Application of magnetic resonance imaging to pre- and post-harvest studies of fruits and vegetables

As magnetic resonance imaging (MRI) systems with cryomagnets large enough to accommodate samples of interest to postharvest researchers become more accessible, MRI will come to be regarded as an integral component in pre- and post-harvest investigations of physiological changes in fruit and vegetables. The non-invasive, non-destructive attributes of H-1 MRI, and its ability to provide highly resolved spatial information concerning the distribution and magnetic environment of water in soft tissues, makes it an attractive technique for probing such samples. In reports to date, examination of the quality, histology, histochemistry and structural characteristics of samples have been emphasised. These and other applications pertaining to the study of fruits and vegetables are reviewed, as well as recent developments that employ nuclear magnetic resonance principles as on-line sensors in postharvest sorting and processing situations. (C) 1997 Elsevier Science B.V

H-1-Nuclear magnetic resonance imaging of ripening 'Kensington Pride' mango fruit

Physicochemical gradients occur in mango mesocarp tissue during ripening. These gradients are reflected in water activity, which is non-uniform throughout the mesocarp. Signal intensity in proton magnetic resonance images (first echo, proton density and T-2) for green-mature 'Kensington Pride' mesocarp tissue was highest near the endocarp and lowest near the exocarp. Relative signal intensity increased in the middle mesocarp as ripening proceeded, but remained relatively low in the outer mesocarp. T-2 relaxation times for inner and middle mesocarp regions fell during ripening. The data suggest that water activity in the mesocarp tissue increased in an outward-moving flux as ripening progressed. This change in water activity was associated with starch hydrolysis and other ripening-related processes that commence near the endocarp