Magnetic resonance imaging and relaxometry to visualize internal freeze damage to pickling cucumber

Magnetic resonance (MR) images and tissue relaxometry (T-1 and T-2) data, using a 9.4T MR system, were used to assess freeze damage to pickling cucumbers. Freeze damage was induced by placing cucumbers at -18 degrees C for 150 min and the samples were then stored in a controlled atmosphere. T-1 and T-2-weighted images were generated at echo time (TE) of 10 ms at specific intervals for cucumbers stored for a period of 7 d. Texture profile analysis of the control and freeze-damaged samples was also carried out on the day of MR imaging. MR images showed good contrast between different physiological constituents of a pickling cucumber. A subsurface region in the freeze damaged samples was distinctly different in all MR images which could be physically correlated with damaged tissues visible in a cut-away section of the freeze-damaged pickling cucumber. Spin-lattice relaxation time (T-1) was not different for different constituents of a pickling cucumber and could not be used to resolve between control and freeze damaged samples. Whereas, spin-spin relaxation time (T-2) values for all the regions of a cucumber slice were higher for the freeze-damaged samples than that for control samples. The T-2 values for seeds and the gel around seeds sections were also significantly different from the rest of the cucumber constituents. However, T-2 values did not change significantly over the storage period. Firmness and chewiness characteristics of pickling cucumbers changed during the storage; however, there was no correlation seen between T-2 values and firmness of the fruit. (C) 2012 Elsevier B.V. All rights reserved.