Apples – improved quality and storability

Project manager: Ibrahim Tahir, Plant Breeding and Biotechnology, SLU

Several cultivars which have been chosen during last years to develop organic apple production in Sweden, had poor skin color at harvest and weak resistance to fungal decay and physiological disorders during storage.

The purpose of this work is to improve quality and storability of these cultivars by investigation of four possibilities:

•  multi- orchard practice
•  optimal harvesting date
•  postharvest treatments 
•  and ULO storage.

Pruning the trees and covering the orchard ground with white materials improve fruit color and storage potential due to better light distribution in the canopy, and more carbohydrate accumulation in the tree. An interaction between the effects of these two practices on the organic apples will be investigated.

Selection of the optimum harvesting date is one of the best ways to maintain fruit quality and minimize losses during storage. To make this selection accessible a maturity index for new cultivars that are produced in organic system will be developed.

Ultra low oxygen (ULO) storage is essentially based on delaying the natural ripening processes. Unfavorable ULO conditions can induce physiological disorders, enhance susceptibility to decay, and shorten shelf life. In this study, optimum levels of storage atmosphere composition for each cultivar will be estimated by keep fruits on four different oxygen and carbon dioxide percent for 16-20 weeks.

Heating which enhances the wound repair process, inhibits the synthesis of cell wall hydrolytic enzymes and changes skin structure has been used to control fungal decay and maintain fruit quality during storage. Ethanol is effective in reducing postharvest decay by disinfecting the fruit.

These two postharvest treatments also will be investigated by immersing organic apples in hot water (different degrees and periods) or treating them with ethanol.