Pg. 59-69 Effect of the addition of prochloraz to PolymerCoat on weight loss and mould colonization during and after extended cold storage of sulphured and non-sulphured Madras litchi fruits

Late harvested Madras litchi fruits were coated with PolymerCoat at full-strength (100%), 50% or 10% strength, to which Chronos (prochloraz) at 18 or 36 ml per 10 f PolymerCoat was added. Treatments were individually applied to all of the fruits in 2 kg cartons shortly after harvesting. After treatment, the fruits were held at 3°C for 38 days and subsequently at 20°C for a further nine days (47 days of storage). Two identical experiments were carried out, one on sulphured and the other on non-sulphured litchis. Each experiment comprised the six treatment combinations (factorial arrangement) and an untreated control. There were 10 single-carton replicates in a Randomized Complete Blocks experiment design. Weight loss, mould incidence, and skin browning were monitored and quantified during the storage period. Taste and indentation incidence were quantified on termination, nine days after cold storage. 

In the sulphured fruits, weight loss bore no apparent relation to treatment, and was of the order of 18.5% during the storage period. PolymerCoat application at full-strength was highly effective in preventing mould colonization and fruit indentation. Efficacy was reduced where PolymerCoat was diluted. Differences in colonization relating to prochloraz application rate were not apparent. Taste was positively affected by coating. Fruit browning or darkening did not occur. T he fruits treated with 100% PolymerCoat were acceptable for consumption after the storage period. In the non-sulphured fruits, weight loss in the untreated fruits was greatest during storage, being of the order of 21%. In the coated fruits, differences in weight loss relating to treatment were not clearly apparent. In the coated fruits, average weight loss was in the order of 17.3%. Skin browning occurred during cold storage. It was slightly delayed in the coated fruits treated with prochloraz at the lower rate. PolymerCoat application at full-strength was effective in suppressing mould colonization during cold storage, and preventing fruit indentation during the storage period. Efficacy was reduced when PolymerCoat was diluted. Differences in mould colonization relating to prochloraz application rate were not apparent. Taste was positively affected by treatment, but was generally unappealing.

PolymerCoat application at full-strength to sulphured Madras litchi fruits during packing was recommended for
commercial evaluation or adoption.