Pg. 44-47 A Comparison of Different Postharvest Treatments and Packing Materials for McLean’s Red Litchi Fruit

Fumigation with sulphur dioxide (SO₂) is the standard postharvest treatment of export litchi fruit from South Africa, but fruit sulphur residue limits in France, the major importer of South African litchis, are strict and have recently been reduced. Alternative postharvest treatments, viz SO₂ + 1 N HCI dip, 2 s steam (95°G) + 1 N HCI, and 2 s steam + 1 N HCI + Vapor Gard® (an anti-transpirant), were compared to untreated controls and standard SO₂ treated fruit of the cultivar McLean’s Red. Fruit from these five postharvest treatments were packed in standard ventilated cartons, pun nets wrapped in Vitafilm®, or P-Plus® polypropylene bags, and stored for 28 days at 1°C to simulate sea export. Ventilated cartons resulted in excessive moisture loss (13.5%) during storage, compared to Vitafilm® (1.33%) and P-Plus® (0.25%). Untreated control fruit had severe skin browning but were firm and tasted good. SO₂ treated fruit (industry standard treatment) were also firm and had good taste, but colour was an unattractive dull pink. A four minute dip in 1 N HCI following SO₂ fumigation resulted in an attractive red colour, but fruit were slightly less firm than fruit treated with SO₂ fumigation alone. Two seconds of steam followed by 1 N HCI dip resulted in attractive red fruit, but some steam (or HCI) scalding was evident and fruit were soft with poor flavour, when compared to untreated control and SO₂ treated
fruit. Vapor Gard® had little positive effect on steam and HCI treated fruit. Further research is required to improve the postharvest treatment of McLean’s Red litchi fruit.