Nuclear magnetic resonance imaging of fresh and frozen courgettes

The internal structure of courgette and the effect of freezing the courgette was investigated by nuclear magnetic resonance imaging. The skin, vascular tissue, cortex, seed-bed and seeds were clearly delineated in the fresh vegetable; however, the image of frozen/thawed courgette showed very little contrast between the different tissues. Freezing ruptures the cell walls and alters the tissue morphology; this affects the transverse relaxation of water in the tissue, which in turn changes the image contrast. This report demonstrates that a correct theory to explain the mechanisms that cause proton relaxation in tissues is vital for correlating image contrast with the physicochemical properties of water in plant tissue.