Changes in apple tissue with storage time: Rheological, textural and microstructural analyses

In this study, two varieties of apples with different textural characteristics—“Granny Smith” and “Golden Delicious”—were chosen to evaluate the efficacy of rheological and textural analyses. Dynamic rheological measurements (using a controlled stress rheometer), large deformation texture analysis (uniaxial compression and penetration, using a TAXTplus) and cryo-scanning electron microscopy were used to study the macro- and microscopic changes in apple tissue structure during 14 days of storage at 20 °C. The results obtained showed that both dynamic small deformation and static large deformation tests may be used to monitor mechanical changes in apple tissues. Observation of apple flesh microstructure revealed many changes that could be related to macroscopic changes in texture and rheology. All samples with low storage modulus and Young’s modulus values had microstructural characteristics with some component of the textural unity (middle lamella, cell wall or cell membrane) affected, resulting in effects such as exudation, loss of cell material and cell separation.