- J A Duvenage1 , M M Mostert2 and J J Marais1
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1Merensky Technological Services, PO Box 14, Duivelskloof 0835
2Department of Horticulture, University of Pretoria, Pretoria 0001 - 1995
Litchi fruit (cultivars Mauritius and Madras) were treated after harvest with sulphur compounds and low pH dips, or calcium nitrate dips. After storage the fruit were evaluated for postharvest diseases, browning, colour and taste, and were analysed for SO2 residues. Sodium metabisulphite dip or SO2 fumigation, followed by hydrochloric acid dips, delivers fruit of superior quality to SO2 fumigation treated fruit only. Treatment of fruit with calcium nitrate followed by hydrochloric acid dip gave promising results (while no sulphur compound is used).
Summary:
- The study evaluated postharvest treatments on litchi fruit cultivars Mauritius and Madras to retain red skin color, reduce browning, disease, and maintain taste.
- Treatments tested included sodium metabisulphite dips, SO2 fumigation, low pH (hydrochloric acid) dips, calcium nitrate dips, and combinations thereof.
- Sodium metabisulphite dip (60 g/l for 10 min) or SO2 fumigation (600 g sulphur/ton) followed by hydrochloric acid dips (pH 4 for 3-5 min or pH 1.2 for 10 min) produced superior fruit quality compared to SO2 fumigation only.
- These treatments resulted in significantly less browning and postharvest disease and better retention of red skin color.
- Calcium nitrate dip followed by hydrochloric acid dip also showed promising results, with the advantage of no sulphur residues.
- SO2 residues in treated fruit pulp were within acceptable limits, with some treatments showing zero residue.
- Taste was generally acceptable across treatments, with no significant negative effects noted.
- Use of plastic bag packaging for moisture retention led to browning and severe diseases, so was not recommended.
- The study supports use of low pH dips following sulphur treatments to enhance fruit appearance and reduce postharvest problems.
- Not rinsing fruit with water after treatment seemed to improve outcomes.
- The research confirms earlier findings and provides potential commercial postharvest treatments for maintaining litchi fruit quality during storage.