Abstract: Although cold-pressed flaxseed meal is rich in protein, it is mainly used as animal feed or discarded, resulting in a serious waste of resource. In this study, protein was extracted from flaxseed meal by alkali dissolution followed by acid precipitation, and its physical properties and nutritional value were evaluated. The results demonstrated that the protein content of the extract was as high as 98.86%. Sodium dodecyl sulfate-polyacrylamide gel?electrophoresis?(SDS-PAGE) analysis showed the darkest bands at 21 and 33 kDa. A total of 11 flaxseed proteins reported in the literature were identified in the protein by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the isoelectric point (pI) of the protein was located around at pH 4.0. A total of 17 amino acids including many essential ones were detected in the protein using an automatic amino acid analyzer. The oil-binding capacity of the protein was more than five times as large as its water-holding capacity. Moreover, the protein exhibited high emulsification activity, but its emulsion stability was slightly poor. The stability of the secondary structure was moderate, but it had good thermal stability.

Key words: flaxseed protein; alkali extraction-acid precipitation; physical properties; nutritional value