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Two branched canola protein isolates (CPI) with different branching degree were prepared using bis-epoxide as a chain extender. It was found that the branching reaction may take place in any protein fraction in native CPI; furthermore, by increasing the amount of chain extender, more native protein chains in CPI were coupled to form branches. In the study of flow properties of native and branched CPI solutions, it was found that the apparent viscosities of two branched CPI remarkably increased compared to that of native CPI over all concentrations tested. At 22 °C and pH 7, native CPI solution showed slight shear thinning behavior with the increase of shear rate; however, shear thickening was observed at low shear rate for branched CPI. Furthermore, shear thickening was more pronounced with the increase of branching degree and concentration of branched CPI solution. Shear thinning behavior of native CPI became marked at pH 11; however, the shear thickening property of branched sample was weakened at high pH. The novel findings in flow properties of the branched CPI solution could be potentially applied in the food industry, such as increasing foaming property and gelling ability of food products. [ABSTRACT FROM AUTHOR]

Cross-linked canola protein isolate (CPI) films were prepared using a bisepoxide as a chain extender by wet cast followed by heat compression. By DSC measurements, it was verified that the cross-linking reaction took place in the CPI matrix and was completed in 10 min at 90 °C. FTIR analysis confirmed that the chain extenders were covalently bonded with CPI chains. The reaction led to the formation of a cross-linked architecture which was revealed by an increase in molecular weight of the modified CPI films. The newly formed chain architecture increased the thermostability of CPI as evaluated by TGA; furthermore, the thermostability increased with the increase in cross-linking degree of the modified CPI films. DMA results of the unmodified CPI film showed that microcosmic phase separation occurred between two major proteins, cruciferin and napin in CPI; however, the extent of phase separation decreased with the increase of chain extenders and finally disappeared because of the increased compatibility between cruciferin and napin. Elastomeric mechanical behavior was observed with the introduction of cross-linked architecture in the modified CPI films. At low humidity of 55%, the cross-linked CPI films showed an increase in tensile strength and a decrease in elongation at break. At high humidity of 98%, the increase in hydrophobicity of cross-linked CPI matrix resisted the decreasing tensile strength seen in unmodified films. [ABSTRACT FROM AUTHOR]