Investigate the effect of cooling and delays as well as CO2 concentrations during storage on internal browning in ‘Fuji’ apples

Controlled atmosphere (CA) storage increases the availability of high-quality fruit but can cause physiological defects, e.g. internal browning (IB). The aim of the project was to determine the effect of cooling, delays, and CO2 concentrations during storage on fruit physiology in order to develop optimum cooling regimes for ‘Fuji’ apples.

Three trials investigated the effects of 1) stepdown cooling and storage duration 2) delayed  cooling, delayed CA establishment and storage times and 3) CO2 concentrations on internal browning. Fruit quality evaluations were done after each storage period, after shipping and handling and after shelf-life.

‘Fuji’ harvested at optimum maturity promoted bitter pit but prevented CO₂ injury under CA. Cooling delay of 28 h and stepdown cooling caused ethylene accumulation that promoted bitter pit. ‘Fuji’ room cooled at 0.5 °C immediately after harvest and stored for >4 months in CA managed the fruits’ sensitivity to ethylene and bitter pit development.

Fuji’ harvested at optimum maturity, room cooled at 0.5 °C immediately after harvest and CA-stored for >4 months prevented CO₂ injury and bitter pit. Stepwise cooling is not recommended. A short-term high CO₂ and low O2 stress after harvest cannot be used to predict CO2 injury during long-term CA storage.

Harvest fruit at optimum maturity to prevent CO₂ injury. Stepwise cooling is not recommended. Store fruit for longer than 4 months to reduce bitter pit expression.