The 'Fuji' apple cultivar is important economically and is one of South Africa's most cultivated apple cultivars. Internal browning of these apples during storage is therefore not wished for.
A study by several researchers analysed affected and unaffected tissue of 'Fuji' apples after 3 days' exposure to a storage atmosphere with 0.1 % O2 and 50 % CO2. X-ray CT scanning was able to give pore and cell microstructural information such as porosity, length, sphericity, connectivity, equivalent diameter, and anisotropy. 3D image analysis showed that brown affected fruit tissue had signiﬁcantly lower porosity and lower pore connectivity, due to ﬁlling of pore spaces with cellular ﬂuids released after cell damage caused by the high CO2/low O2 stress.
Internal browning was concentrated in the core of the fruit and developed in 31 % of the analysed fruit at different degrees of severity.
The study provided in-depth insight into the effects of short-term high CO2/low O2 stress conditions on the microstructural properties of South African grown 'Fuji' apples. It also showed that tissue microstructure inﬂuences the susceptibility of different regions within the same fruit to stress-induced IB symptoms.
Prof Anton du Plessis