The physical and chemical changes that occur in foods during growth, harvest, processing, storage, preparation, and consumption are often very difficult to measure and quantify. Magnetic resonance imaging (MRI) is a pioneering technology, originally developed in the medical field, that is now being used in a large number of disciplines to study a wide variety of materials and processes. In food science, MRI techniques allow the interior of foods to be imaged noninvasively and nondestructively. These images can then be quantified to yield information about several processes and material properties, such as mass and heat transfer, fat and ice crystallization, gelation, water mobidity, composition and volume changes, food stability and maturation, flow behavior, and temperature. This article introduces the fundamental principles of MRI, presents some of the recent advances in MRI technology, and reviews some of the current applications of MRI in food science research.
Two dimensional temperature maps of a model food gel (agar, microcrystalline cellulose, and water, 1.95:6.55:200), were obtained by MRI during heating and cooling. The molecular pseudo self-diffusion coefficient of water was used as a temperature indicator. A two dimensional Fourier transform spin-echo imaging sequence was used for data acquisition. The self-diffusion coefficient at room temperature was 1.26 x 1O-3 mm2/sec. Two dimensional self-diffusion images were obtained, and temperature images were calculated. The error in MRI measurements, due to noise and temperature variation, was less than 1°C with 1.5 mm2 resolution. The average variation between MRI and thermocouple measurements was < 1.26"C. This new noninvasive technique can be used to study heat transfer and to measure thermal properties of foods.
Two dimensional temperature maps of a potato during heating were obtained using magnetic resonance imaging (MRI) techniques. the molecular pseudo self‐diffusion coefficient of the water in the potato was used as a temperature indicator. Two dimensional half Fourier transform spin‐echo and Generalized Series reconstruction techniques were used to reduce data acquisition time to about 10 s/image and to improve temperature mapping resolution. Thermocouples were implanted into the sample so that temperature and MRI data were acquired simultaneously. the error in MRI measurements caused by noise and the time delay required to collect each data set was less than 0.84C with 0.75 mm2 resolution. the average variation between MRI and thermocouple measurements was less than 0.5C. This is a promising new technique to noninvasively study heat transfer and to measure thermal properties of food materials.
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