Characterisation and induction of 'etch' browning in the skin of mango fruit

Abstract

The effects of detergents and mango sap on the development and anatomy of 'etch', a physiological skin disorder in mango (Mangifera indica L.) fruit, were examined. Etch was associated with a higher number of cracks in the cuticle than occurred in healthy tissue. Etch was induced on fruit dipped in the wetting agent Agral® at high concentrations (10, 50% v/v). Fruit kept in contact with pads saturated with low concentrations of detergents (Agral®, 0.1-1%; Amway LOC®, 0.1%) tended to develop etch at the perimeter of the contact area. Etch symptoms increased in severity with fruit ripening and increasing contact times with detergent. Lenticel spotting developed at lower detergent concentrations than were required for etch development. The oil, white oil/aqueous and blue lower aqueous components of mango sap were separated and applied to the skin of mangoes. No individual component resulted in more than mild perimeter etch. A 10:90 ratio of oil:aqueous fraction resulted in etch symptoms of moderate severity over the entire application area, but only when combined in wet contact with water or Agral®. The relevance of the results to mango postharvest handling systems is discussed.