Characterisation of 'Braeburn' browning disorder by means of X-ray micro-CT

Unfavourable gas conditions during controlled atmosphere storage may cause browning symptoms in 'Braeburn' apple fruit ('Braeburn' browning disorder or BBD). These symptoms are likely to reflect massive changes in the microstructure of the fruit tissue. In this study, individual cells, the internal air network and the 3-D distribution of pores inside 'Braeburn' apple tissue were examined using high resolution X-ray micro computed tomography. Different stages of BBD could be clearly resolved on the virtual cross-sections, granting a unique 3-D insight in tissue flooding and formation of cavities in 'Braeburn' tissue during the development of the disorder. Image analysis methods were applied to extract morphometric parameters such as porosity, anisotropy and connectivity to characterise microstructure. The discriminative power of these descriptors was proven by their ability to classify fruit tissue as healthy and disordered with a success rate of 97%. The observed distinct radial patterns of porosity, anisotropy and connectivity may help in explaining why 'Braeburn' is susceptible to BBD.