Flaxseed (Linum usitatissimum L.) is an oilseed used in industrial and natural health products. Flaxseed accumulates many biologically active compounds and elements including linolenic acid, linoleic acid, lignans, cyclic peptides, polysaccharides, alkaloids, cyanogenic glycosides, and cadmium. Most biological and clinical studies of flaxseed have focused on extracts containing α-linolenic acid or lignan. Other flaxseed compounds have received less attention and their activity is not well described. The benefits of consumption of whole flaxseed fractions such as oil, mucilage and protein indicate that consideration of the entire portfolio of bioactives present is required to associate biological activity with specific compounds.

Flaxseed ( Linum usitatissimum L.) bioactive compounds and peptide nomenclature: A review

Flaxseed proteins—a review

Isolation and structural characterization of the major protein fraction from NorMan flaxseed (Linum usitatissimum L.)

Summary
Flaxseed proteins are potent multi-functional ingredients for food formulation owing to their techno-functionalities, food preservation capacity, and health benefits. A possible synergistic effect with mucilage on their functionalities could be valuable even though this co-product in flaxseed may limit the protein yield during their production processes. Their techno-functional properties could also be considered in mixture with other flax bioactive components such as lignans and fibre to enhance the value of the flaxseed meal. The present paper reviews flaxseed protein uses in food and their health benefits. New perspectives according to consumers’ demand for products with health promoting bioactive components are also suggested.

Flaxseed proteins: food uses and health benefits

Six laboratory-prepared (LM) and four commercially-obtained (CM) samples of linseed meal were analyzed for eleven proximate components, ten mineral elements, monosaccharides, amino acids, and seven vitamins (two samples only). Analysis of variance of LM data showed location had a greater influence on meal composition than did cultivar. LM and CM had similar composition, except for protein, total carbohydrates, acid-detergent fiber and lignin. Hull separated by a liquid cyclone process formed 37.5% of the seed and contained less than 1% oil, 20% protein and 32.9% total monosaccharides. Xylose and arabinose were the major sugars. Meal absorbed 8-fold, and the hull 13-fold their weights of water (water-hydration capacity), compared to less than 2-fold by similar fractions of canola (rapeseed) and soybean. Viscosities of aqueous extrats of hull were stable for 30 min at 25°C, and were concentration-dependent.

Compositional analysis of laboratory-prepared and commercial samples of linseed meal and of hull isolated from flax.

Defatted linseed flour was prepared from cold-pressed seed meal via hexane extraction of the residual oil, followed by removal of the major portion of the hulls through grinding and sieving (sieve size 0.25 mm). The resulting flour had 50% protein on a dry basis compared with 40% contained by the whole seed on an oil-free dry basis. Nitrogen extractability of the defatted flour in water was not influenced by the length of the extraction period but an increased extraction was observed at higher solid:liquid ratios up to the studied limit of 1:40. The smallest amount of nitrogen (20%) was extracted in the pH range 4.0–4.6 and the greatest (80%) at pH 12.0. Addition of NaCl (0.1–1.0 M) broadened the pH range of minimum nitrogen extractability and shifted it towards lower pH region. At higher concentrations (0.6 and 1.0 M) NaCl markedly increased nitrogen extractability in the pH range of 4.0 to 8.0. Precipitation of protein from an extract at pH 10.0 was maximum (77%) at pH 4.1. A higher buffer capacity of the flour was observed in the acidic medium (0.204 mmol HCl g−1 flour) than in the alkaline medium (0.096 mmol NaOH g−1 flour).

Erika Quensel

Papers

Nitrogen extractability and buffer capacity of defatted linseed (Linum usitatissimum L.) flour

Verfahren zur herstellung eines proteinerzeugnisses