Fruit maturity, controlled atmosphere delays and storage temperature affect fruit quality and incidence of storage disorders of 'Fuji' apples

The effects of storage temperature, harvest maturity, controlled atmosphere (CA) storage regime, and CA strategies on fruit quality and the incidence of storage disorders during storage of 'Fuji' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] were investigated. Flesh browning incidence was lower in fruit stored at 2°C than at 0°C, but fruit were also softer and had lower titratable acidity (TA) at the higher storage temperature. All subsequent studies were carried out at 0°C. High partial pressures of CO₂ (pCO₂) of 2.5kPa compared with <1kPa did not consistently affect flesh firmness, soluble solids concentration (SSC), and TA. The incidence of flesh browning was higher in more mature fruit and it was further aggravated by higher pCO₂ in the storage atmosphere, irrespective of pO₂, while watercore disappearance was more rapid at <1kPa CO₂ than at 2.5kPa CO₂. Flesh browning was also higher at 1.5kPa CO₂ than at <1kPa CO₂, although ethylene production was lowest at 1.5kPa pCO₂. Stepwise delay of high CO₂ or low O₂ CA storage did not affect flesh firmness, TA, internal ethylene concentration, respiration rate, and ethylene production, but watercore disappearance was more rapid, compared with standard CA storage at 2 months. Flesh browning was not detected in the stepwise CO₂ delayed CA treatment and low CO₂ CA storage (<0.2kPa CO₂), but a low (<4%) incidence of flesh browning was found in a delayed CA treatment and standard CA storage. These results indicate that 'Fuji' apples could be stored at 0°C in 1-2kPa O₂/<1kPa CO₂ if harvested at less than 190 days after full bloom. Stepwise CO₂ delay CA or low CO₂ CA storage regimes are recommended to retard the loss of fruit quality factors and reduce development of CA-related storage disorders.