Pg. 21-25 Refinement of the sulphur-free litchi export protocol under laboratory and semi-commercial conditions

This project is being conducted to commercialise a preservative-free export protocol for South African litchis. During the 2003/04 season two trials were conducted under commercial conditions, one each with HLH Mauritius and McLean’s Red fruit. It was shown that it is possible and practical to pack preservative-free litchis, but the fruit is more vulnerable to breaks in the cold chain than sulphur fumigated fruit. Information generated earlier in the season with regards to fruit maturity and the use of 1-MCP was taken into account and a third laboratory based trial was conducted which incorporated 1-MCP. This brought about a significant improvement in fruit colour. We feel confident that a small export trial is now feasible, but this should be done under closely controlled conditions by researchers.

Summary:

• The project aims to commercialize a preservative-free export protocol for South African litchis during the 2003-04 season.
• Two commercial trials were conducted using HLH Mauritius and McLeans Red fruit to test the feasibility of packing preservative-free litchis, showing it is possible but the fruit is more vulnerable to cold chain breaks than sulphur-fumigated fruit.
• A third laboratory trial incorporated 1-MCP (a preservative agent) which significantly improved fruit color.
• Preference for a sulphur-free protocol involves keeping the litchi skin alive rather than using acid-based preservatives, which cause unnatural skin color.
• The preservative-free technique involves washing fruit in disinfectant, packing in polyethylene bags to prevent skin desiccation, but this creates challenges like fungal growth and skin browning.
• Earlier studies show 21 to 24 days of storage is achievable with preservative-free packing under commercial conditions.
• HLH Mauritius trial used larger 14 kg banana boxes with fruit packed in 30-micron polyethylene bags, showing practicality despite a break in the cold chain during transport.
• McLeans Red trial highlighted the importance of fruit maturity; over-mature fruit had shorter shelf life and higher fungal contamination.
• The use of 1-MCP was shown to inhibit fungal development and retain natural fruit color, especially important for fruit of the correct maturity.
• Fungicide Prochloraz was effective in reducing fungal infection but fungal growth still occurred rapidly once fruit was removed from cold storage, especially in over-mature fruit.
• The next phase involves exporting small consignments to Europe with strict handling instructions, including repacking into punnets after removal from plastic bags and refrigeration at the retailer.
• Harvesting protocols include early morning harvest, rapid packing, removal of damaged fruit, and using Smartfresh (1-MCP) before closing bags and cooling pallets.
• The article concludes preservative-free litchi packing is feasible with attention to cold chain, fruit maturity, and 1-MCP use to improve shelf life and color.