Postharvest hypoxia and anoxia stresses delay anthocyanin accumulation in cold-stored blood orange fruit

The effect of different gas compositions on bioactive compounds, antioxidant activity, and quality of ‘Moro’ blood orange fruit during cold storage was investigated. The fruit were kept at 10 °C in hermetically closed chambers (190 L) with different gas compositions, including 1) normal air, 2) 20 % CO₂ in air, 3) 30 % CO₂ in air, 4) 20 % CO₂ in N₂, 5) 30 % CO₂ in N₂, and 6) 100 % N₂, for 21 days. Weight loss and firmness loss increased across all treatments. However, fruit stored in CO₂-enriched atmospheres exhibited significantly lower weight loss and better firmness retention compared to those stored in normal air. Total soluble solids (TSS) remained stable, but titratable acidity (TA) decreased, particularly in normal air, leading to the highest TSS/TA ratio in this treatment. Sucrose levels increased in treatments containing O₂ and decreased under O₂-depleted (anoxic) conditions by day 14. Glucose and fructose concentrations initially increased, particularly in normal air and 30 % CO₂ conditions and were lowest in the 30 % CO₂ in N₂ treatment. The highest levels of total anthocyanin content (TAC), total phenolic content (TPC), and total antioxidant activity (TAA) were observed in normal air. Storing blood oranges in normal air was most effective in enhancing TAC, TPC, TAA, and juice quality during storage. However, CO₂-enriched conditions were more effective in maintaining physical qualities. Overall, fruit quality in treatments containing O₂ was better than in those stored under O₂-depleted (anoxic) conditions, suggesting that O₂ promotes the enhancement of bioactive compounds, especially anthocyanin, in cold-stored blood oranges.