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Analysis of the 3D microstructure of pomegranate peel tissue using X-ray micro-CT

Ambaw, A., Arendse, E., Du Plessis, A., Opara, U. L.
Acta horticulturae 2018 no.1201 pp. 197-204
microstructure, intercellular spaces, cultivars, mathematical models, fruits, pomegranates, micro-computed tomography, porosity, permeability, X-radiation, South Africa
The size and distribution of pores in the peel of pomegranate fruit has an important influence on the moisture and gas transport phenomena that occur in the fruit tissue during storage. However, its detailed structure is still unclear. In this work, the first reported results of laboratory-based X-ray micro tomographic studies of the pomegranate fruit peel is presented. The study was conducted on 'Wonderful', the most important pomegranate cultivar produced and exported from the Western Cape, South Africa. After image acquisition, two-dimensional (2D) images were reconstructed into three-dimensional (3D) volumes. Preliminary sensitivity analyses were performed to investigate the effect of the resolution, which gives a spatial resolution of 3.0 μm as sufficient. The void fraction, absolute permeability and hydraulic tortuosity were calculated for peel sample taken from the top, middle and bottom region of the fruit. In the top part of the fruit, around the calix, the porosity of the peel tissue was consistently lower. The 3D imaging of the intercellular spaces revealed that these spaces were not completely interconnected and were disrupted in some parts. The viscous transport of water through the 3D microstructure was also modelled using a direct voxel-based 2-phase material model. The result of this study will further be used for numerical modeling of transport processes in pomegranate fruit.