E. Herremans, P. Verboven, B.M. Nicolaï, M. Wevers, P. Estrade, E. Bongaers, B.E. Verlinden
Preservation of quality of apples is a premium target during storage of these fresh products. However, during the production and storage the fruit can develop undesired quality losses, also during CA (controlled atmosphere) storage. ‘Braeburn’ browning disorder (BBD) is such a CA related internal disorder, that cannot be distinguished on the fruit exterior. However, internal disorders are likely to reflect massive changes in the microstructure of the fruit tissue. There is a need for a non-destructive evaluation of internal fruit quality that is fast, reliable and can be used for on-line sorting of disordered fruits. X-rays can detect local density changes and are therefore investigated as a promising tool to detect brown and hollow tissues in apples.
A first objective in this study was to investigate microstructural changes during development of internal flesh browning of ‘Braeburn’ apples. Therefore apple samples were scanned using high resolution X-ray micro computed tomography, at regular intervals after harvest while storing under extreme CA conditions (1% O2, 5% CO2). We gained insight in the microstructure by applying image processing tools to virtually isolate single cells and pores, hereby enabling the detailed 3D characterisation of the in vivo microstructure in terms of the tissue connectivity, the internal air network and the distribution of pores inside the apple tissue in healthy and disordered fruits.
Secondly, we wanted to investigate the feasibility of X-ray tomography to effectively detect these internal disorders at commercial speeds. We scanned a large number of fruits and performed image processing to detect the disorders. In the first trials we could detect affected fruits with a success ratio of 95%, although total scans times were rather high (10 min per fruit) . By significantly lowering the image acquisition time to 38 s, the sorting success was reduced to 82%. Further efforts are needed to speed up the measurements and test the image processing algorithms with newly scanned fruits, however, on-line measurements in a medical CT system have proven the potential applicability of X-ray CT in postharvest sorting facilities.
Herremans, E., Verboven, P., Nicolaï, B.M., Wevers, M., Estrade, P., Bongaers, E. and Verlinden, B.E. (2015). X-RAY VISION TO DETECT CA INDUCED DISORDERS IN 'BRAEBURN' APPLES: FROM MICROSTRUCTURE IMAGING TO ON-LINE SORTING. Acta Hortic. 1071, 129-136
DOI: 10.17660/ActaHortic.2015.1071.12
Malus × domestica Borkh. 'Braeburn', Braeburn browning disorder, microstructure, X-ray CT, on-line sorting

Acta Horticulturae