Non destructive analysis of the wax layer of apple (Malus domestica Borkh.) by means of confocal laser scanning microscopy

Confocal laser scanning microscopy (CLSM) was used to non-destructively ana lyse the changes in the structure and thickness of the cuticle during stora ge of apples (Malus domestica Borkh.). Interpretation of the confocal image s was performed by comparison with scanning electron microscopy and environ mental scanning electron microscopy images. The natural reflectance of the wax and the auto-fluorescence of the underlying cells made it possible with CLSM to distinguish the wax from the underlying layers without any pretrea tment of the fruit. The thickness of the consecutive layers (wax, cutin, ce lls) could be estimated from measurements of the reflection and fluorescenc e intensities as a function of the number of pixels. The mean wax-layer thi ckness measured in this way amounted to 2.58 mum, 3.41 mum or 4.14 mum for the cultivars Jonagold, Jonagored and Elstar, respectively. Changes in the wax structure and cells of the same important Belgian apple cultivars as me ntioned above were monitored during nine months of storage in ultra low oxy gen and after exposure to ambient conditions. The changes in the wax ultras tructure and cell morphology are likely related to water losses and specifi c protection of the apple cultivars against water losses during storage and shelf life.