Pg. 47-52 Litchi (Litchi Chinesis Sonn) Pericarp Colour Retention – Alternatives to Sulphur

The South African litchi industry is predominantly export orientated and pericarp (skin) colour retention is of primary importance, where export markets demand red fruit. Until now, gaseous sulphur treatments were thought to play a major role in the maintenance of this colour by firstly, fixing the anthocyanins, and secondly acting as a fungicide thus preventing browning reactions. Sulphuring of fruit however, results in undesirable aftertastes, constitutes a potential health problem and is ineffective against some fungi. In addition, since sulphur-fixed anthocyanins are colourless, the sulphuring process is sometimes reversed by dipping the fruit in low pH solutions. The pH of the solution is thus critical and detailed investigations have shown that a pH of 0,0, following blanching of the fruit in boiling water at 98°C, is most effective in retaining the red colour of the litchi pericarp for up to five weeks in storage at 1°C. Internal browning of the fruit flesh however, was observed and attempts at eliminating these were investigated.