Pomegranate fruit easily loses moisture although it has a thick rind and tough leathery outer skin. This results in compromised visual appearance and ﬁnancial loss, and in extreme cases, postharvest loss of affected fruit. A study was done by a team from SARChI Postharvest Technology at Stellenbosch University to identify and characterise structural changes in lenticels, micro-cracks, wax patterns and peel tissue fractions to understand the water loss trends in pomegranate fruit during storage.
Scanning Electron Microscopy (SEM) at the CAF SEM Unit was used for micro-examination of surface structures. Confocal laser scanning was performed at the CAF Fluorescence Microscopy (FM) Unit for micro-examination of the waxy cuticle.
Several structural features like surface openings and wax patterns were identified on the pomegranate peel surface. The peel thickness is lower at the calyx-end of the fruit. There is also a higher count of lenticels, larger lenticel size, greater porosity, circularity and roundness of lenticels at the calyx-end of the fruit. This makes the calyx-end more vulnerable to water loss compared to the equatorial and stem-end regions.
The study suggests a water loss control technique that considers the variation of surface openings of the different regions. Surface waxing and coating can be optimised through strategically differentiated treatment of the fruit surface. Compromised fruit appearances can also be minimised.
M Frazenburg (CAF SEM Unit)
UL Opara (author)