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Aroma Stability of Millet Powder During Storage and Effects of Cooking Methods and Antioxidant Treatment

¹College of Food Science of Nutritional Engineering, China Agricultural University, Beijing, China, 100083. ²Ruican Wang and Yijing Chen contributed equally to this work. ³Corresponding author. Box 303, China Agricultural University, No. 17 Qinghua Donglu Haidian District, Beijing, China, 100083. Phone: +86-10-62737634. E-mail: Shuntang@cau.edu.cn

Foxtail millet is a cereal crop that contains high levels of unsaturated fatty acids, so that processed food such as instant millet powder is susceptible to lipid oxidation, which gradually leads to deteriorated flavor and quality. In this work, volatiles of millet powder samples with or without storage at room temperature for 12 months were extracted and analyzed by gas chromatography–olfactometry/mass spectrometry. In fresh steamed millet powder, hexanal, 2-pentylfuran, and 3-octen-2-one might be dominant odorants, whereas in deteriorated steamed millet powder, volatiles such as 1-octen-3-ol, (E)-2-octen-1-ol, (E)-2-octenal, 3-nonen-2-one, (E)-2-nonenal, decanal, 2-undecanone, and 2-methylnaphthalene emerged or increased over time, among which 1-octen-3-ol and (E)-2-nonenal were highly responsible for its rancid flavor. We also compared millet powder prepared with two different processing methods, steaming and extrusion. Compared with steaming, extrusion was a cooking method of millet that helped slow the generation of oxidized flavor to some extent. When 0.04 g/kg (w/w millet) of ascorbyl palmitate was added as an antioxidant before drying, the production of unpleasant odorants was significantly inhibited, so that the quality of final products was improved. Analysis of odorants can be an alternative method for evaluating the storage stability of processed food.