Flaxseed, or linseed (Linum usitatissimum), is an ancient crop that has been cultivated and used specifically for its fibre as well as a health food. In North America, “flaxseed” is the preferred term for flax used in human consumption, whereas Europeans use the term “linseed” for edible flax. Environmental factors can have an impact on fatty acid distribution in flaxseed in addition to oil content. Growing conditions and variety can influence the unsaturated fatty acid content of flaxseed. In contrast, the environment may also have an undesirable impact on flaxseed composition.
Early and late frosts, heat damage and drought can have detrimental effects on flaxseed quality. Consumption of flaxseed is being observed in both food and medicine, owing to it being a top source of omega-3 fatty acids, linolenic acid and lignans (Oomah and Mazza, 2000). Currently, industrial use is the main factor that has been driving the demand for flaxseed oil. Since it helps to improve lipid profiles, flaxseed and flaxseed oil are described as potentially useful foods to reduce cardiovascular risk factors. Omega-3 fatty acids, which are found in flaxseed, are anti-inflammatory and anti-arrhythmic (Simopoulos, 1999).
According to Madhusudhan et al. (2000), flaxseed has been an essential source of omega-3 fatty acids for people who don’t eat fish. Flaxseed typically has a flat, oval shape with a pointed top and measures 2.5 x 5.0 x 1.5 mm, according to Freeman (1995). It consists of four parts: the coat of the seed or testa, the pair of embryos, and the axis of the embryo. People and animals both consume it, but primarily for the oilseed. Flaxseed is one of the oldest crops because of its functional use, good nutritional composition and high content. Flaxseed also succeeds in controlling many diseases, like hyperlipidemia. Vijaymohan, 2006; Jainu et al., 2006); colon tumor (Natrajan et al., 2005); mammary cancer (Thompson, 13766; Rickard et al., 1376; Chen and Wan (2006); 1997); and flaxseed has atherosclerosis (Oda, 2005; Prasa, 1997). Some attention has been given and research has been done in order to find out the different ways in which flaxseed has positive effects on cardiovascular health.
Flaxseed oil is widely used due to its high content of n-3 PUFA and linoleic acid. However, with the increased amount of PUFA in flaxseed oil, it is rapidly subjected to oxidative rancidity, decreasing its shelf life. As a result, this oil cannot be used as cooking oil but only as salad oil, (Daun et al., 2001). In traditional times, flaxseed oil was extracted as other oils, as it includes the same processes like cleansing, blistering, preparing, thumbing, etc., and other steps through which solvent can be removed so as to yield the oil. This process consumes more heat and flaxseed oil is unstable under heat, resulting in a decrease in its nutritional properties, (Shukla, 2003). However, in modern times, the oil extraction process is different and focuses on extracting oil at low temperatures.
Origin and History
Linseed belongs to the genus Linum, which consists of 230 species (Heywood, 1993). There is a total of five sections: Linum, Linastrum, Cathartolinum, Basylinum and Syllinum. It differs according to the number of chromosomes, different parameters of the flower and intrinsic factors, (Gill, 1987). It is considered an economically important and traditional crop for fibre and oil. Linseed is generally known as Atasi, Pesi, Phesi or Tisi in Odia (Sankari, 2000). People have been cultivating flaxseeds since 3000 BC. In ancient times, flaxseed fibre was used for cloth manufacturing in Europe in Neolithic times (the New Stone Age). In the past, flaxseed was first seen in the “Fertile Crescent,” on the east side of the Mediterranean Sea, on the side of India, and further cultivated there too (Zeven and Zhukovsky, 1975). The generic name was Linum, in which ‘line’ defines thread, which further gave it many applications in ancient times.
Linseed was first cultivated in the Central Asiatic Center, Near Eastern Center, Mediterranean Center, and Abyssinian Center. Further, it is spread in other parts of Asia, southward to India. According to one theory, the source of Indo-Gangetic types of linseed originates from the crossing of Linum usitatissimum with Linum strictum and Linum usitatissimum with Linum perenne. The origin species were Linum usitatissimum and Linum angus. Both of them are winter crops that have thin stems but abundant branches with small blue flowers. In Switzerland, lake dwellers were the ones who cultivated them the most.
The proximate composition of protein in flax seed is 22 g per 100 g and the seed proceeds through different conditions like dehusking and defatting, which can affect the protein content. The protein content of the husk of the seed is lower. Some amino acids are rich in flax seeds, like arginine, aspartic acid and glutamic acid and some are in moderate concentration, like lysine, methionine and cysteine, (Chung et al., 2005). Linseed oil is not suitable for edible purposes. Therefore, it is used mainly in paints and plastics for industrial purposes. However, genetic improvement can change linseed oil. (Green, 1989)
Protein content in flaxseed ranges from 10.5% (Bajpai et al., 1985) to 31% (varying according to protein and oil content). Generally, protein values are above 36% (Naqvi et al., 1987). Solubility of proteins differ with differing solutions, as solubility is 42–52% in water, 34–47% in 5% NaCl and 1-2% in NaOH. Flax oil is the most essential part of this seed, which contains 39 g per 100 g of dry matter (Daun et al., 2003; Oomah, 2003). The oil mainly consisted of the cotyledon part of the seed. Appropriate temperature range and moisture leads to the maturity of good-quality oil content in seed. Omega-3 fatty acid is the maximum amount of fatty acid present in seeds. Fatty acids contain a total of 48% lipid concentration, which is recommended for a normal diet. (Coskuner and Karababa 2007) Because of its alpha-linolenic concentration, the seed is considered a functional food. (Bozan and Temelli, 2008)
Phenolic compounds in a proper quantity are also present in flax seed, which are known as lignans and make up the total fat percentage after the final extraction of the whole flax seed, (Oomah, 2003). Phenolic compounds like alpha-linolenic, linoleic, oleic, cotyledons, triacylglycerols at 98%, oleic and oleic are constituted in cotyledons. Flaxseed oil contains 98%, with a lower content of phospholipids at 0.9% and free fatty acids at 0.1%, (Mueller et al., 2010). Apart from linolenic omega-3, linoleic acid, oleic acid, some other constituents are also present at high concentrations.
Flaxseed oil is known for its low concentration of saturated fatty acids and high concentration of unsaturated fatty acids. In the fatty acid table, linolenic acid is 58.28–57.08, linoleic acid is 15.60–15.88 and oleic acid is 18.3–18.21, (Jenab et al., 2006). Transsynaptic, trans-p-coumaric acid and P-hydroxybenzoic are the main phenolic compounds present in flaxseed. Flax fibre is flexible, lustrous and soft. Fibres are stronger than cotton fibre, but heaviness and elasticity are lower with wool, silk, cotton, etc. Once ingested, microflora in the large intestine breaks down dietary fibres to produce acids from short-chain carbon dioxide, hydrogen gas, biomass and methane. (Kritchevsky, 1979)
Anti-nutrients like cyanogenic glycosides are contained in linustatin (213–352 mg per 100 g), neo-linustatin (91-203 mg per 100 g) and linamarin (32 mg per 100 g). The concentration of these anti-nutrients may vary on the basis of cropping, climate, etc., (Oomah et al., 1992). In seed-type linseed, the amount of glycoside is less than in fibre-type linseed. In fiber-type linseed, the immature seed contains more glycosides than the ripened one. The total concentration of cyanogenic glycosides is 250–550 mg per 100 g (Singh et al., 2011). These anti-nutrients have adverse effects, since when these substances enter the intestine, they release hydrogen cyanide (a respiratory invader) that combines with glycosidase to produce thiocyanates, which hinder iodine uptake by the thyroid gland. This can lead to disorders caused by iodine deficiency like goiter and cretinism.
Different types of thermal processing, like auto-claving and micro-roasting can get rid of these anti-nutrients. This is because these glycosides are destroyed by heat or by glycosidase, which is a detoxifying enzyme that releases hydrogen cyanide, which can be gotten rid of by steam evaporation, (Cunnane et al., 1993; Yamashita et al., 2007). An anti-nutrient, phytic acid, is present in linseed, which is about 223–333 g/kg (Oomah et al., 1996). It affects the digestion of magnesium, calcium, iron and zinc. They also combine with protein and mineral absorption, as this anti-nutrient forms protein and mineral complexes, (Erdman, 1979; Akande et al., 2010). Soybean and canola adversely affect human health more, as compared to flaxseed anti-nutrients, (Ganorkar and Jain, 2013). Due to these anti-nutrient factors, it is also more effective as a trypsin inhibitor than soybean and canola.
After experimenting, there are no such antioxidant effects on human health after consumption. Lignans are important constituents of linseed, which has a wide range of biological activity. Secoisolariciresinol Diglucoside (SDG) is the main lignan that has the properties of both an antioxidant and a phytoestrogenic, (Toure and Xueming, 2010). Due to this phenolic compound, flaxseed has become the richest source of plant lignan. Other lignans are matairesinol, secoisolariciresinol and a small amount of pino resinol, Isolariciresinol, and dimethoxy secoisolariciresinol, (Herchi and Sakouhi, 2011; Sicilia and Honig, 2003).
The concentration of phenolic acid in flaxseed varies from 800-1000 mg per 100 g of seed. 300–500 mg per 100 g of esterified phenolic compound can be found in seed (Shahidi, 2004). Soluble phenolic acid is 54% and non-soluble is 29% of total flaxseed flour, (Charlet ,2002; Bensaddek, 2002). Major phenolic acids are trans-ferulic acid and trans-cinnamic acid. Minor phenolic compounds are p coumaric acid, sinapic acid, trans caffeic, chlorogenic, gallic, hydroxybenzoic, protocatechuic which are present in dehulled and defatted flaxseed, (Charlet,2002; Bensaddek, 2002). Other phenolic acids are ferulic acid and vanillic acid, p-coumaric, (Eliasson,2003; Eldin, 2003).
Therapeutic Use of Flaxseed
In numerous diseases like atherosclerosis, rheumatoid arthritis and cardiovascular disease, there is a role for inflammatory mediators. Inflammatory cytokines are helpful in atherosclerosis, (Young, 2002; Libby, 2002). Flaxseed oil is very helpful in regulating inflammation at an appropriate level. CRP, SAA and IL-6 cannot be treated by intaking flaxseed oil for 8 weeks in an adult, (Nelson et al., 2007), but can be treated if 15 ml of oil is consumed daily for 12 weeks. (Paschos, 2005)
Flaxseed oil prevents platelet aggregation, which is a result of thrombin and fibrinogen. If an adult mother intakes 40 g of flaxseed oil per day for 23 days, it can reduce platelet aggregation, (Freese, 1997). In rats, there is no visible coagulation factor when the rat is fed flaxseed oil, (Sinclair, 1999). Due to flaxseed’s high content of soluble fibre, eating it can control how much glucose enters the blood, which may result in a decrease of 10.7% from the baseline after consumption. (Lemay et al. 2002)
Uses of different components in flaxseed
Application of Flaxseed gums in Food Industry
Protein in flaxseed contains polysaccharide gums, which can be used as meat emulsion, canned fish sauce and ice cream, (Dev and Quesnel, 1989). Flaxseed gums have better emulsion stabilizing effects as compared to gelatin. Adding flaxseed gums to meat products leads to fat loss during cooking and there is decrease in firmness, which leads to poor gelling properties. In ice cream, adding of the gums may lead to increase in viscosity and specific gravity.
About the Authors:
Dr. Sukriti Singh and Dr. Anuradha Mishra
Department of Food Science & Technology,
MMICT & BM (HM), MMDU, Mullana.
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