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Flaxseed is one of the world’s major oilseed crops. Defatted flaxseed meal has a high protein content and favorable nutrition profile. However, it is currently mainly used as animal feed or fertilizer. Limited research has been done on isolation, physicochemical or functional properties of flaxseed protein constituents. These studies are necessary to realize the potential use of flaxseed proteins as food ingredients.

The objective of our study was to establish a protocol for isolation of major storage proteins from flaxseed.

Dehulled NorMan flaxseeds were ground, delipidated with methanol-chloroform, then extracted with 0.10 M NaCl in 0.10 M Tris at pH 8.6. The supernatant obtained by centrifugation of the extract was fractionated by DEAE-Sephacel chromatography with step gradient elution from 0.10 M to 0.50 M NaCl. All fractions were monitored for conductivity and A₂₈₀ . Pooled fractions were freeze-dried, desalted by dialysis and analyzed by electrophoresis. Protein content was estimated from nitrogen determined by a combustion method.

Protein contents of dehulled and dehulled delipidated flaxseeds were 27.3% and 52.6%, respectively. The elution profile from DEAE chromatography showed that proteins eluted by 0.20 M NaCl accounted for the major fraction. SDS-PAGE showed mostly low molecular weight bands for the unbound fraction in 25 mM Tris buffer and the fraction eluted at 0.10 M NaCl; these fractions may correspond to a 2S protein reported in the literature. Fractions eluted at 0.15, 0.20 and 0.25 M NaCl had very similar electrophoretic profiles, consisting of six bands on non-reducing SDS-PAGE with molecular weight ranging from 11 to 50 kD, similar to values reported in the literature for the major storage 12S protein.

The isolation procedure successfully fractionated high and low molecular weight major storage proteins of flaxseed and can serve as a base for further investigation of the structural and functional properties of these proteins.