Blends of cysteine-containing proteins.

Proteins such as keratin, lactalbumin, and gluten can be obtained from agricultural sources. These proteins contain the amino acid cysteine. Cysteine allows for the formation of inter- and intramolecular sulfur-sulfur bonds. It was found that cysteine-containing proteins have varied properties and can be blended together to form materials with the attributes of each polymer. The addition of wheat gluten to other proteins increases the strain to break or "toughness". The addition of lactalbumin increases the modulus and strength of blends. Birefringence shows that lactalbumin contains an added "structure" not found in the other proteins. Permeability studies reveal that one protein may dominate the transport of small molecules through the blend. Scanning electron microscopy shows that blends contain features of each protein and correlate with observed tensile properties.