Pg. 50-54 The effect of temperature management on retention of litchi colour and quality

The majority of litchi fruit produced in South Africa is treated postharvest with sulphur to decrease fruit browning and control postharvest diseases. However, 97% of exported fruit are sold to the European Union, which has deemed sulphur to be unacceptable. Alternative forms of fruit quality maintenance are thus necessary. The primary cause of fruit postharvest browning is believed to be desiccation. Previous work using PVC bag packaging has, however, resulted in enhanced postharvest fungal decay, due to excessive condensation. In this study fruit was packaged in polypropylene bags, with specific anti-mist and gas exchange properties. Static and hydrocooling methods were tested and for postharvest decay control, a bacterial compound was tested. Fruits were stored at 1 °c and 5.5°C for 40 days, with evaluations at 10 day intervals. Packing in bags significantly reduced fruit water loss and enhanced retention of fruit colour for up to 20 days. There was no advantage of hydrocooling over standard static cooling, however, most water loss occurring in the first 10 days of storage. Total soluble solids of packaged fruit decreased with storage but remained high (15 to 20° Brix) while acidity was poor at below 0.40%. The TSS: acid ratio showed good eating quality as it remained between 31:1 and 60:1. Fruit that was hydrocooled and stored at a temperature of 5.5°C without a Biosave treatment showed a statistically superior colour which remained good for up to 40 days of storage. The higher storage temperature showed better colour retention, however, there was greater incidence of disease.

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