Li, Yun2012-09-192012-09-192012-07https://hdl.handle.net/11299/133875University of Minnesota Ph.D. dissertation. July 2012. Major: Biosystems and Agricultural Engineering. Advisor: Dr. Roger Ruan. x, 219 pages.Nuclear magnetic resonance techniques, including nuclear magnetic imaging (MRI) and nuclear magnetic resonance (NMR) relaxometry are increasingly gaining interest and acceptance by food scientists and engineers. These techniques are being used to study moisture and fat content, water mobility, and distribution of water, fat, and temperature in foods. They are also used to determine freezing front and viscosity of foods. A unique advantage of NMR techniques is their non-invasive and non-destructive nature, making analysis faster and more reliable than conventional techniques. MRI work in the food area is primarily conducted using expensive and hard to operate large MRI systems. Most food companies, especially small companies, are not willing to use or cannot afford such large systems. Therefore, developing small systems specifically for food samples is an urgent need. NMR relaxometry has been used by food scientists for decades. However, only recently food scientists began to realize that the technique has more to offer. Research on the relationship between NMR relaxation times and physiochemical properties of foods is emerging. A suite of techniques were developed for the acquisition of reliable data and high quality images using low field MRI machines. My research has helped solve some key technical problems by improving the hardware configuration, pulse sequences, and data analysis techniques. In my research, advanced pulse sequences were adapted to our low field MRI machines for MRI imaging work and NMR relaxation work. Pulse sequences were tuned to obtain high quality images. New hardware was developed to accommodate unique samples. New NMR data acquisition schemes and data analysis techniques were developed to obtain additional information for the analysis of food stability. Models were designed for state diagrams. Coding programs were developed to calculate and analyze state diagram related parameters. My work involved both hardware and software improvements to facilitate adaptation and implementation of advanced techniques. It is my hope that these low field MRI machines be improved through my study so that they become an affordable, easy-to-operate, and relatively maintenance free analytical tool for food research and development and quality control labs.en-USMRINMRWater mobilityBiosystems and Agricultural EngineeringThesis or Dissertation