Effect of Acylation on Flax Protein Functionality

Flaxseed meal contains 34 to 37% protein on a dry weight basis. Proteins of the meal could be isolated by complexation with sodium hexametaphosphate; the yield of the protein isolated could be improved upon prior removal of mucilage from flaxseed. The protein isolate so prepared was acylated with acetic or succinic anhydride in order to improve its functional properties. The degree of acylation of free amino groups was progressively increased with increasing anhydride concentration, however, a lower degree of acylation was achieved when succinic anhydride was used in place of acetic anhydride. The color of the acylated proteins became lighter as the degree of acylation was increased. Both acetylation and succinylation increased solubility of the isolate at all levels of acylation examined. Emulsification properties of protein preparations were improved due to acylation, particularly for succinylated products. The foaming properties of flax protein isolates were not improved by acylation. Low degrees of acetylation improved fat binding capacity of flax protein isolates, but succinylation did not render such an effect. Acylation also increased surface hydrophobicity of the products and the highest value was observed at the lowest degree of acetylation.