Synthesis and Surface Properties of Amino Acid Surfactants from Industrial Waste Proteins

N -Acyl amino acid surfactants (AAS) were chemically derived from industrial waste protein hydrolysates [cottonseed (CSD), silk residue (SR), and silk chrysalis (SC)] according to two methods: (1) reacting hydrolysates with alkyl acyl chloride, followed by purification and neutralization with alcoholic sodium hydroxide; (2) reacting hydrolysate with fatty alcohols in organic solvents followed by purification. The yield of purified mixed AAS (sodium salt) was ∼60−75%; amino acid ester from glutamic acid was considerably higher (85−92%) than the sodium salt derivatives. Results indicate that as acyl chain length (i.e., C 12 −C 18 ) increased, surface tension of AAS increased, critical micelle concentration (cmc) decreased, and Krafft point increased. The emulsifying power of AAS in O/W emulsion was better with n -decanol as an oil phase than liquid paraffin. The C 12 derivatives of all the mixed AAS showed high foaming power. Mixed AAS from CSD exhibited the best lime soap dispersing requirement (5.7−6.5 g/100 g). The diameter of micelle increased for glutamic acid AAS (GA-AAS) and CSD-AAS as the acyl chain length increased (i.e, C 12 −C 18 ). The hydrodynamic diameter of AAS followed the order SC > CSD > GA. Generally, AAS with C 12 produced good surface properties.