Nitric Oxide in Controlled Atmosphere Storage of ‘Fuji Mishima’ Apples

‘Fuji’ apples require long-term storage to ensure year-round supply, and controlled-atmosphere (CA) technology is widely used to preserve their quality and reduce postharvest losses. Nitric oxide (NO), a natural signaling molecule in plants, has shown potential to delay ripening and reduce physiological and pathological disorders during fruit storage. This study evaluated the effect of nitric oxide (NO) treatment during controlled-atmosphere (CA) storage on the postharvest quality of ‘Fuji Mishima’ apples. Apples were stored for 8 months at 1 kPa O2 +< 0.5 kPa CO2, 1.0 ± 0.2 °C, and 94 ± 2% RH. The treatments consisted of a control (without NO) and five NO application regimes: 5 µL L−1 applied at the beginning of storage; 5 µL L−1 applied both at the beginning and end; 5 µL L−1 applied every 30 days; 10 µL L−1 applied at the beginning; and 10 µL L−1 applied both at the beginning and end of storage. All NO treatments delayed ethylene production and reduced its levels after 4 days under ambient conditions compared to the control. However, NO had no effect on flesh firmness, soluble solids content, titratable acidity, peel color, or flesh browning. Repeated NO applications (5 or 10 µL L−1) increased peel yellowing. Treatment with 5 µL L−1 applied every 30 days increased decay incidence. Phenolic compounds in the flesh were unaffected, while in the peel, they decreased with 10 µL L−1. Overall, NO application in CA storage of ‘Fuji Mishima’ apples did not maintain fruit quality and, in some cases, increased peel yellowing and decay.