REDUCED GREASINESS OF GRANNY-SMITH APPLES WASHED IN TWEEN-20 SOLUTION

'Granny Smith' apples (Malus domestica Borkh.) tend to develop greasy skins after extended storage which makes them slippery to touch and reduces their aesthetic appeal. Washing fruit in 0.15% (w/w) Tween 20 surfactant solution reduced greasiness, loss of greenness, and firmness after 22 days at 20 degrees C. These effects were associated with decreased skin permeance to gases, depressed internal oxygen (O-2) partial pressure and respiration, and increased internal partial pressure of ethylene, in washed compared to control fruit. Washing depressed the sum of O-2 and carbon dioxide partial pressures, suggesting that this treatment enhanced differential permeability characteristics of the fruit skin. Pre-treatment by wiping without using Tween 20 solution had none of these effects but stimulated weight loss. The potential for using a surface coating to delay the development of greasiness in stored apples should be re-examined.