Abstract: The extraction of protein from Allium cepa L. var. agrogatum Don by alkali dissolution and acid precipitation was optimized using orthogonal array design method. Along with this, the extracted protein was also characterized. The results showed that the maximum extraction efficiency of protein of 79.38% was obtained after extraction at 50 ℃ and pH 9.0 with a solid-to-solvent ratio of 1:15 (g/mL) for 1.5 h. HPLC analysis demonstrated that the protein consisted of 38.96% essential amino acids and 61.04% non-essential amino acids. Electrophoresis showed that the protein was composed of four components with molecular weights of 61.94, 27.10, 17.62, and 13.34 kDa. The secondary structure consisted of 52.60% α-helix, 8.60% β-sheet, 15.60% β-turn and 22.40% random coil. The characteristic functional groups of the protein were confirmed by infrared spectroscopy.

Key words: Allium cepa L. var. agrogatum Don, protein, orthogonal array design, characteristics