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This study compared the effectiveness of urea-containing and urea-free L-cysteine solutions in extracting high-quality feather keratin and evaluated commercial proteases for producing keratin-derived bioactive peptides. The urea-assisted extraction was crucial for achieving high structural integrity and yield of soluble keratin. The keratin isolate exhibited oil-holding capacity of 9.37 g/g, foaming capacity of up to 127 %, and emulsifying capacity of up to 49 %. Its proteolysis with trypsin, chymotrypsin, pepsin and subtilisin resulted in peptides with average molecular weight between 2.10 and 5.96 kDa and degree of hydrolysis from 6 to 36 %. The subtilisin hydrolysate had the highest degree of hydrolysis, 63 % of peptides <1 kDa, and excellent solubility across a wide pH range, but negligible water and oil-binding, foaming, and emulsifying properties. This study highlights the need to optimize each step in keratin extraction and hydrolysis processes to produce high-quality bioactive keratin preparations for diverse applications, including food and pharmaceutical. • Urea-assisted extraction with L-cysteine enhances yield and quality of keratein. • Keratin isolate shows great gelling, oil-binding, foaming and emulsifying properties. • Proteolysis enhances solubility but impairs gelling and oil-binding of keratein. • Foaming and emulsifying properties of keratin hydrolysates are DH and pH-dependent.
Taraszkiewicz et al. (Tue,) studied this question.