Cold shock treatment with oxalic acid could alleviate chilling injury in green bell pepper by enhancing antioxidant enzyme activity and regulating proline metabolism

The effects of cold shock, oxalic acid, and combined cold shock + oxalic acid treatments on chilling injury, antioxidant enzyme activity, and proline metabolism of cold-stored green bell pepper fruit were investigated. The results showed that cold shock, oxalic acid treatment, and their combination significantly reduced chilling injury, inhibited the increase of superoxide radical production, hydrogen peroxide content, malondialdehyde levels, and relative membrane permeability, and increased antioxidant enzyme activity. Furthermore, the treatments promoted the accumulation of proline associated with increase in ∆1-pyrroline-5-carboxylate synthetase and ornithine δ-aminotransferase activities, and decrease in proline dehydrogenase activity. The results indicate that cold shock, oxalic acid, and their combination alleviated chilling injury in green bell pepper fruit by increasing antioxidant enzyme activity and proline accumulation. The combined cold shock + oxalic acid treatment was the most effective method for reducing chilling injury, and therefore has broad future application prospects.