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.