Flaxseed is the seed of flax, which is widely planted in my country as an oil crop. Extracting protein from the cake after oil extraction can greatly improve the overall availability of flaxseed. Studies have shown that flaxseed protein and its polypeptides have various physiological functions such as inhibition of angiotensin-converting enzyme activity, antibacterial, anti-diabetic, etc., and have great development potential and research value, but they have not yet been commercialized. Ripe flaxseeds are flattened oblong and consist of two cotyledons surrounded by a thin endosperm and a smooth seed coat. The shell of flaxseed mainly contains flax gum, lignans, dietary fiber and cyanogenic glycosides; flaxseed mainly contains flax oil and flax protein. The shells and kernels of flaxseeds are separated, and the cake meal after oil extraction from flaxseeds is used to extract protein, which not only improves the protein extraction rate, but also achieves the purpose of detoxification; extracting flaxseed gum, lignans and Dietary fiber, so that the comprehensive development and utilization of flaxseed can move towards a benign track of high efficiency and low consumption. There are some physical or chemical methods for the separation of husk kernels, and flax kernels are relatively easy to obtain.

There are various extraction methods for flaxseed protein, including desalination and precipitation, alkali extraction and acid precipitation, and ultrasonication. Currently, alkali extraction and acid precipitation is widely used at home and abroad. Compared with other methods, this method can achieve repeated extraction. Tirgar et al. found that the surface hydrophobicity and emulsifying ability of flaxseed protein extracted by alkali extraction and acid precipitation were significantly higher than those by enzyme method and enzyme solvent extraction method; Kaushik et al. , the flaxseed protein obtained by this method has extremely high purity and good thermal stability, and the solubility in pH 9.0 buffer can reach 76%, and the formed emulsion has high acid stability; Kong Huiguang et al. Using cold-pressed flaxseed meal as raw material, the protein was also extracted by alkali extraction and acid precipitation, and the flaxseed protein was dried by freeze-drying and spray-drying. Xu Guangying et al. used dehulled flaxseeds as raw materials to extract proteins by alkali extraction and acid precipitation, but they only determined the optimal process conditions through orthogonal experiments, and did not systematically analyze and evaluate the properties of the extracted proteins.

Based on the above research background, this research uses flaxseed as raw material, removes linseed oil by mechanical cold pressing combined with organic solvent extraction method, and then extracts flax protein by alkaline extraction and acid precipitation method; The content, solubility, molecular weight, water-holding capacity, oil-holding capacity, emulsifiability and amino acid composition of each protein component were analyzed and detected, and the potential active polypeptide sequence was analyzed by the online enzymatic hydrolysis website. The research results will provide a reference for the efficient utilization of flax protein, and provide data support for the future development and application of flax protein and its active peptides.