Estimation of the density of pomegranate fruit and their fractions using X-ray computed tomography calibrated with polymeric materials

The application of microfocus X-ray computed tomography (μCT) with a density calibration with homogenous polymeric materials ranging from 910 to 2150 kg m^-3 and its accuracy for differentiating fruit fractions (albedo and arils) and the effects of detecting false codling moth and blackheart disease in pomegranate fruit was investigated. A commercial microfocus X-ray (μCT) system in combination with image analysis techniques was used to generate two-dimensional (2-D) radioscopic images which were reconstructed into three dimensional (3-D) images. Optimum μCT settings were obtained using an isotropic voxel size of 71.4 μm based on a radiation source generated from a voltage of 100 kV with the electric current set at 200 μA. The density of whole pomegranate fruit, its fractions (arils and albedo), false codling moth, and blackheart infected portions were successfully determined within the calibration range. Furthermore, the density of larva moth (9400 ± 40 kg m^-3) were found to be significantly (p < 0.0001) lower than whole fruit (1070 ± 20 kg m^-3) and fruit fractions (arils 1120 ± 40 kg m^-3 and albedo 1040 ± 30 kg m^-3). Similarly, the differentiation between healthy and blackheart affected fruit was successfully accomplished. The density of healthy fruit was significantly (p < 0.0001) higher (1070 ± 20 kg m^-3) than that of fruit affected by blackheart which ranged from 870 to 1000 kg m^-3. The results thus demonstrated that X-ray μCT with associated algorithm can be used to accurately detect and quantify internal defects caused by false codling moth and blackheart disease in pomegranate fruit.