Inhibitory mechanism of low-oxygen-storage treatment in postharvest internal bluing of radish (Raphanus sativus) roots

Oxidative stress in radish roots causes internal blue discoloration and decreases vegetable quality. Accordingly, the effects of different oxygen concentration treatment on this coloration during storage was investigated; 4-hydroxyglucobrassicin content (a precursor of the blue component); the reactive oxygen species (ROS) superoxide (O2-) and hydrogen peroxide (H2O2); the antioxidants ascorbic acid (AsA) and glutathione (GSH); and the activities and gene expression levels of the enzymes catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), were monitored under normal and low-oxygen conditions. The results indicated that packaging radish roots under 10% O2 prevents blue discoloration by decreasing the activity and expression of the oxidant enzyme POD, increasing the levels of antioxidant and reducing substances, and upregulating antioxidant enzymes, all of which act to decrease the generation of ROS (O2- and H2O2).