Properties of Canola Protein-based Plastics and Protein Isolates Modified Using SDS and SDBS

Canola protein isolates were prepared from canola meal flour using alkaline solubilization and acid precipitation. The isolates were treated with sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) with concentrations between 1 and 5%. Functional property analysis of modified isolates revealed that water absorption and fat absorption increased by up to 115 and 78%, respectively, with increasing SDBS concentrations. Fat absorption of SDS-modified isolates showed a similar trend to that of SDBS-modified isolates (86% increase), but water absorption decreased (by 77%) in the 5% SDS treatment. SDS and SDBS treatments reduced the emulsifying activity of protein isolates by 34 and 30%, respectively. The denaturation effect of SDS and SDBS treatments increased the surface hydrophobicity of proteins and resulted in increased tensile strength (by 14 and 41%), tensile modulus (by 31 and 52%), and toughness (by 44 and 64%) of plastic specimens prepared using modified isolates. Only the 3% treatments of SDS and SDBS increased the elongation of plastics (by 22 and 11%, respectively) while other treatments did not show significant differences from the plastics that used non-modified isolates. The water absorption of plastics increased by 33% with the 5% SDS treatment; the SDBS treatments showed a 9% decrease in water absorption for the 1% treatment but no significant differences at higher concentrations. Denaturation by SDS and SDBS can be employed to alter functional properties of canola protein isolates as well as the mechanical properties of canola protein-based plastics.