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Effect of roasting on phenolics content and antioxidant activity of proso millet
F. HAN (1), L. Zheng (2), W. Di (1), Y. Liang (1), X. Chen (1), A. Li (1). (1) Academy of State Administration of Grain, P.R.China, Beijing, China; (2) School of Food Science and Technology, Jiangnan University, Wuxi, China

The influence of roasting on the antioxidant activity and phenolics content of two varieties of proso millet (<i>Panicum miliaceum</i> L.) was studied. Changes of phenolic and flavonoid contents and the antioxidant properties during the roasting of soaked proso millet seeds at 180ºC were measured by the DPPH, ABTS, FRAP and ORAC assays. These contents and properties increased markedly after roasting for 10 min. After 30 min, the total content of phenolics and flavonoids was increased 1.6-fold and 1.2-fold, respectively, for the Nei Mei 8 variety and 1.6-fold and 1.3-fold, respectively, for the Xi Nong 10-4 variety of <i>P.</i> <i>miliaceum.</i> The antioxidant capacity was increased significantly (<i>p </i><0.05). The positive correlation coefficients between the total content of phenolics, total content of flavonoids and antioxidant activity were high; the highest was between total content of phenolics and FRAP (<i>r</i> 0.995). Nine individual phenolic compounds were identified in roasted proso millet. The predominant phenolic acids were <i>p</i>-coumaric acid and <i>trans</i>-ferulic acid in the free fraction and vanilic acid, <i>p</i>-coumaric acid and <i>trans</i>-ferulic acid in the bound fraction. The most abundant phenolic acid in proso millet was <i>trans</i>-ferulic acid. This study showed that roasting increased the content of phenolic compounds and the antioxidant activity of proso millet.

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