High concentrations of carbon dioxide influence kiwifruit ripening

Abstract

Kiwifruit were exposed to air, 60% carbon dioxide or 80% carbon dioxide (balance 20% oxygen and nitrogen) for 1, 2 or 3 weeks at 0°C, then stored in air for up to 8 weeks at 0°C. The effects on kiwifruit ripening (softening and increase in soluble solids), were determined. Respiration and ethylene production were measured during 1 week at 20°C immediately after the exposure to high carbon dioxide, and after 8 weeks subsequent air storage. Both 60% and 80% carbon dioxide atmospheres produced the same effects. One week exposure to high carbon dioxide temporarily retarded fruit softening, but differences in firmness had disappeared after 8 weeks air storage. During 1 week at 20°C immediately after the carbon dioxide treatments, rates of respiration and ethylene production were high and fruit softened quickly. After 8 weeks of air storage, rates of respiration and ethylene production at 20°C were restored to the control rates and ripening appeared normal. Levels of soluble solids in the fruit after 8 weeks of air storage were lower at a result of 2 weeks of high carbon dioxide treatment, but in all treatments, after 1 week at 20°C, soluble solids levels had increased and were similar to those in the controls. Rates of respiration and ethylene production were usually higher immediately after the longer carbon dioxide treatments, and after 8 weeks air storage. Both 2- and 3-week treatments dramatically increased the incidence of storage rots. Kiwifruit appear to tolerate 1 week of high carbon dioxide treatment providing they have a period of air storage immediately after the treatment.