Conjugated triene oxidation products of alpha-farnesene induce symptoms of superficial scald on stored apples.

The sesquiterpene alpha-farnesene (1) and its conjugated triene oxidation products accumulate in the skin of apples after harvest and are implicated as the causal agents of superficial scald. Conjugated triene oxidation products and analogues were synthesized and applied to the surface of Granny Smith apples either as vapors or in squalane. Farnesyl hydroperoxide (2a), trienol (2b), endoperoxide (3a), dehydronerolidol (5), and cumyl hydroperoxide (4) all produced the symptoms of superficial scald when applied at nanomolar doses. Scald-inducing activity was dependent on the mode of application. Farnesyl hydroperoxide (2a) was the most active conjugated triene when applied directly to the apple skin. Trienol (2b) also induced scald symptoms and partially reversed the inhibition of scald caused by diphenylamine.