'Fuji' apple internal browning explored via X-ray computed tomography (CT)
Internal browning (IB) of 'Fuji' apples (Malus × domestica Borkh.) is an important physiological disorder which occurs during long term controlled atmosphere and regular atmosphere storage. The aim of this study was to use micro- and nano X-ray computed tomography (CT) to establish differences in airspace shape and size (tissue density) and porosity of the fruit with and without IB. The fruit was subjected to 50% CO2 at ambient temperature for three days after harvest, and afterwards evaluated for IB. Micro- and nano X-ray CT scans were performed on 20 affected and unaffected fruit using the General Electric Phoenix V │Tome│ X L240 (240 kV) at Stellenbosch University. Preliminary results show that the high CO2 concentration had a significant effect on browning incidence in 'Fuji' apples. CO2 induced browning was concentrated around the centre of the fruit and became less pronounced towards the periphery of the fruit. The CT scans also showed that IB did not have a significant effect on the tissue density. Affected tissues had a higher tissue density although it was not significantly higher than the density in unaffected tissues. The affected tissues had lower porosity compared to non-affected tissues. The lower porosity in affected tissues and microstructural organisation is postulated to inhibit the supply of oxygen to these tissues leading to fermentation and eventual cellular collapse, which may in turn be responsible for IB.
Chigwaya, K., Schoeman, L., Fourie, W.J., Crouch, I., Viljoen, D. and Crouch, E.M. (2018). 'Fuji' apple internal browning explored via X-ray computed tomography (CT). Acta Hortic. 1201, 309-316
Malus × domestica, porosity, tissue connectivity, CO2 induced internal browning