This practice continued, with varying degrees of success, until the discovery of the scald-control properties of antioxidants. These scald-inhibiting chemicals apparently act to prevent oxidizing enzymes from killing and browning the apple skin. For maximum effectiveness, the materials should be applied to the fruits within a week after harvest. For most varieties, scald control is reduced with each additional week of delay in applying the inhibitor. The materials can be applied as postharvest sprays, dips, or impregnated paper wraps.
Thorough coverage is essential to good control.
With some varieties preharvest sprays with scald inhibitors are effective. If preharvest sprays are used, then postharvest applications should be omitted because of the danger of accumulating a chemical residue in excess of the legal tolerance. Varietal differences have been found in the effectiveness of chemicals for control of ordinary scald. For example, Winesap apples respond well to both ethoxyquin and diphenylamine, whereas the Delicious variety responds poorly to ethoxyquin but diphenylamine is effective in the control of ordinary scald. In addition to the use of scald inhibitor chemicals, air purification units may also be used to absorb volatiles.