MANGO SAPBURN - COMPONENTS OF FRUIT SAP AND THEIR ROLE IN CAUSING SKIN DAMAGE

Damage caused to the skin of mango fruit by contact with sap exuded from the cut or broken pedicel reduces consumer acceptance and storage life of the fruit. Mangoes of the Kensington cultivar are particularly susceptible to sapburn injury. On centrifugation, the fruit sap separated into two phases. Skin damage was caused predominantly by the upper non-aqueous phase. A major component of this phase was terpinolene which gave symptoms indistinguishable from sapburn injury when applied to the fruit surface. The same type of damage could be induced by the application of synthetic terpinolene when applied undiluted, diluted in hexane or as an aqueous emulsion. Non-volatile sap components separated by distillation were not damaging to mango skin. Sap exuded from the mango leaf petioles also contained terpinolene, but its concentration was less than 1 % of the concentration in pedicel sap and this sap was not damaging to the fruit skin. The Florida cultivar Irwin is less susceptible to sapburn injury and the predominant terpene in its sap was identified as car-3-ene. When applied to Kensington skin, car-3-ene caused significantly less damage than terpinolene. We conclude that the primary cause of mango sapburn is entry of volatile components of the sap such as terpinolene through the lenticels, resulting in tissue damage and subsequent enzymic browning.