Postharvest moisture loss studies in Japanese plums (Prunus salicina Lindl.)

A comparison of cuticle ultrastructure, chemical composition, peel permeability and lenticels between Japanese plum cultivars is required to understand why some cultivars are more prone to post-harvest moisture loss and shrivel. Different shrivel prone and non-prone cultivars were selected for various measurements

Peel permeability differed between farms, seasons, cultivars, orchards and developmental stage. The water vapour permeance of the peel was higher in susceptible cultivars, but not in all cases. Lenticel numbers differed between seasons and cultivars and clearly contribute to moisture loss, but differing between cultivars. Number of open lenticels could not explain all the variation in peel permeability.

Cuticular composition differed significantly between cultivars and seasons. 2,4-bis (dimethyl benzyl) phenol was present in high concentration in both cultivars. The combination of a rigid cuticle, due to high phenol content, fewer tri-hydroxy acids, and high primary alcohol content, and its smaller intercellular spaces, reduces ‘Songold’ cuticle deformation due to excessive postharvest moisture loss. Since the hypodermal cells of ‘Songold’ are closer together, their dehydration and collapse might not lead to significant shrinkage compared to the other cultivars. The cuticle is rigid, which means that it is less likely to collapse when the supporting cells underneath it shrink and collapse due to moisture loss.

Low-Density Poly-Ethylene packaging with 92 or 72 micro-perforations reduced moisture loss, while still preventing excessive in-package humidity, decay and chilling injury.

This study showed the complex interplay of different cuticle characteristics in response to or as a result of, moisture loss. Elucidating some of the mechanisms involved in the functioning and response of this complex biopolymer might enable manipulation of the cuticle to improve fruit quality and extend shelf life or to select and breed cultivars that are not prone to cuticular defects.