Monitoring volatile organic compound (VOC) release in relation to microstructure and texture characteristics in apples.
Apples are climacteric fruits that continue to ripen after harvest. During prolonged storage, ripening leads to an increase of VOCs and the slow dissolution of cell walls. Here, juice that was once held within a cellular matrix permeates through the cells. In some cases, apples can “dry out” due to an excessive loss of moisture. Cell wall breakdown and moisture loss (flaccid tissue) can result in the increased formation of intercellular spaces and the undesirable mealy, floury or grainy texture experienced by consumers when eating soft apples. To investigate the relationship between the morphological properties (porosity, intercellular space size) in an apple microstructure and texture, a visual microscopy technique known as the X-ray microcomputer tomographic, µ-CT scanner was used. Images from the µ-CT scanner generate 3-D structures showing the apple microstructures. In general, results showed firm apples contained a low porosity and a higher dry matter (%), while the opposite was true for soft apples. However, this trend was not visible for all cultivars. Specific differences from the microstructural organization appear to influence the mechanical strength of the parenchyma tissue. This in turn, impacts perceived firmness. For example, a firm Fuji apple may be similar in porosity compared to a softer Golden Delicious. When the µ-CT images were visualized, Fuji apples appeared to contain a lot of smaller and more compact intercellular spaces, compared to Golden Delicious which contained larger interconnected intercellular spaces. It is hoped that these findings will contribute to understanding eating quality in apples.