- Lecille Tait and F J Kruger
- Institute for Tropical and Subtropical Crops, Private Bag X11208, Nelspruit 1200
- 1998
A study is being conducted, of which the main aim is to develop a suitable alternative to the currently used sulphur fumigation process. Evaluation of the pericarp colour retention and anti-fungal properties of a range of organic acids revealed that a tartaric acid treatment might possibly serve the purpose. Refinement of the treatment should include evaluations on the use of tartaric acid combinations and less concentrated applications. It was a/so found that dipping the fruit in a hot water solution containing imazalil might be effective. Combining the lmazalil treatment with an acid dip should, however, be further investigated. Additional post-harvest procedures, namely hydrocooling, modified atmosphere storage and ventilation restricting boxes did not seem to have practical application in the South African litchi export industry. Further research will concentrate on optimizing the organic acid treatments.
Summary:
- The study aims to develop suitable alternatives to sulphur fumigation, the current standard for preserving litchi fruit post-harvest, due to increasingly strict residue limits in the European market.
- Various organic acids were evaluated for their ability to retain pericarp color and provide antifungal properties; tartaric acid treatments showed potential for commercial use and warrant further research.
- Hot water dips with the fungicide imazalil showed promising results in controlling fungal infections, especially at higher concentrations and longer exposure times, comparable or better than sulphur fumigation.
- Packaging trials with reduced airflow cartons and modified atmosphere storage did not show practical advantages for the South African litchi export industry, as reduced ventilation could increase fungal infection risk.
- Hydrocooling did not significantly improve fruit quality or reduce fungal infection, offering minimal benefit considering the cost of the process.
- The study emphasized the need to further refine organic acid treatments to prevent crystallization on the fruit surface and optimize application concentrations and methods.
- Firmness, fungal infection rates, external appearance, mass loss, total soluble solids, and acid content were key evaluation criteria used in the experiments.
- Overall, tartaric acid and imazalil treatments are the most promising alternatives to sulphur fumigation, with further research required to optimize protocols and ensure residue safety.