ESTIMATION OF APPLE FRUIT SURFACE-AREA

Surface areas of fruits and vegetables are often estimated by assuming that they resemble a shape from which surface area can be mathematica lly calculated. Two such models, sphere and ellipsoid, were compared t o three alternative approaches for estimating surface areas of apple f ruit (Malus domestica Borkh.) of four cultivars ('Royal Gala','Braebur n', 'Red Delicious', and 'Granny Smith'). Sphere and ellipsoid models underestimated actual surface area by 15 and 18%, respectively, with p oor correlation between predicted surface area and actual surface area (estimated by measuring the area of adhesive tape required to cover t he fruit surface). A method based on finite elements marginally overes timated surface area but reliably predicted surface area of small 'Roy al Gala' and 'Braeburn' apples and had reasonably close correlation wi th actual surface area. Non-linear regression models, developed from t he very strong correlation between actual surface area and both fruit mass and volume, were the most accurate predictors of fruit surface ar ea of the methods tested.