Superficial scald, a functional disorder of stored apples. II.—promoters and inhibitors

In confirmation of an earlier conclusion that volatile esters are not the major natural promoters of superficial scald, it has been shown I mole of butyl acetate in 5000 moles of air gave no increase of scald but produced a marked taint. Vapours of cyclohexane, cyclohexene, benzene and d‐limonene, and n‐hexadecane and hexadec‐I‐ene applied to the surface in ethanol solution reduced scald at suitable concentrations. The last three produced scald‐like injury at higher concentrations. During storage in oiled wraps, cuticle oil and ursolic acid were transferred to the wraps and mineral oil to the apples. A more volatile minor fraction of the mineral oil contributed to the control of scald. Diphenylamine gave better control of scald than N‐benzylaniline, dibenzylamine and dicyclohexylamine in decreasing order of effectiveness when used as dipping solutions in ethanol. Diphenylamine reduced volatile ester production at 1° but increased it at 20°, increased the production of less volatile esters of the lipid coating, and stabilised a pigment of the lipid coating. Quercetin reduced scald when applied to the fruit surface in ethanol solution, but cyanidin did not. The volatile‐agent theory of scald, the nature of the volatile agents, their means of escape, natural inhibitors and the mechanism of control by diphenylamine and oiled wraps are discussed.