Elastic properties of protein gels obtained by three-phase partitioning

Abstract

A special combination of alcoholic precipitation and salting out of proteins was described as three-phase partitioning [1]. Proteins are accumulated in a coherent middle phase in the partitioning system composed of tert-butanol, ammonium sulphate and water. The mechanical properties of the middle phase were determined in model systems using bovine serum albumin (BSA) or ovalbumin. The stressdeformation relationship obtained by uniaxial compression showed the elastic behaviour of the middle phase. It was found that the elastic modulus of the protein gel changed with stress. The middle phase became harder upon compression, possibly owing to some change in structure. The viscoelastic properties were determined by measuring the deformation as a function of time. The BSA gels showed higher elastic and viscous deformation and lower viscosity than the ovalbumin gels. The rheological behaviour of protein gels is consistent with the previous results obtained from the analysis of middle-phase components, which indicate that the middle phase formed in three-phase partitioning is an emulsion gel.