The Postharvest Section of the ARC-ITSC is primarily involved in two fields of research. The first concerns the development of appropriate protocols to enable the exportation of subtropical produce by sea. The second concerns the identification and subsequent rectification of physiological disorders that occur during storage. A significant proportion of these disorders are caused by preharvest aspects such as climatic conditions and the horticultural practices applied by the producer. The present summary aims to provide one example of each of the above fields of research.
In so far as the development of export protocols is concerned, one of the major problems encountered by South African avocado exporters is the softening of fruit while in transit. Because of this, the produce needs to be sold immediately upon arrival. Not only are the importers then forced to sell the fruit at lower prices, but the price of avocados already on the market is deflated. As a consequence, exporters take extreme care to ensure that avocado fruit land in a hard state. A number of techniques are employed to prevent the fruit from ripening while being transported. The first line of defence is to store the fruit at a low as possible temperature. In addition to this, the avocados are stored under either controlled atmosphere (CA) or modified atmosphere (MA). With both these techniques, the oxygen content of the atmosphere is artificially decreased while the carbon dioxide content is increased. During the last 5 years, the ARC-ITSC has been involved in the commercialisation of Smartfresh (1-methyl cyclopropene), an exciting new tool to ensure hard landings. Introduction of the technology to the South African avocado industry has resulted in a substantial reduction in export costs. This has been of great strategic importance in light of shrinkage in profits that occurred due to the strengthening rand as well as increased competition from South America.
On so far as the preharvest quality management is concerned, the section has made a major contribution towards reducing the mesocarp discoloration problem of avocados which annually causes significant losses during storage. Recommendations to alleviate the problem centred on preharvest aspects such mineral (especially nitrogen) nutrition and harvest maturity. One of the key research procedures involves mineral analysis of the fruit as from fruit set until harvest. The mineral composition of the pulp and rind is then linked with climatic and horticultural practices and specific recommendations are made based on the observed trends.