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 2.5 kPa compared with <1 kPa 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 <1 kPa CO2 than at 2.5 kPa CO2. Flesh browning was also higher at 1.5 kPa CO2 than at <1 kPa CO2, although ethylene production was lowest at 1.5 kPa 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 (<0.2 kPa 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 1-2 kPa O2/<1 kPa 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.