4. Discussion
Both MRI and NMR were used to investigate tomato fruit ripening in this study and the approaches complemented each
other in the investigation of this complex process. Quantitative MRI was used tomeasuremono-exponential relaxation times. MRI also made it possible to study changes in the fruit macrostructure during ripening such as shrinking of air spaces and development of micro-bubbles in specific tissue types. The non-destructive and non-invasive character of MRI provided the opportunity to follow individual fruit through the ripening process, and this is particularly useful for tomatoes which, like all biological samples, are characterized by wide diversity. In addition, MRI made it possible to avoid disruption of the tissues which, for fruit and vegetable
products, could affect the results. In fact, the following difficulties
were encountered when the samplingwere performed for theNMR
experiments: the core could not be clearly distinguished from the
placenta by visual examination of the fruit and, because of its shape,
it was impossible to extract the radial pericarp using the sampling
method chosen for this study. Finally, results for the placenta may
have been affected by sedimentation. On the other hand, the signal
to noise ratio and the temporal resolution of multi-echo sequences
used for computing T2 and T1 did not permit multi-exponential
fitting, as is the case in the great majority of MRI investigations.
We therefore used non-spatially resolved NMR relaxation measurements
to access the multi-component character of the signal
and to obtain more information about the cell microstructure.