Mechanism of Action of Exogenous Sodium Nitroprusside Treatment in Alleviating Pericarp Browning of Refrigerated ‘Nanguo’ Pear Fruit

Abstract

To investigate the regulatory effect and possible mechanism of exogenous sodium nitroprusside (SNP) treatment on the pericarp browning of refrigerated ‘Nanguo’ pear fruit, the effect of 1.0 mmol/L SNP pretreatment on the pericarp browning of ‘Nanguo’ pear fruit during shelf life at room temperature after 180 days of refrigerated storage was investigated. The results showed that browning symptoms appeared in the SNP-treated fruit three days later than the control fruit, and at the end of the shelf life, the browning incidence and browning index were 41.8% and 31.9% of those of the control fruit, respectively. The treatment protected the structural integrity of pericarp cells and inhibited the elevation of membrane permeability. Further analysis revealed that at the end of the shelf life, the superoxide anion, hydroxyl and 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical scavenging capacity of the SNP-treated fruit were 1.65, 1.13, and 1.24 times higher than those of the control fruit, respectively. Meanwhile, the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) was significantly reduced, which was 25.2% and 32.8% lower than that of the control group, respectively, and the activities and gene expression of polyphenol oxidase and peroxidase were 17.5%, 28.8%, 37.5% and 39.2% lower than those of the control group, respectively. In addition, the synthesis of phenolics was inhibited to some extent. In conclusion, SNP treatment could alleviate the occurrence of pericarp browning in refrigerated ‘Nanguo’ pear fruit by inhibiting membrane lipid peroxidation and maintaining cellular structural integrity and function.

Keywords

• ‘nanguo’ pears; pericarp browning; sodium nitroprusside; membrane lipid peroxidation; cellular structure