Modified Atmosphere Packaging Delays Senescence and Chlorophyll Degradation by Enhancing Antioxidant Capacity in Postharvest Broccoli

Fresh broccoli is highly perishable, exhibiting rapid yellowing and quality deterioration with a short shelf life. In this study, we investigated the effects of nanomaterial-modified atmosphere packaging (MAP) bags with different thicknesses, designated as 2.5C (25 μm) and 4C (40 μm), on the physiological and biochemical changes in broccoli were evaluated during storage at 20 ± 1 °C for 8 days. Results showed that both MAP treatments remarkably delayed floret senescence by inhibiting the rapid color transition from green to yellow, as indicated by alterations in L*, a*, b*, and hue angle values, as well as by suppressing chlorophyll degradation. The 2.5C treatment exhibited a more pronounced effect during storage. MAP treatments helped maintain commercial quality by preserving total phenols and vitamin C (Vc) content, retaining stem firmness and surface glossiness, regulating post-opening respiration rate and reducing water loss. MAP treatments also effectively suppressed the accumulation of superoxide anion (O2•−) and hydrogen peroxide (H2O2). Furthermore, MAP treatments enhanced free radical scavenging capacity, as demonstrated by DPPH and ABTS assays and the O2•− scavenging rate in broccoli. These results indicate that MAP treatment with an appropriate thickness (e.g., 2.5C) effectively inhibits excessive ROS production and enhances antioxidant capacity, thereby delaying floret chlorophyll degradation and senescence. This study provides a foundation for developing effective and green preservation strategies using physical MAP treatments for fresh broccoli.