Canola meal fractionation and utilization for protein-based thermoplastics.

摘要

Albumins, globulins, prolamins, and glutelins were separated from canola meal flour using the classical Osborn method. A modified method was developed and tested resulting in better separation of protein fractions with a 59% increase in globulin yield and a 57% decrease in albumin yield. Canola flour produced by cold-milling (compared to traditional screw-pressing) resulted in a 20% increase in protein yield and altered functional properties. The milling temperature impacted protein quality and yield.Canola protein isolates were used to prepare injection-molded plastic specimens. Four plasticizers were tested and all improved water resistance (by 31--36%) of the protein-based plastics. Glycerol-plasticized specimens showed greatest improvements in tensile strength, elongation, and toughness by 51%, 173%, and 277%, respectively. The specimens plasticized by polyvinyl-alcohol showed greatest improvements in flexural strength (by 83%) and modulus (by 171%). Fracture morphology analysis revealed ductile-type failure in plasticized specimens and brittle-type failure in unplasticized specimens.Canola proteins were also classified according to their isoelectric points ranging from pH 11 to 3. The pH-11 fraction showed highest water absorption and lowest melting point. Plastics prepared with refined protein isolates (pH-11 fraction removed) showed improvements in elongation, water resistance, tensile strength, flexural strength, and toughness (by 35, 11, 16, 12, and 62% respectively) compared to plastics prepared with standard protein isolates.A central composite design was used to quantify the effects of protein extraction conditions on protein quality and plastic properties. The highest functional and mechanical properties occurred towards high and low ends of solubilization pH values respectively, but precipitation pH did not show clear trends. When optimizing for tensile strength, toughness, and elongation those values can increase by 160%, 270% and 930%, respectively, over what is seen at maximum yield conditions these gains can be achieved with less than a 6% reduction in yield.Protein modification via sodium dodecyl-sulfate (SDS) and sodium dodecyl-benzene-sulfonate (SDBS) were shown to increase the toughness, tensile strength, and modulus of plastic specimens by up to 64, 41, and 52% respectively over those prepared with standard isolates. Elongation and water resistance, however, were generally insensitive to the SDS and SDBS modification.