# Study on the Changes of Antioxidant System and Respiratory Metabolism in Rice Grains Under Nitrogen-Modified Atmosphere Storage from the Targeted Metabolomics Perspective

## TL;DR

This study shows how storing rice in a nitrogen-rich environment helps preserve its quality by reducing oxidative damage and improving metabolism.

## Contribution

The novel contribution is the targeted metabolomics analysis of how nitrogen-modified atmosphere affects antioxidant and carbon metabolism in stored rice.

## Key findings

- Nitrogen-modified atmosphere reduced fatty acid value and reactive oxygen species in stored rice.
- Antioxidant enzyme activities like SOD, POD, CAT, and GR were higher under nitrogen-modified atmosphere.
- Metabolomic changes included up-regulation of key carbon metabolism metabolites like fructose 6-phosphate and glycerol 3-phosphate.

## Abstract

Nitrogen-modified atmosphere technology, due to its effectiveness in pest control, is widely used in grain storage as an eco-friendly preservation method. This study compared the quality changes in unhulled rough rice (paddy) stored under nitrogen-modified atmosphere and conventional conditions. Fatty acid value (FAV), reactive oxygen species (ROS) content, coenzyme levels, antioxidant enzyme activities, and concentrations of central carbon metabolism-related metabolites of paddy were monitored during storage under different storage conditions. The results revealed that compared to conventional storage, nitrogen-modified atmosphere resulted in lower FAV and ROS levels, as well as higher pyridine nucleotides contents and antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione reductase (GR). Metabolomic profiling demonstrated that N2-MAS induced metabolic changes characterized by the down-regulation of 2-hydroxyglutaric acid and the up-regulation of fructose 6-phosphate, glucose 1-phosphate, glycerol 3-phosphate, gluconic acid, fumaric acid, and malic acid, which collectively contribute to reduced oxidative damage and enhanced preservation quality. These findings elucidated the mechanism of N2-MAS-delayed quality deterioration and revealed the regulatory role of the antioxidant system and central carbon metabolism.