MONITORING THE FORMATION OF ICE DURING FOOD FREEZING BY MAGNETIC-RESONANCE-IMAGING

The formation of ice during food freezing was examined by magnetic res onance imaging (MRI). Formation of ice was seen as a reduction in spat ially located NMR signal intensity. Potatoes, carrots, peas, corn, and chicken legs were studied with an image resolution of 350 mu m. Inter nal structures differentiated by water or fat content were highlighted by MRI. For all but corn, the ice interface advanced uniformly but as ymmetrically Corn kernels froze individually in a process possibly gov erned by ice nucleation The time required for the signal to disappear corresponded to that required to reach steady-state enthalpy. MRI coul d serve to assess freezing times and the importance of food structure to the freezing process.