Content, chemical composition and morphology of epicuticular wax of Fortune mandarin fruits in relation to peel pitting

Changes in the amount, chemical composition and morphology of epicuticular wax in relation to rindstaining and peel pitting of Fortune mandarin fruits from trees grafted on different rootstocks and growing in different locations in the citrus area of Valencia (Spain) were studied. The epicuticular wax amount was higher on fruits from the north quadrant of the tree and was more influenced by the orchard location than by the tree rootstock. The main constituent classes of the epicuticular wax were alkanes > esters > ketones > aldehydes > fatty acids > primary alcohols > triterpenes. In the north quadrant of the tree the alkane and ester content in the wax of fruits from an orchard with fruits not rindstained in recent years was higher and the ketone and fatty acid content was lower than in fruits from an orchard with fruits rindstained in recent years. The epicuticular wax of Fortune mandarin peel had an amorphous structure in which crystalline plates and platelets were inserted. The wax layer was more damaged in fruits from the rindstained orchard. The results obtained suggest (a) that damage to the epicuticular wax structure may be a factor that can influence rindstaining and peel pitting of Fortune mandarin fruits but is not a determining factor, and (b) that wax yield is not related to rindstaining and peel pitting of Fortune mandarin fruits. (C) 2000 Society of Chemical Industry.