New imaging method to characterize the 3D microstructure of frozen apple tissue using X-ray µCT

Fruit is highly perishable products like other plant based products. Their microstructure is composed of cells of different sizes and shapes, interconnected cell walls and intracellular air space, of again different sizes and shapes. Food microstructure has been recognized as one of the key aspects to define the quality properties for consumers and the food industry. Fruits pose a particular challenge with respect to freezing, in which, ice crystals are formed and distributed over these compartments. In subsequent storage, they are resized and redistributed resulting in microstructural changes. Non-destructive imaging techniques have become indispensable to improve insight in the microstructural changes in fruit during freezing. Here, X-ray µCT was used to visualize and quantify the 3D microstructure and the ice crystal distribution in fruit. In this work, apple cortex tissue was considered as a fruit sample with a microstructure consisting of cells and intercellular spaces of different sizes and shapes. Apple samples excised from the cortex tissues were frozen under three different freezing methods (namely slow, intermediate and fast freezing rates). Afterwards, the microstructure and ice crystals were imaged by µCT coupled with temperature-controlled stage. A developed imaging methodology was validated to segment the frozen phase from the unfrozen matrix. The resulting images were used to compare the ice crystals among the different treatments.status: publishe