Progress in Keratin Extraction Methods and Suggestions on Selection of Extraction Techniques for Application

Keratin is a kind of renewable protein with high cystine content, stable structure and appropriate biological performance, which mostly exists in animal hair. This paper briefly introduced the structure and properties of keratin at first, and then summarized in detail the extraction technologies of keratin such as acid-base method, reduction method, oxidation method, enzymatic hydrolysis method, and ionic liquid assisted-, metal salt assisted-, and copper ammonia solution assisted method. The aspects of principle, conditions, extraction yield, keratin molecular weight, application status, etc., have been formed. The advantages and disadvantages of various methods, the molecular weight, sulfhydryl content and other characteristics of the extracted keratin and its potential application direction also have been compared and discussed. Finally, the development trend of keratin extraction technology and how to select suitable extraction technology according to the needs of application fields are prospected.