Pg. 14-20 Determination of maturity cut-off points for South African export litchi fruit

A study is being conducted, aimed at the development of appropriate harvest window cut-off points for HLH Mauritius and McLean’s Red export litchis. It was found that sulphur fumigated HLH Mauritius litchis contracted relatively few fungal infections during export simulations when the TSS/TA ratio was lower than 30:1. The incidence of infection dramatically increased when the TSS/TA ratio became higher than 30: 1. In the case of McLean’s Red, it was more difficult to establish an exact cutoff value. The infection rate of this cultivar was found to increase linearly by approximately 2% for every 1 unit increase in the TSS/TA ratio. The over-mature McLean’s Red litchis also had significantly higher SO2 residues in the aril of the fruit. Based on the current results, it is recommended that sulphur fumigated South African HLH Mauritius and McLean’s Red litchis are exported between TSS/TA values of 20:1 and 30:1. Further research is to be conducted to establish to what extent the above parameters can be stretched. This will primarily involve the use of slow release sulphur dioxide sheets and controlled atmosphere (CA).

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