Exogenous sodium nitroprusside treatment alleviates postharvest broccoli nutritional quality deterioration by mediating the ascorbic acid-glutathione cycle

Postharvest deterioration of the nutritional quality of broccoli limits the commercial value, resulting in a waste of resources. Here, broccoli was treated with sodium nitroprusside (SNP) to assess its effect on the main nutrients during the shelf life. The glucoraphanin, glucobrassicin, neoglucobrassicin, sulforaphane, and indole-3-methanol are the characteristic nutrient active components in broccoli. Their content decreased dramatically along with the prolongation of shelf life, especially glucoraphanin, with a loss rate of more than 55%. Nevertheless, SNP treatment significantly delayed the loss of the substances and controlled the loss rate of the above substances within 35%. The protective effect of SNP treatment on the nutritional quality of broccoli was also reflected in the accumulation of a higher abundance of ascorbic acid, free amino acids, total phenols, and total flavonoids in the SNP treated samples. It was further found that the effect of treatment in delaying the deterioration of nutritional quality may be attributed to the activation of antioxidant capacity by the treatment. The treatment activated the antioxidant enzyme activities in the ascorbic acid-glutathione cycle, mainly including ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase. Enrichment of ascorbic acid, glutathione, total phenols, and total flavonoids also proved that the treatment induced an increase in antioxidant capacity. The above results provide data support for the commercialization of SNP as a preservative.