AN NMR PULSED-FIELD GRADIENT STUDY OF THE ELECTRICAL AND CONVENTIONALHEATING OF CARROT

Experiments have been carried out using pulsed field gradient NMR to c haracterize the selfdiffusion of water within samples of carrot, both uncooked and cooked by either volumetric electrical or conventional he ating. The method detected the presence of structure within uncooked c arrot, and the disappearance of the structure on cooking. The NMR data were fitted to two models: (i) an analytical solution for diffusion b etween impermeable barriers and (ii) a numerical solution to the more physically realistic situation of diffusion between permeable barriers . The barrier spacings obtained with raw carrot data using both method s (i) and (ii) were consistent with cell sizes found in carrots. The e ffect of cooking on the model fit was either an increase in barrier sp acing (method i), or an increase in barrier permeability (method ii). There was a statistically significant difference between samples cooke d electrically and conventionally, but this was much less than the dif ference between cooked and uncooked material.