High O2/N2 controlled atmosphere accelerates postharvest ripening of ‘Hayward’ kiwifruit

Abstract

Kiwifruit (Actinidia deliciosa cv. Hayward) was exposed to high O2/N2 controlled atmosphere (30 % O2 + 70 % N2) for 7 d at 23 ± 1 °C to evaluate the effects on postharvest ripening and fruit quality. The treated fruit exhibited a dramatic increase in soluble solids content (SSC) and a rapid decrease in firmness and titratable acidity (TA), accompanied by a noticeable change in flesh color and volatile organic compounds during the first 7 d. Fruit exposed to high oxygen concentration required 7 d to reach the edible firmness (∼ 10 N), while the control fruit needed 42 d. At edible firmness, no differences in the SSC, TA, and flesh color were observed between treated and untreated kiwifruit, although the concentration and amounts of volatile organic compounds showed a little difference. High O2/N2 controlled atmosphere advanced respiration rate peak, with an increase in the contents of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP). The treatment also increased catalase (CAT) and peroxidase (POD) activities. Quantitative real-time PCR revealed increased expression levels of AdAAC1, AdAOX2, AcEXP1, AcPL1, AcPG, AcACS, AcACO, and AcACO2 in the treated fruit. Thus, the study's results indicate that high O2/N2 controlled atmosphere could accelerate kiwifruit ripening and result in good fruit quality.