Nitrogen-modified atmosphere and re-aeration storage induce differential responses of antioxidant system linked to rice quality: An untargeted metabolomics study

Nitrogen-modified atmosphere storage (N 2 -MAS) is a common grain preservation technique. However, previous studies had shown that the quality of paddy rice after N 2 -MAS deteriorated more rapidly. To reveal the mechanism of this phenomenon, the antioxidant indicators of two rice varieties during high-concentration (HNM-RS, nitrogen volume fraction of 0.99) and low-concentration (LNM-RS, nitrogen volume fraction of 0.95) nitrogen modified atmosphere and re-aeration storage were investigated in this paper. It was shown that after re-aeration, the N 2 -MAS groups exhibited accelerated increases in fatty acid value (FAV), malondialdehyde (MDA) content, and electrical conductivity (EC). Antioxidant system analysis Faster declines in superoxide dismutase (SOD), peroxidase (POD) activities, glutathione (GSH), and total phenolics (TP) contents, as well as enhanced accumulation of superoxide anion (O 2 ‧ − ) and hydrogen peroxide (H 2 O 2 ) were proven in the N 2 -MAS groups. It was further demonstrated that in the conventional storage (CS) group, the levels of antioxidant-related compounds—such as shikimates and phenylpropanoids (iristectorin B, etc.) and terpenoids (obacunone, etc.) were significantly up-regulated, whereas the contents of fatty acid peroxidation products (13(S)-HODE, etc.) associated with oxidative stress were significantly down-regulated by untargeted metabolomics. The results provided a physiological and metabolic basis for optimizing storage strategies to maintain rice quality. • Rice in HNM-RS and LNM-RS deteriorated more rapidly than CS. • Re-aeration caused more oxidative damage than CS. • The antioxidant-related metabolites were up-regulated in CS group vs. RS group. • Lipid peroxidation products were down-regulated in the CS group vs. RS group.