Quantification of microporosity in fruit by MRI at various magnetic fields: comparison with X-ray microtomography.

Microstructure determines the mechanical and transport properties of fruit tissues. One important characteristic of the microstructure is the relative volume fraction of gas-filled intercellular spaces, i.e., the tissue microporosity. Quantification of this microporosity is fundamental for investigating the relationship between gas transfer and various disorders in fruit. We present a new method for quantifying the apparent microporosity using magnetic resonance imaging (MRI). The method is based on the differences in magnetic susceptibility between gas-filled intercellular spaces and their environment inside fruit tissues. It was tested at two different magnetic fields (1.5 and 0.2 T) on apple and tomato fruit. The method was validated by comparing the MRI results with estimation of local tissue porosity using X-ray microtomography experiments. MRI was shown to be effective in determining the distribution of apparent microporosity in fruit.