Nitrogen modified atmosphere packaging maintains the bioactive compounds and antioxidant capacity of postharvest fresh edible peanuts

In the present study, fresh edible peanuts were packaged with nitrogen and oxygen (N2: O2 = 9:1) (modified atmosphere packaging, MAP) or air (control) and stored at 4 °C for 120 d. The physio-chemical properties, enzyme activities, and antioxidant capacity of fresh peanut kernels were analyzed at different time points during storage to investigate the effect of MAP on the preservation of this product. In comparison with control, the MAP treatment could efficaciously maintain the commodity characteristics of fresh edible peanuts by inhibiting the browning, increasing the firmness, and decelerating the accumulation of malondialdehyde and hydrogen peroxidase, the production of superoxide anion, and the electrolyte leakage rate of fresh edible peanut kernels. In addition, MAP-treated peanut kernels exhibited higher activities of the enzymes in the phenylpropanoid pathway, including phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and 4-coumarate-CoA ligase, and higher total phenolics, flavonoids and resveratrol contents. Activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase, and catalase, and antioxidant capacity [as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant potential (FRAP)] were also maintained in the MAP-treated kernels. Furthermore, positive Pearson's correlations were observed between FRAP and total phenolics (r2 = 0.93), total flavonoids (r2 = 0.91), and SOD (r2 = 0.95), as well as between DPPH and SOD (r2 = 0.89) and total flavonoids (r2 = 0.77). Our results therefore suggest that MAP is a promising strategy to enhance bioactive compounds accumulation and activities of antioxidant enzymes in fresh edible peanuts during postharvest storage, hence providing valuable insights into preserving this important protein source.