Oxygen stress of 'Granny Smith' apples in relation to superficial scald, ethanol, α-farnesene, and conjugated trienes

Abstract

Granny Smith apples were exposed to 2 levels of oxygen stress, <1% O2 at 0°C or <0 ·01% O2 at 20°C before storage at 0°C. Stress duration was 2-16 weeks at 0°C and 1-10 days at 20°C. The severity of superficial scald decreased as the period of O2 stress was increased. The amount of ethanol in the juice increased as the period of O2 stress increased. The accumulation of a-farnesene and conjugated trienes in the wax proceeded in all treatments but the amount of increase become less as the period of O2 stress was extended. Superficial scald was eliminated with an 8-day period of O2 stress at 20°C before cold storage or with 16 weeks O2 stress at 0°C. It is suggested that control of scald by O2 stress may be due to increased production of ethanol and consequent reduction of a-farnesene and conjugated trienes accumulation.