Effect of pressure treatment on hydrophobicity and SH groups interactions of myofibrillar proteins

Response surface methodology was used to study the simultaneous effect of two independent variables : Pressure [0 - 600 MPa] and Time [0 - 1800 s] according to a central composite design in stars. The significant responses were the surface hydrophobicity, the ratio -SHfree / SHtotal and the flowing properties. Surface hydrophobicity was determined using 1-anilinonaphtalene-8 sulfonate (ANS) as hydrophobic fluorescence probe. The ratio -SHfree / SHtotal was determined using the 5-5'-Dithiobis-2-nitrobenzoic acid. Flowing properties (flow index and viscosity coefficient) of solutions were stemmed from modelised flow curves performed with a rheometer AR1000. Results show that high pressure treatment induces an increase of the surface hydrophobicity of myofibrillar proteins (x 3) from 0 MPa to 440 MPa, and from 450 MPa to 600 MPa the surface hydrophobicity is stable. The same trend are obtained with the sulfhydryl interactions and the rheological index n. The viscosity coefficient K decreases with the increase of pressure : the viscosity decreases in relation to a change of structure of the proteins. The statistical analysis of responses show that the most important significant effects are the pressure and its quadratic effect compared with the effect of time.