- S A Oosthuyse
- HortResearch SA, PO Box 3849, Tzaneen 0850, South Africa
- 2007
Coating Madras litchis with a polymer formulation was assessed as a measure to prevent or limit moisture loss and Penicillium colonization during and after extended cold-storage. The fruits were stored at 1°C for 28 days, and were subsequently evaluated 8 and 10 days after cold-storage; the evaluations taking place at ambient temperature. Export cartons of Madras litchi fruits were coated with PolymerCoat directly after packing. The fruits were harvested and sulphured the day before treatment. PolymerCoat was applied at 25, 50, 75 or 100% concentrations. Uncoated fruits served as controls. PolymerCoat was effective in reducing moisture loss during cold storage and inhibiting Penicillium fruit colonization, particularly when applied at full strength. Ninety-five percent of the fruits treated at full strength were devoid of Penicillium 10 days after cold-storage – 39 days after harvesting. Weight loss during coldstorage was reduced by 5%. Taste appeal and juice total soluble solids content were reduced by coating, but not to levels resulting in lesser appeal. Coating appeared be greatly beneficial as a treatment for Madras fruits destined to be exported by sea to the EU. Coating at full strength might be recommended. Further assessment is required for result confirmation, as well as to determine the influence maturation stage or fruit source may have regarding effect.
Summary:
- Madras litchis exported to the EU typically suffer from browning, visible shrinkage, exudation, weight loss, and heavy Penicillium colonization after 21–28 days at about 1°C, making quality retention a major challenge.
- Export cartons of commercially harvested and sulphured Madras litchis were dipped in PolymerCoat at 25%, 50%, 75% or 100% strength, with uncoated fruit serving as the control, then stored at 1°C for 28 days and evaluated for 8–10 days at ambient temperature.
- PolymerCoat treatment clearly reduced moisture loss during and after cold storage, with weight loss dropping from about 17% in uncoated fruit to roughly 12.5% when PolymerCoat was applied at full strength.
- Coated fruits showed much less visible shrinkage and exudation than uncoated fruits, indicating that reduced moisture loss also limited the surface conditions that favor Penicillium growth.
- Penicillium colonization was strongly suppressed by PolymerCoat, with about 93–95% of fruits coated at full strength remaining free of Penicillium 8–10 days after cold storage, while all uncoated fruits were colonized and often severely infected.
- The degree of Penicillium infection was inversely related to PolymerCoat concentration, with higher coating strength giving better protection and virtually no severe colonization at 50% strength or higher.
- Although coating slightly reduced taste appeal and juice total soluble solids content compared with the control, coated fruits were still rated acceptable and generally appealing in both taste and appearance.
- Overall, PolymerCoat was deemed highly beneficial for maintaining visual quality and limiting decay of sulphured Madras litchis destined for long-duration sea export to the EU, with full-strength coating suggested as a promising option.