REDUCTION OF SUPERFICIAL SCALD OF APPLES WITH VEGETABLE-OILS

Five vegetables oils were applied by hand to Granny Smith apples that were highly susceptible to superficial scald and stored at 0 degrees C for several months. A petroleum-derived 'baby oil' was included for c omparison. Sunflower oil was applied in two seasons. Canola, castor, p alm, peanut and the purified petroleum oil were used in a single seaso n. All oils considerably reduced scald without causing injury. Two dro ps of oil (approximately 25 mg) had marked effects on the severity of superficial scald. The severity of the disorder was related logarithmi cally to the number of drops of oil applied. The regression equation w as: Scald score = 2.24 - 0.73 log(e) (no. of drops). However, oils wer e not significantly different in their effects on scald. Thus scald co ntrol by the different oils does not appear to be related to chain len gth of fatty acids or degree of unsaturation. A physical effect may be responsible for the control of superficial scald by the six oils. App les treated with castor or palm oil remained greasy even after storage for several months. The other oils were far less greasy and when appl ied in,low doses there were little observable differences in greasines s compared to the controls. Canola, peanut and sunflower oils appear t o have possibilities as commercial scald control agents. Baby oil woul d probably be unacceptable due to its petroleum origin. The testing of a greater range of vegetable oils on other apple cultivars is worth f urther investigation.