No, keratin is not soluble in water. This is a consistent finding across numerous scientific sources.
Keratin's Insolubility in Water
Several sources confirm keratin's insolubility in both cold and hot water. This insolubility is a key characteristic of this fibrous structural protein. The strong disulfide bonds within the keratin structure contribute significantly to its resistance to water and other solvents. Britannica describes keratin as being "completely insoluble in cold or hot water". Similarly, Cleveland Clinic states that keratin's strength prevents it from dissolving in "diluted acids, alkalines, solvents or waters". Further support comes from Wikipedia which highlights keratin's "extreme insolubility in water and organic solvents". And ScienceDirect mentions that native keratin is not water-soluble.
Soluble Keratin: A Note on Modification
While native keratin is insoluble, it's important to note that modified keratin can be made water-soluble. This often involves chemical processes like hydrolysis, which breaks down the keratin structure. Goonvean Fibres explains that keratin is chemically modified to achieve water solubility using an alkaline process. This modified, soluble keratin is different from the naturally occurring, insoluble form. The reference to soluble keratin on Quora (Quora) is likely referencing this modified form. The Reddit discussion on hydrolyzed keratin also points to this distinction. The process of making keratin water-soluble will destroy its original structure.
Practical Implications
The insolubility of keratin explains why it's a crucial component of strong structures like hair, nails, and skin. Its resistance to water and enzymes is essential for its protective and structural roles.
