The use of magnetic resonance imaging (MRI) spectroscopy as a real time probe to noninvasively obtain transient moisture profiles during food dehydration is demonstrated. A laboratory-scale wind tunnel drier was constructed. A 2 x 5 x 5 cm3 apple slab was inserted in the probative zone and one-dimensional drying was effected at quasiisothermal conditions. Spatial resolution of 0.60 mm was obtained. The transient moisture profiles were simulated with a simple mass transfer model. Effective diffusivity of water in the apple was calculated as 8.3 x 10(-5) cm2/s.