Inhibition of superficial scald in apples by wounding: changes in lipids and phenolics

'Granny Smith' apples (Malus domestica Borkh) were wounded with a hypodermic needle or not prior to cold storage for 7 months at 0 degrees C. Wounded apples did not develop superficial scald adjacent to the wounded areas while non-wounded tissue developed scald on greater than 60% of the apple surface. Changes in conjugated trienes (CT) and membrane lipids that occurred as a result of scald formation were measured by examination of non-scalded tissue (achieved via wounding), scalded tissue on the same apple, and/or scalded tissue on the control fruit. Scald development was associated with an increase in CT and total glycolipid (GL) content, and a decrease in the proportion of linolenic acid (18:3) of the GL fraction and the GL unsaturation index (UI). These changes indicate that the chloroplast membrane is most affected by scald formation, possibly by the oxidative effect of CT. The reason for scald inhibition in the wound vicinity remains unknown. The increase in cinnamic acid derivatives in the wound area suggests an antioxidant activity. (C) 1997 Elsevier Science B.V.