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A fast low angle shoot (FLASH) pulse sequence in combination with a multiinversion procedure was used to rapidly acquire spin-lattice relaxation data for food particles undergoing ohmic heating. The relaxation data acquired by magnetic resonance imaging (MRI) were analyzed using a two-component exponential model to extract both short and long spin-lattice relaxation time, T 1 . The longer T 1 showed a better linear relationship with temperature than the shorter T 1 and, therefore, was used to produce more reliable temperature maps. The MRI temperature maps constructed for ohmically heated food particulates showed an entirely different heating pattern than would be found for similar but conventionally heated particulates and indicated that the temperature inside the particulate could be higher than near the surface of the particulate.Key Words: MRI, ohmic heating, temperature mapping methods provide information useful for process verification but are invasive. In addition, their results were obtained by post-processing analyses from limited regions within the collected particulates. Magnetic resonance imaging (MRI) can in principle provide effective, noninvasive temperature mapping for use in food science and technology (Schrader et al., 1992;Hill, 1995). However, there are problems with the use of MRI mapping techniques for monitoring temperature distribution in foods that are undergoing processing. Problems with long data acquisition time and effect of heating-induced structural changes on MRI parameters need to be better understood and overcome. Consequently, it is important to develop techniques that have the capability of fast tracking the changes in temperature that occur during a rapid heating process. It is also important to understand which MRI parameters best reflect thermal conditions of the materials and can be extracted from other MRI information. The objective of this study was to develop a fast and reliable MRI technique for mapping temperatures in ohmically heated particulate foods.

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