Abstract: We investigated changes in the phenolic composition of Dongfanliang millet produced in Shanxi province before and after being cooked into porridge. The cooking process was optimized by orthogonal array design. Phenolic compounds were extracted from raw millet and millet porridge and analyzed by widely-targeted metabolomics, and their antioxidant capacities were determined. The results showed that the optimal parameters were as follows: cooking time 15 min, cooking power 700 W, and solid-to-liquid ratio 1:25 (g/mL). Compared with raw millet, the contents of free phenol and bound phenol in millet porridge decreased by 53% and 10%, respectively. The free and bound phenolic compounds from millet porridge scavenged 75.41% and 56.54% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, and their total antioxidant activities were 14.72 and 9.58 U/mL, respectively. A total of 37 polyphenols were identified by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS). Nineteen of these were found to be differential between the samples and 10 metabolic pathways were identified by KEGG pathway enrichment analysis. After being cooked, the contents of free and bound phenolics changed, and the latter was relatively stable, indicating that it may play a more important role in the body.

Key words: millet; millet porridge; polyphenols; antioxidant activity; metabolomics