Physicochemical Properties and Antioxidant Activity of Non-waxy and Waxy Proso Millet (Panicum miliaceum L.) Subjected to Electron Beam Irradiation

To investigate the effects of electron beam irradiation on the physicochemical properties and antioxidant activity of non-waxy and waxy proso millet.

waxy (‘Yushu 1’) and non-waxy (‘Yumi 2’) proso millet were subjected to electron beam irradiation at different doses of 0 (control), 2, 4, 6, 8, and 10 kGy and were evaluated for physicochemical properties, bioactive substances and antioxidant capacity.

After electron beam irradiation, the color, starch content, ash content, phenolic content and antioxidant activity of non-waxy and waxy proso millet changed significantly (P < 0.05), while the physical properties, moisture content and protein content did not (P > 0.05). In addition, electron beam irradiation treatment significantly increased the contents of total phenols and total flavonoids, antioxidant activity and individual phenolic contents in non-waxy and waxy proso millet; the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity increased up to 78.01% and 70.22%, and the 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging capacity increased up to 61.51% and 50.57%, respectively. The contents of gallic acid, caffeic acid, resveratrol, catechin and kaempferol in proso millet extract increased, while the contents of protocatechuic acid and epicatechin remained relatively stable. The correlation analysis suggested that the total phenolic content had a significantly positive correlation with the contents of catechin and quercetin (P < 0.01), the total flavonoid content had a significantly positive correlation with the contents of rutin and gallic acid (P < 0.01), and the antioxidant activity was positively correlated with the catechin content. Compared with the control, proso millet treated with electron beam irradiation exhibited stronger antioxidant properties and higher phenolic contents, which would be worthy of further research and development.