Systematic studies on the solubility of feather keratin in the ureawater system, serving for the optimization of composition of keratinurea granulates, were carried out. The dependence of keratin solubilization on the concentration of urea and time of heating was examined. From the amino acid compositions determined it may be assumed that solubilization of keratin results from the break of disulphide bridges. The quantitative amino acid composition of keratin urea granulates reveals negligible changes in relation to feather keratin what may be an evidence that the technological process of production of granulates does not cause any losses.
A method of solving chicken feather keratin proteins in dimethylsulphoxide (DMSO) was developed. Two fractions of modified keratin were obtained: one which dissolves in DMSO, that is precipitated after acetone is added, and another one which does not dissolve in DMSO. The soluble fraction contains 90.5% protein. This protein contains approximately 7% of sulphuric amino acids and its real digestibility is 76.7. The method described in this paper is a continuous dissolving method which also encures the circulation of solvents in a closed circuit.