Abstract
Flaxseeds (Linum usitatissimum L.) are oilseeds endowed with nutritional constituents such as lignans, lipids, proteins, fibre, carbohydrates, and micronutrients. Owing to their established high nutritional profile, flaxseeds have gained an established reputation as a dietary source of high value functional ingredients. Through the application of varied bioprocessing techniques, these essential constituents in flaxseeds can be made bioavailable for different applications such as nutraceuticals, cosmetics, and food industry. However, despite their food and health applications, flaxseeds contain high levels of phytotoxic compounds such as linatine, phytic acids, protease inhibitors, and cyanogenic glycosides. Epidemiological studies have shown that the consumption of these compounds can lead to poor bioavailability of essential nutrients and/or health complications. As such, these components must be removed or inactivated to physiologically undetectable limits to render flaxseeds safe for consumption. Herein, critical description of the types, characteristics, and bioprocessing of functional ingredients in flaxseed is presented.
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Key Findings
In this review, the functional/bioactive ingredients derived from flaxseed and the processing techniques used for extraction or isolation of these ingredient is described. The authors note that flaxseed is a nutrient-and functional food ingredient-rich seed with high levels of vitamins, minerals, proteins, lipids, dietary fibre and lignans. ‘Green’ approaches for the extraction and purification of the many functional food ingredients obtainable from flaxseed are needed. The suitability of extraction procedure and isolation techniques depend on the type of the nutrient, the scale of isolation, and commercialization feasibility. For isolation of carbohydrates from flaxseeds, solid-liquid extraction may be used for reasonably high yields and low costs. However, super/subcritical fluid extraction strategies have garnered considerable attention due to their assorted range of benefits such as renewability and sustainability, varied range of polarities, higher selectivity, which are all suitable for derivation of food-quality extracts. For extraction of proteins from flaxseeds, both conventional and novel strategies have been tried. In spite of certain demerits, isoelectric precipitation is still the most prevalent traditional method for protein isolation, mainly because of the associated high yield. Novel techniques such as ultrasound-assisted extraction, electro-activation and pressurized low-polarity water extraction also hold promise, but these have to be optimized to improve their performance and overcome the associated high maintenance costs. For lipid extraction, aqueous extraction with nitrogen protection has emerged to be a technique of interest, considering its extremely high production yield. Although linked with high costs, sub/supercritical fluid extraction of lipids remains a high value technique because of the high quality of the extract, amenability to environment, scalability and commercial feasibility.