The aim of his study was to explore the impact of dielectric barrier discharge cold plasma (DBD-CP) treatment on the phenolic metabolism of stored rice under high-temperature stress.

Under simulated summer high- temperature conditions (35 ℃), fresh high-moisture rice (Japonica rice, 16.0% moisture content on a wet basis) was used as the raw material, the effects of DBD-CP treatment on quality parameters such as L^*, a^*, b^*, yellowness index (YI), reactive oxygen species, and malondialdehyde (MDA) in stored rice were analyzed. Additionally, the study aims to analyze the changes in total phenols, total flavonoids, and antioxidant activities during the storage process. The investigation would involve multiple validations, including ABTS⁺ and DPPH radical scavenging activities, ferric ion reducing power, and the activity changes of key rate-limiting enzymes in phenylpropane metabolism. The ultimate goal was to explore the impact of DBD-CP treatment on the phenolic metabolism of stored rice.

After DBD-CP treatment, the color stability of rice during storage significantly improved. The yellowing index of the treatment group decreased significantly by 12.6% after 60 days of storage. After 20 days of storage, the levels of superoxide anion, hydrogen peroxide, and MDA decreased by 14.8%, 41.6%, and 21.6%, respectively, and the deterioration rate of fresh high-moisture rice was significantly inhibited. Additionally, during the high-temperature stress storage period, the total phenol and total flavonoid content in the treatment group increased simultaneously (P<0.05), with maximum increases of 1.23 and 1.34 times, respectively. The antioxidant properties and iron ion reduction capacity of the corresponding samples were also improved (P<0.05). Combined with the analysis of the activity of key limiting enzymes in phenylpropane metabolism, the activities of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H), and chalcone synthase (CHS) were significantly enhanced, with increases ranging from 1.71 to 2.28 times. Further correlation analysis confirmed the close association (P<0.05) between the content of phenolic substances in high-moisture rice under high-temperature stress and the activities of PAL, C4H, and CHS enzymes, and a significant negative correlation (P<0.05) with internal reactive oxygen species and MDA content.

Dielectric barrier discharge cold plasma treatment could promote the synthesis rate of phenolic compounds within the grains of high-moisture rice by activating phenylpropane metabolism. This treatment enhanced the tissue's antioxidant properties, alleviated membrane lipid peroxidation, and reduced the accumulation of free radicals. As a result, it delayed the quality deterioration of rice under high-temperature storage conditions.