Sodium nitroprusside preserves postharvest biochemical quality of sweet lime fruit by enhancing antioxidant capacity and reducing polyphenol degradation

Prolonged cold storage accelerates physiological and biochemical deterioration, thereby reducing the postharvest quality of sweet lime fruit. This study evaluated the effectiveness of sodium nitroprusside (SNP), a nitric oxide donor, in preserving the quality of sweet lime fruit during cold storage. Fruit were treated with SNP at five concentrations (0, 25, 50, 75, and 100 μmol L⁻¹) and stored at 7 ± 1°C and 85 ± 1% relative humidity for 150 d. Compared with the untreated fruit, SNP treatment significantly reduced weight loss (by 13.88%), maintained peel lightness (higher L values), suppressed decay incidence (by 14%), and maintained higher total phenolic and ascorbic acid contents. In addition, SNP treatment reduced polyphenol oxidase (PPO) activity while enhancing antioxidant capacity, as determined by the DPPH radical scavenging assay. Among the tested concentrations, 100 μmol L⁻¹ SNP was the most effective in preserving fruit quality throughout storage. These findings indicate that postharvest SNP application is a promising strategy for delaying quality deterioration and extending the storage life of sweet lime fruit under cold-storage conditions.