TEMPERATURE MAPPING OF PARTICLES DURING ASEPTIC PROCESSING WITH MAGNETIC-RESONANCE-IMAGING

Magnetic Resonance Imaging (MRI) was used to obtain 2-dimensional temp erature maps in potatoes undergoing aseptic processing. The change in precession frequency of protons served as the temperature indicator. T he larger particles (6.9 and 3.84 cm(3)) showed a Delta T (T-surface - T-center) of up to 22+/-0.4 degrees C 45s after exiting the heat exch anger with the Delta T (T-outlet - T-inlet) of the carrier fluid in th e heat exchanger at 30 to 45 degrees C, No Delta T was measured betwee n the center and the surface of particles <2.05 cm(3) pumped at <22.7 L/min, The average fluid to particle convective heat transfer coeffici ent (h(fp)) for the heat exchanger and holding tube was calculated usi ng a finite element method. The hfp was from 600 to 2500 and >3000 W/m (2) degrees C for the large (6.9 cm(3) cubes) and smaller particles re spectively.