to the reformation of the oxirane ring of the epoxy and binding of water with the polymer lining. The SEM analysis showed that sulfur compounds created breaches in the lining and created avenues for corrosive compounds in the tomatoes to interact with the base metal layer. The presence of nitrates resulted in an increased rate of iron migration when combined with sulfur compounds. From the results obtained, it could be concluded that the combination of volatile and non-volatile compounds found in tomatoes are acting synergistically to initiate corrosion in the tin and steel in the walls of the cans used to package the retorted tomatoes. iii Dedication Dedicated to my loving parents, Charles and Michele Dhuey, who raised me to believe that with God all things are possible. iv Acknowledgments I would like to sincerely thank my advisor Dr. Melvin Pascall for his incredible support, guidance, and knowledge to help me complete my master’s thesis at The Ohio State University. The past two years have been incredible to witness the level of effort and detail that Dr. Pascall puts into his students’ research and making sure his students learn and grow is remarkable and inspiring. I would also like to thank Dr. Gerald Frankel and Dr. Christopher Hadad for their support and knowledge in areas around my research to help make it successful. The support I received from the Dr. Jaesung Lee, Dr. Hardy Castada, and Dr. Jojo Joseph, and Ryan Hopf have also made this all possible. Kuo-Hsiang Chang’s help with SEM-EDS and processing tomatoes was much needed and appreciated. Additionally, I want to thank Ken Ruffley at PPG for his guidance and being our champion through this project. The combined financial support from PPG and USDA-NIFA have helped make this project successful. Lastly, I would like to thank my amazing friends who were able to help me with anything I needed during my masters. Whether it was processing pounds of tomatoes in the food processing plant that was set up by Matt Papic or being there to make my experience at OSU amazing, I’m grateful either way. v Vita 2012................................................................Sun Prairie High School 2017................................................................B.S. Food Science & Technology, University of Wisconsin – Madison 2017 to Present ...............................................Master’s Student, Food Science & Technology, The Ohio State University Fields of Study Major Field: Food Science and Technology vi Table of Contents Abstract …………………………………………………………………………………...ii Dedication ………………………………………………………………………………..iv Acknowledgements ……………………………………………………………………….v Vita ……………………………………………………………………………………….vi List of Tables …………………………………………………………………………….xi List of Figures ………………………………………………………………………..…xii Chapter 1: Introduction ................................................................................................... 1 Chapter 2: Literature Review.......................................................................................... 5 2.1 Packaging of food................................................................................................. 5 2.1.1 Types of packaging materials ........................................................................... 6 2.1.2 Cans .................................................................................................................. 7 2.1.2.1 Three-piece cans ........................................................................................... 8 2.1.2.2 Two-piece cans ........................................................................................... 11 2.1.2.3 Can coating ................................................................................................. 12 2.2 Enamel Coating .................................................................................................. 15 2.2.1 Common types of enamel resins ..................................................................... 16 2.2.2 Bisphenol A controversy ................................................................................ 17 vii 2.3 Tomatoes ............................................................................................................ 19 2.3.1 Compounds in tomatoes ................................................................................. 19 2.3.1.1 Nitrogenous compounds ............................................................................. 22 2.3.1.2 Sulfur compounds ....................................................................................... 25 2.3.2 Processing of tomatoes ................................................................................... 27 2.4 Canned food products......................................................................................... 29 2.4.1 Canning process .............................................................................................. 30 2.4.1.1 Filling .......................................................................................................... 30 2.4.1.2 Pressure and headspace ............................................................................... 30 2.4.1.3 Can seaming ................................................................................................ 31 2.4.1.4 Retorting ..................................................................................................... 34 2.4.1.5 Heat penetration .......................................................................................... 36 2.5 Corrosion in canned food ................................................................................... 40 2.5.1 Mechanisms of corrosion................................................................................ 40 2.5.2 Factors influencing corrosion in canned food and beverage .......................... 43 2.6 Methods of corrosion detection .......................................................................... 46 2.6.1 Corrosion inspection technology .................................................................... 46 2.6.1.1 Visual inspection ......................................................................................... 46 2.6.1.2 Ultrasonic inspection .................................................................................. 47 viii 2.6.1.3 Radiographic inspection.............................................................................. 48 2.6.2 Scanning Electron Microscopy – X-Ray Microanalysis ................................ 49 2.6.3 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) .......................... 51 2.7 Select Ion Flow Tube Mass Spectrometry (SIFT-MS) ...................................... 52 2.8 Ion Chromatography .......................................................................................... 54 2.9 Attenuated Total Reflectance (ATR) ................................................................. 56 2.10 Dynamic Mechanical Analysis (DMA).............................................................. 57 2.11 Permeability ....................................................................................................... 58 Chapter 3: Materials and Methods ...............................................................................