Flaxseed: A Powerful Food Ingredient

Abstract: Flax (Linum usitatissimum) has been used for centuries as a source for oil extraction. In recent years it has attracted considerable interest as a result of studies that attribute potential health benefits to its components, including the prevention of chronic non-communicable diseases. Among these compounds presenting biological activity, alphalinolenic acid, lignans, and soluble fiber are of special interest.

The purpose of this article is to understand and explore the valuable nutritional and therapeutic properties of flaxseed for domestic and industrial use. This understanding will be an excellent opportunity to reintroduce this powerful food ingredient to the world.

Introduction:

Flaxseed, or Linseed (Linum Usitatissimmum), popularly known as Alsi, Jawas, Aksebija in Indian languages, is a blue flowering rabi crop and a member of the family Linaceae. Globally, Flaxseed is grown as either an oil crop or a fiber crop with fiber linen derived from the stem of fiber varieties and oil from the seed of linseed varieties. The plant is native to West Asia and the Mediterranean. As the source of linen fiber flax has been cultivated since at least 5000 BC, today it is mainly grown for its oil. The spherical fruit capsules contain two seeds in each of five compartments. The seed is flat and oval with a pointed tip. It has a smooth glossy surface. It varies in color dark brown to yellow.

It is the third largest natural fiber crop and one of the five major oil crops in the world. The texture of flaxseed is crisp and chewy possessing a pleasant nutty taste. Beyond its oilseed crop ability, proximate composition of flaxseed makes it more promising for its utilization in different food products. Flaxseed is one of the richest vegetarian source of α- linolenic acid (omega 3 fatty acid) and soluble mucilage. In present era, consumer’s trend towards functional food has increased significantly as health awareness rose. Flaxseed can be one stop for novel high quality source of nutrition.

History:

Flax (Linum usitassimum) has a long history of use as a food, medicine, and textile fibre. The Latin name means “very useful”. Hippocrates used flax to treat abdominal pain. Originally cultivated in Mesopotamia, the use of flax has been documented as far back as 3000 BC. This Flax differs in genera from the native New Zealand flax (Phormium tenax and Phormium cookianum) which was given the common name “flax” by settlers in reference to its use as a source of fibre for weaving. The seeds from the two genera differ markedly in their appearance, chemical composition, and use.

Flaxseed (Linseed) encompasses the potential health suiting nutritional profile in it. However, many people are still unaware of the potential health benefits of flaxseed and food applications. ALA (omega-3 fatty acid), dietary fiber and Lignan (specifically SDG) content attracts food technologists to explore its abilities at fullest extent in commercial food processing sector. Recently Baking and Pasta companies have incorporated flaxseed into their formulations. General recommendation for daily intake has been 1–3 table spoons per day for ground flaxseed or 1 table spoon for flaxseed oil. Flaxseed is emerging as one of the nutritive and functional ingredient in food products.

Flax is rich in fat, protein and dietary fibre.

The composition of flaxseed is shown in Table 1.

Table No. 1: Composition of Flaxseed.

Source of Omega-3 Fatty Acid:

There are two groups of omega fats: omega-3 and omega-6 fatty acids. Linolenic acid, eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) are three types of omega-3 fatty acids and are nutritionally important. All three fatty acids have been shown to reduce the risk of cardiovascular disease. Flax contains a mixture of fatty acids. It is rich in polyunsaturated fatty acids, particularly ALA, the essential omega-3 fatty acid, and linoleic acid (LA), the essential omega-6 fatty acid. These two polyunsaturated fatty acids are essential for humans – that is, the body needs them.

Fatty acid content of flaxseed oil is shown in Table 2.

Table No. 2: Fatty acid content of flaxseed oil

ALA and Linoleic acid constitutes 57% and 16.0 % of total fatty acids respectively in flax making the richest source of ALA. ALA from flaxseed exerts positive effect on blood lipids. It was found to be as effective as oleic acid (18:2η-6) and linoleic acid (18:2η-6) in the reduction of plasma total cholesterol, low density lipoprotein cholesterol and very low density lipoprotein cholesterol. ALA, being the essential fatty acid, requirement can be fulfilled by intake of flaxseed products.

Source of Protein:

The protein content in flaxseed has been reported to between 10.5% and 31%. Albumin and globulin type proteins are the major proteins in flaxseed. Flaxseed albumin comprised 20% of meal protein. Globulin fraction makes up to 73.4% and the albumin constitutes about 26.6% of total protein. Flaxseed proteins are relatively high in arginine, aspartic acid and glutamic acid whereas lysine, methionine and cystine are limiting amino acid.

The biological value BV of flaxseed protein was similar to those of soybean protein. Flaxseed protein was effective in lowering plasma cholesterol and triglycerides (TAG) compared to soy protein and casein protein.

Source of Dietary Fiber (Mucilage or Gum):

Dietary fiber is a communal word used to describe a variety of plant substances that are not easily digested by the enzymes responsible for digestion in humans. Diets rich in dietary fibre may help reduce the risk of heart disease, diabetes, colorectal cancer, obesity and inflammation. Flaxseed is a rich source of dietary fiber (accounting 28% shown in Table 1), both soluble as well as insoluble fibers.

Total dietary fiber content of flaxseed is given in Table 3.

Table No. 3: Total dietary fiber content of flaxseed.

The high amount of dietary fiber adds bulk to waste products in the gut and increases bile movement in the gastrointestinal movement. It exhibits the natural laxative effect of dietary fiber. Flaxseed mucilage associated with the hull of flaxseed is a gum-like material composed of acidic and neutral polysaccharides. The neutral fraction of flaxseed contains xylose (62.8%) whereas the acidic fraction of flaxseed is comprised mainly of rhamnose (54.5%) followed by galactose (23.4%).

Low glycemic index foods containing soluble fiber not only prevent certain metabolic ramifications of insulin resistance but also reduce insulin resistance. Soluble fiber and other components of the flaxseed fraction could potentially affect insulin secretion and its mechanism of action in maintaining plasma glucose homeostasis.

Source of Lignan (Phenolic Compounds)

Flaxseed is the richest source of plant lignans. Secoisolariciresinol diglucoside (SDG) is the predominant lignan in flaxseed with minor amount of pinoresinol and matairesinol (MAT). SDG was found 2653 mg/100 g of nondefatted flaxseed extract. lignans of flaxseed are phytoestrogens and serve as precursors in the production of mammalian lignans. Flaxseed lignans convert to mammalian lignans enterolactone and enterodiol by intestinal flora. Enterolactone and enterodiol had greater antioxidant activity than the present lignan (SDG), suggesting that the metabolites might be the reason for the health benefits of plant lignans. Lignans have antioxidant activity and thus may contribute to the anticancer activity of flaxseed. Flaxseed, in particular, lignans could influence bone development.

Vitamins and Minerals:

Flaxseed contains a good amount of water and fat-soluble vitamins. Vitamin E is present abundantly in flax primarily as gamma-tocopherol. Gamma-tocopherol is an antioxidant that protects cell proteins and fats from oxidation; promotes sodium excretion in the urine, which may help lower blood pressure; and helps lower the risk of heart disease, some types of cancer, and Alzheimer disease.

The tocopherol content of flax is affected by the variety, maturity of the seed, growing region, growing conditions, and method of extraction. The gamma-tocopherol content can range from 8.5 to 39.5 mg/100 g of seed or about 0.7- 3.2 mg/tbsp of milled flax. Flax contains a small amount of vitamin K in the form of phylloquinone, which is the plant form of the vitamin. Vitamin K plays an essential role in the formation of certain proteins involved in blood clotting and in building bone. Vitamin content in flaxseed is shown in table no. 4. 

Table No.4: Vitamin Content in Flaxseed.

The mineral content of flaxseed is shown in Table 5.

Table No. 5: The mineral content of flaxseed.

Antinutrients in Flaxseed:

Two compounds, cyanogenic glycosides and linatine an antipyridoxine factor are antinutrients in flaxseed. At the recommended daily intake of about 1–2 tablespoons, approximately 5–10 mg of hydrogen cyanide is released from flaxseed, which is well below the estimated acute toxic dose for an adult of 50–60 mg inorganic cyanide and below the 30–100, mg/ day humans can detoxify. Generally roasting is carried out to eliminate cyanogenic glycosides. In addition to this, trypsin inhibitors and phytic acid are other antinutrients contained in flaxseed. But compared to soybean and canola seeds, their activity they are low.

Conclusion:

Flaxseed (Linum usitatissimum L.) is a globally important agricultural crop grown both for its seed oil as well as its stem fiber. Flaxseed is used as a food source and has many valuable nutritional qualities. Nutritionally, flaxseed has multiple desirable attributes. It is rich in dietary fiber and has a high content of essential fatty acids, vitamins, and minerals. The seeds are composed of ~45% oil, 40% dietary fiber, and 20% protein. Around 73% of the fatty acids in flaxseed are polyunsaturated. Approximately 50% of the total fatty acids consist of α-linolenic acid (ALA), a precursor for many essential fatty acids in the human diet.

Flaxseed is the richest source of plant lignans, which are phytoestrogens and serve as precursors in the production of mammalian lignans. The use of flaxseed by incorporating various products will help to promote healthy living as well as will prevent lifestyle-oriented diseases.

References:

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ABOUT AUTHOR : 

Mrs. S. N. Chaudhari
Assistant Professor
Department of Food Science and Technology
K. Wagh College of Food Technology,
Saraswati nagar, Nashik-422003, Maharashtra