‘McIntosh’ and ‘Empire’ were maintained at 3 °C, and ‘Northern spy’ at 0 °C, under CA storage for 9 months. The CA storage regime for ‘McIntosh’ apples consisted of 2.5 kPa O2 + 2.5 kPa CO2 for one month, 3.5 kPa CO2 for the next month and then 4.5 kPa CO2 thereafter. ‘Empire’ and ‘Northern Spy’ apples were maintained in CA conditions of 2.5 kPa O2 + 2 kPa CO2 and 2.5 kPa O2 + 2.5 kPa CO2, respectively.
The CA system consisted of small aluminum storage chambers (0.9 m3 volume) fitted with a circulating fan system (Storage Control System Inc.). The atmospheric composition was checked automatically every hour and maintained within 0.2 kPa of the target values using an ICA61/CGS610 CA Control System (International Controlled Atmosphere Ltd., Kent, U.K.), which was modified with flow controllers for the experimental chambers (Storage Control Systems Inc.).