Temperature Mapping of Particles During Aseptic Processing with Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) was used to obtain 2‐dimensional temperature maps in potatoes undergoing aseptic processing. The change in precession frequency of protons served as the temperature indicator. The larger particles (6.9 and 3.84 cm3) showed a δT (T surface ‐ T center ) of up to 22±0.4°C 45s after exiting the heat exchanger with the δ (T outlet ‐ T inlet ) of the carrier fluid in the heat exchanger at 30 to 45°C. No AT was measured between 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 coefficient (h fp ) for the heat exchanger and holding tube was calculated using a finite element method. The hfp was from 600 to 2500 and >3000 W/m 2 °C for the large (6.9 cm 3 cubes) and smaller particles respectively.