Mango sapburn: components of fruit sap and their role in causing skin damage.
Loveys B. R., Robinson S. P., Brophy J. J., Chacko E. K.
Author Affiliation: Division of Horticulture, CSIRO, GPO Box 350, Adelaide, SA 5001, Australia.
Australian Journal of Plant Physiology 19 : 449-457
Abstract : Damage caused to the skin of mango fruits by contact with sap exuded from the cut or broken pedicel reduces consumer acceptance and storage life of the fruits. Cv. Kensington fruits (particularly susceptible to sapburn injury) were collected, their pedicels broken and the fruits inverted to drain the sap. On centrifugation, the separation of the sap into 2 phases was hastened. When applied in 20-?l drops covering ~3 cm² of the skin of ripening, but still green fruits, skin damage was caused predominantly by the upper, non-aqueous phase. A major component of this phase was terpinolene which, when applied to fruit skins as above, resulted in symptoms indistinguishable from sapburn injury. The same type of damage was induced by synthetic terpinolene when applied undiluted, diluted in hexane or as an aqueous emulsion. Non-volatile sap components separated by distillation caused no skin damage. Sap from leaf petioles also contained terpinolene, but at a concentration 1% of that in the pedicel sap, and was not damaging to fruit skin. When the predominant terpene from cv. Irwin (less susceptible to sapburn) sap, car-3-ene, was applied to Kensington fruits, it caused significantly less damage than terpinolene. It was concluded that the primary cause of sapburn is the entry of volatile sap components through the lenticels, resulting in tissue damage and enzymatic browning.