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Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower
Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower HK Woodfield and JL Harwood, Cardiff University, Cardiff, UK Ó 2017 Elsevier Ltd. All rights reserved.
The total world demand for fats and oils has risen continuously at a rate of around 5% for the last 50 years, and there is no sign that this will slow. Presently about 75% of the total is used for food, 9% for animal feed with the remainder having industrial applications such as for biofuel or renewable chemicals and their precursors. Oilseeds provide about 56% of the total fats and oils with soybean, oilseed rape, and sunflower contributing 22%, 12%, and 9%, respectively (Table 1). Linseed oil contributes much less but is an interesting product with both direct industrial and nutraceutical uses.
Linseed Oil The flax plant (Linum usitatissimum) is grown to yield either fiber (linen) or oil with different varieties being used for each purpose. The oil (linseed oil) is enriched in a-linolenic acid, an n-3 polyunsaturated fatty acid (PUFA), which is important nutritionally as well as being prone to oxidation and, hence, is a drying oil with many industrial uses. However, production of linseed oil has declined over the last three decades as the availability of other compounds of industrial utility (e.g., synthetic alkyd resins) has increased. The latter have the drying properties of linseed oil without its yellowing characteristics. About 600 Kt of oil are produced each year with the EU (26%), the USA (22%), China (21%), and India (11%) as major producers. At one time Argentina, Canada, and the USSR were significant suppliers. Typical lipid contents of linseed and linola oils are shown in Table 2. Linola oil is the result of breeding in Australia and Canada where an almost complete absence of D15-desaturase activity has led to the oil with virtually no a-linolenate and enhanced linoleate (Table 2). Linseed oil for human consumption is usually obtained by cold pressing and mild refining. It is normally traded as flaxseed Table 1
Plant Linseed Rapeseed (LEAR) Rapeseed (HEAR) Soybean Sunflower
Plant seed sources of fats and oils Fatty acid composition (%)
Production (2014) (M tonnes)
% Total
16:0
18:1
18:2
Others a
0.6
0.3
6 3
19 61
24 22
51 14
21.7
11.9
3
16
14
67
40.2 16.8
22.1 9.2
11 6
24 18
53 69
12 7
Other major sources of total fats and oils are oil palm (24%) and animal fats (16%). Fatty acids are abbreviated with the number before the colon showing the number of carbon atoms and the figure afterward indicating the number of double bonds. 16:0 is palmitic acid, 18:1 is oleic acid, and 18:2 is linoleic acid. a Linseed ¼ 48% a-linolenic acid; rapeseed (LEAR) ¼ 10% a-linolenic acid; rapeseed (HEAR) ¼ 10% eicosenoic acid, 46% erucic acid; soybean ¼ 7% a-linolenic acid. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
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oil to distinguish it from linseed oil for industrial use. It is generally used as a nutritional supplement but has been used traditionally in Europe in ethnic foods (e.g., quark) because of its distinctive taste. With the increasing recognition of the health benefits of dietary n-3 PUFA, flaxseed oil consumption as a nutraceutical has gone up. Although the conversion of its component a-linolenate to the long-chain PUFAs, EPA (eicosapentaenoic), and DHA (docosahexaenoic) acids is poor, it is thought to be sufficient for human requirements under most circumstances. Flaxseeds themselves are also consumed and provide fiber and lignans as well as oil. There is a good content of the antioxidant tocopherols, which are almost exclusively g-tocopherol. Linola oil is used as an alternative spread to sunflower oil. As might be expected from the overall fatty acid composition (Table 2), the major triacylglycerol species in flaxseed oil are those containing linoleic and a-linolenic acids (LLL, LLLn, LLnLn, and LnLnLn). Because of its high content of a-linolenate, linseed oil is a high-quality drying oil that forms a durable film on exposure to air. It is used in the manufacture of coatings, lacquers, paints, stains, and varnishes with minor utilization for linoleum, printing ink, putty, or soap.
Oilseed Rape Oilseed rape (Brassica napus) is a member of the Brassicaceae family, grown as a cold-season annual crop predominantly for the extraction of its oil. Brassica napus is a hybrid species resulting from interspecific breeding between Brassica rapa Table 2
Composition of linseed and linola oils
Iodine value Fatty acid (%) 16:0 18:0 18:1 18:2 18:3 Other Tocopherols (ppm) g-Tocopherol Total Sterols (ppm) b-Sitosterol Campesterol D5Avenasterol Stigmasterol Total
Typical linseed (European range)
Linola
(170–203)
142
6.0 (4–6) 2.5 (2–3) 19.0 (10–22) 24.1 (12–18) 47.4 (56–71) 1.0 (1–2)
5.6 4.0 15.9 71.8 2.0 0.7
430–575 440–588
471 507
1932 1218 546 378 4200
1608 801 492 164 3095
Fatty acid abbreviations as for Table 1, and 18:0 is stearic acid and 18:3 is a-linolenic acid. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Encyclopedia of Applied Plant Sciences, 2nd edition, Volume 3
http://dx.doi.org/10.1016/B978-0-12-394807-6.00212-4
Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower and Brassica oleracae. Due to this hybridization event, oilseed rape is allotetraploid (containing four genomes from two different species), or more specifically, amphidiploid (containing two diploid genomes). Historically, oilseed rape was high in erucic acid (22:1) (which had poor nutritional properties) and glucosinolates which gave the oil an unpleasant bitter taste, consequently the oil was mainly put to industrial uses rather than for human or animal consumption. Cultivars with low glucosinolates and low erucic acid were developed via conventional breeding which were more palatable. These varieties were initially produced in Canada with the trade name Canola, which has since become the common term for these ‘double-low’ cultivars in many English-speaking countries, especially in North America and Australia. Europe still calls the crop ‘rapeseed,’ using the terms HEAR and LEAR for high- and low-erucic acid varieties, respectively. Other cultivars have since been bred with various oil compositions including low-linolenic and high-oleic varieties. Oilseed rape is the third largest source of plant-derived oil in the world after palm oil and soybean, with approximately 24 million tonnes being produced per year. Production has been steadily rising since the crop entered the food market in the 1970s and is predicted to continue in this upward trend as global oil consumption increases. Oilseed rape is grown predominantly in Western Europe, Canada, China, and India. Production values of rapeseed from the major global growers are shown in Table 3. Typically, canola varieties of oilseed rape contain palmitic (4%), stearic (2%), oleic (62%), linoleic (22%), and a-linolenic (10%) acids. A comparison of the fatty acid composition of LEAR and HEAR rapeseed oil is shown in Table 4. There are also a large number of minor fatty acids present such as those with an odd number of carbon atoms, branched chains, and trans-unsaturation. The most predominant lipid class found in oilseeds is triacylglycerols (TAGs), which act as high-energy storage compounds (yielding high energy/g) in the place of the carbohydrate stores such as the starch found in other crop seeds. The major TAGs found in canola oil are OOO (22%), LOO (22%), LnOO (10%), LLO (9%), LnLO (8%), LOP (6%), and POO (5%). Table 5 shows the major triacylglycerol (TAG) species found in three varieties of oilseed rape, each having a distinctive profile according to their differing fatty acid contents. The distribution of fatty acids on the glycerol backbone is similar to that seen in other vegetable oils. Saturated fatty acids are mainly seen at positions sn-1 and sn-3 while linoleic and linolenic acids are found at sn-2. Positional distribution of the major fatty acids in HEAR are shown in Table 6.
Table 3
Rapeseed production by country Rapeseed production per year in millions of tonnes
Country
2000
2007
2012
European Union Canada China India
11.3 7.2 11.3 5.8
18.4 9.6 10.5 7.4
19.2 15.4 14.0 6.8
Source: FAO STAT.
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Table 4 Fatty acid composition of rapeseed oils expressed as percentages
Total saturated acids 16:0 18:0 Total monounsaturated acids 18:1 20:1 22:1 Total polyunsaturated acids 18:2 18:3
LEAR
HEAR
5.1 3.6 1.5 63.2 61.6 1.4 0.2 31.3 21.7 9.6
5.0 4.0 1.0 69.9 14.8 10.0 45.1 23.2 14.1 9.1
For abbreviations see Tables 1 and 2, 20:1, eicosenoic acid (n ¼ 9); 22:1, erucic acid (docosenoic acid, n-9). Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Major triacylglycerol species (wt%) in rapeseed oil
Table 5
LnLO LLO LnOO LnOP LOO LOP OOO POO StOO PPP LLP LOSt LLL LnLL LnLnO Others
Canola oil
Low-linolenic canola oil
High-oleic canola oil
7.6 8.6 10.4 2.1 22.5 5.7 22.4 4.6 2.6 0.1 1.4 1.6 1.3 1.4 1.7 6.0
1.7 11.0 2.6 0.5 28.4 4.2 32.8 4.8 2.4 1.4 1.1 1.9 1.6 0.0 0.4 5.2
1.5 1.1 8.6 1.1 12.7 2.2 49.5 7.7 5.0 2.8 0.8 1.0 0.2 0.3 0.1 5.4
Abbreviations: P, palmitate; St, stearate; O, oleate; L, linoleate; Ln, alphalinolenate. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Positioning of the major fatty acids in HEAR
Table 6
sn-1 sn-2 sn-3
16:0
18:0
18:1
18:2
18:3
20:1
22:1
5.6 1.6 4.5
1.9 0.4 1.7
16.5 33.4 5.6
1.2 39.3 7.4
3.3 21.3 1.3
17.4 1.9 12.0
50.2 0.8 61.3
For fatty acid abbreviations see Table 4. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
LEAR cultivars (canola) have much lower levels of saturated fatty acids than any other commodity oil and have a favorable omega-6/omega-3 ratio, both of which are considered to be healthy qualities, making oilseed rape popular in the food industry. Rapeseed is put to various culinary uses, for instance in salad oils, frying and cooking oils, spreads, and shortenings. HEAR varieties are used for industrial purposes such as soap
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Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower
production, synthetic rubbers, chainsaw oil, and illuminant in the printing process. Rapeseed oil has also become more prevalent in the biofuel industry, especially in Europe which aims for all EU countries to be using 10% biofuel in total transport fuels by 2020. Rapeseed oil is either used directly in heated fuel systems, or the methyl esters are mixed with mineral oil to produce a more sustainable biodiesel. Across the world approximately 60% of rapeseed oil is used for food, 38% for industrial uses, and 3% for feed; however, these proportions vary significantly by region. For instance, in Europe the use of rapeseed oil is biased toward industrial uses (69% compared to 22% for food) whereas Northern America has a more even weighting between food and industrial applications (47% and 53%, respectively). Although grown predominantly for its oil, the processing of rapeseed produces a high protein content meal as a by-product which is used for animal feed. This rapeseed meal, or oil cake, is also used in certain parts of the world as a fertilizer. Oilseed rape is a highly productive plant with a diverse range of applications in both industrial and consumer markets. There are many breeding programs underway to improve on the quality and quantity of oil produced by oilseed rape. In addition, oilseed rape is relatively easy to transform. Genetically modified varieties with herbicide tolerance such as Roundup ready and LibertyLink are widely grown across North America, unlike Europe where the laws governing the use of genetically modified crops are much more stringent. However, as of September 2014 three transgenic oilseed rape varieties have been authorized to be grown in the EU so European attitudes toward genetic modification of crops may be shifting. The B. napus genome was sequenced in 2014, a tool which will greatly assist efforts to further develop the crop, both through conventional breeding programs and genetic modification.
Soybean Oil Soybean oil is second only to palm oil in amount and provides about 22% of the total world fats and oils (Table 1). It is grown for its high-quality protein meal, but the seed contains just over 20% oil. Production is greatest in China (26%), the USA (21%), Brazil (17%), and Argentina (16%). While crude soybean oil contains significant quantities of phospholipids (1.5–2.5%), unsaponifiable matter (1.6%), and traces of metals, after refining it is 99% triacylglycerol. The phospholipid concentrate removed by degumming is a valuable by-product known as lecithin and is a notable source of commercial phospholipids. Crude lecithin is about 50% phospholipids, 34% TAG along with 7% glycolipids and 7% carbohydrates. By ‘deoiling,’ the TAGs are substantially removed to leave about 90% polar lipids (29% PtdCho, 29% PtdEtn, and 32% PtdIns þ glycolipids). These polar lipids can be separated further or modified by chemical and enzymatic reactions. Lecithin, with various compositions, is used in a range of food products (including chocolate), in animal feed, cosmetics, and pharmaceutical preparations. The fatty acid composition of typical commodity soybean oil is shown in Table 7. It is highly unsaturated oil and was originally prized for this. However, its enrichment in linoleic acid presents a number of problems – both nutritional as well as
Table 7
Fatty acid compositions of different soybean oils Fatty acid composition (%)
Oil type
16:0
18:0
18:1
18:2
18:3
Commodity Low saturated High palmitic High stearic High saturated High oleic Low linolenate
11 3 24 10 23 8 12
4 2 5 24 19 2 6
23 30 19 40 9 83 37
54 59 45 20 40 3 43
8 6 7 6 10 4 2
Average values for different analyses shown. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
for its commercial utilization. Moreover, the ratio of linoleic to a-linolenic acid is over 6, which is higher than a nutritionally desirable ratio of 4. As a result, several new lines have been produced by breeding or genetic manipulation (Table 8). The high-oleic lines are already popular because of their perceived health benefits and better industrial utility. Efforts have also been made to reduce the a-linolenate content so as to improve oxidative stability and increase shelf-life but, of course, that also removes the nutritionally desirable n-3 PUFA. Light hydrogenation has been used to produce a-linolenate and more severe hydrogenation to enable spreads (margarines) to be produced. Although this process leads to increased saturated and monosaturated fatty acid contents, it can also cause trans unsaturates to be produced. Trans-fatty acids are considered harmful, and their content in oils must be severely restricted by legislation in many countries. The multiple uses that need to be made of soybean oil are a particular problem in the USA, where the fat in food is almost entirely derived from soybeans. This is where the new varieties (Table 7) could be particularly helpful, provided that the regulatory approval for their use as commodity oils does not become too expensive. The distribution of fatty acids on the glycerol backbone of TAG is shown in Table 8. Because of the selectivity of the acyltransferases involved in the production of plant TAGs, including that in soybean, the sn-1 position contains the highest proportion of saturated fatty acids while the sn-2 position has the lowest. Typically, the sn-3 position is intermediate and that is seen in Table 7. As mentioned above, hydrogenation of soybean oil leads to trans-double bonds mainly in the range D6–D14 with the D10 and D11 acids predominating. Although trans-fatty acids are harmful and, hence, virtually completely removed from modern foods, it can be noted that several natural products
Table 8
The fatty acid composition of a typical soybean oil
Total oil sn-1 position sn-2 position sn-2 position
16:0
18:0
18:1
18:2
18:3
11.5 19.5 2.8 13.0
4.3 7.6 1.1 5.1
25.4 22.0 22.7 31.7
52.0 43.1 66.3 44.8
6.9 7.9 7.1 5.4
Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower (e.g., ruminant milk fats also contain significant trans-fatty acids from biohydrogenation reactions in the rumen. Simultaneous to the hydrogenation process, the iodine value (a measure of unsaturation) goes down progressively as the method is made more severe to produce different end products (Table 9). Apart from lecithin, there are a number of valuable byproducts from soybeans and their processing. Thus, soybean deodorizer distillate contains 11% tocopherols and 18% sterols. These compounds were only 0.15–0.21% and about 0.33%, respectively, in the oil. The main sterols are b-sitosterol (56%), campesterol (29%), and stigmasterol (20%). The sterols are used for dietary purposes as phytosterols where they reduce cholesterol absorption in the intestine. They are also modified chemically to produce about three-quarters of the world supply of pharmaceutical steroids. Typical solventextracted soybean oil contains 1.37 g kg1 of tocopherols of which g-tocopherol (64%) and d-tocopherol (25%) are the main components. Not only are these useful by-products, they act as antioxidants in soybean oil itself. Soybean oil is used for a variety of food purposes either with or without processing. These include cooking and salad oils, spreads and shortenings, mayonnaise, and salad dressings. There are a host of nonfood uses which include semidrying oil, biofuel, plasticizer, and in inks and lubricants. Some 12–13% of soybean oil currently has nonfood uses. One area of current research involves developing improved soybean oil–based lubricants with better oxidative stability and cold-weather fluidity. Currently, products are available for small engines. Soybean oil has been modified for use as a diluent in alkyd coatings, alkyd paints, and inks. Plastic composites are cured into permanent shapes on exposure to a catalyst or a source of heat. Such composites can use soybean oil as a source of unsaturated polyesters or polyurethanes, and they are used in the agricultural equipment, construction, and transportation markets. Polyurethanes are formed from polyols and di-tri-isocyanate with various additives. A polyol product from soybean is used as a substitute for petroleum-based polyols and is utilized for elastomers, flexible molded foams, and rigid structural polyurethane foams. Soap stock (from the neutralization processing step) is a recovered by-product, and acidification yields unesterified fatty acids for use mainly in animal feeds. The low cost of the
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latter product has led to investigation of its use for biodiesel production. However, neither that nor the methyl esters produced from soybean oil are entirely satisfactory as biodiesels.
Sunflower Oil Sunflower (Helianthus cannus) is an ancient crop, imported from the Americas to Spain in the fourteenth century. It is grown mainly in the Ukraine, Russia, some countries in the EU, and Argentina. Present-day production of oil is over 15 million tonnes, which places it fourth in world oil crops (Table 1). Original varieties were rich in linoleic acid but several important cultivars with various oil compositions have been produced. The fatty acid composition of standard sunflower oil together with other varieties are shown in Table 10. Traditional sunflower oil is obtained in 40–50% yield following solvent extraction, contains up to 75% linoleic acid with virtually no a-linolenate. Palmitate and stearate are present in equivalent amounts while oleate can represent up to 30%. It is widely used as cooking oil and is an important component of soft spreads especially in Western Europe. Its major TAG species are LLL (27%), LLO (27%), LLP (10%), LOO (10%), and LLS (11%) (see Table 11). Traditional sunflower oil was prized until recently for its health properties in providing the essential fatty acid, linoleate. However, it is now recognized that Western diets, in particular, contain too much n-6 PUFAs, which are metabolized to give mostly inflammatory mediators such as leukotriene B4 and prostaglandin E2. The ratio of n-6/n-3 PUFAs in human diets is usually advised to be about 4 whereas Western diets often have ratios of 15–20. Of course, if sunflower oil is a main source of dietary fat, then the ratio will be high. Partly for this reason (and also because oleate is a very useful renewable for the chemical industry), oleate-enriched varieties have been bred. Sunola (Highsun) comes from a high oleate variety and can contain up to 90% oleate. It is valued as high-quality table oil. Another oil, NuSun, was produced from varieties in the USA and has intermediate levels of oleate (about 60%) and is hoped to replace traditional sunflower oil there. Oils with
Table 10 Fatty acid compositions of oils from traditional and several sunflower lines Table 9 Effect of hydrogenation on iodine values and fatty acid composition of typical soybean oil and specialized oils
Product
Soybean oil (SO) Hydrogenated SO (HSO) Winterized HSO Stearin Shortening oil Margarine oil
Iodine value
% trans
132 113
0 9
16:0 11 11
18:0 4 5
18:1 22 40
18:2 55 41
18:3 7 3
110 97 82 65
9 13 32 40
11 13 11 11
4 7 5 14
42 48 73 75
40 30 11 –
3 2 – –
Fatty acid composition (%)
Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Fatty acid (wt%)
Traditional
HO
HS
HP
UHO
HSHO
16:0 18:0 18:1 18:2 Others AOM (hrs)
6–7 4–5 21–29 58–68 tr-2 10–12
5 3 75 15 2 40–50
3 30 14 50 3 –
26 2 91 2 1 –
4 2 91 2 1 –
5 18 71 3 3 –
Abbreviations: HO, high oleic; HS, high stearic; HP, high palmitic; UHO, ultra high oleic; HSHO, high stearic high oleic; AOM, active oxidation method (using thiobarbituric acid); tr, trace. The HO and HS varieties were produced by chemical mutagenesis, the HP variety by X-ray irradiation while the UHO and HSHO varieties were obtained by breeding. See Salas, J.J., et al., 2014. Biochemistry of high stearic sunflower, a new source of saturated fats. Prog. Lipid Res. 55, 30–42 and Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton for more details.
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Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower Table 11 Molecular species of TAGs (% total) in different sunflower oils Species
Traditional oils
HO
HOHP
LLL OLL PLL OLO PLO/SLL OOO OOPo POO/SOL POPo POP Others
27 29 10 11 10 3 – 4 – tr. 6
6 8 2 10 4 51 – 9 – – –
– – – 1 3 13 9 36 12 19 9
26 26 11 8 13 2 – 5 – – 10
Abbreviations: L, linoleate; O, oleate; P, palmitate; Po, palmitoleate, S, stearate; tr, trace (<0.5); HO, high oleic; HOHP, high oleic high palmitate. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
less linoleate and more oleate have enhanced oxidative stability (Table 10). Because varieties with modified fatty acid composition have been produced without genetic modification (GM), they are suitable for the current European market which is hostile to GM-crops. Like many edible oils, that from sunflower contains appreciable amounts of tocopherols (530–700 ppm – almost entirely the a-isomer) which makes both seeds and their oils good sources of vitamin E. Free sterols represent 72% of the sterol fraction (about 0.3% total oil). Sunflower deodorizer distillate contains about 5% sterols and 6% tocopherols, while the crude oil also has phosphoglycerides (0.8%) and carotenoids (1.5 ppm). Crude sunflower oil contains appreciable wax which causes a haze in unrefined oil. Sunflower seeds are often used as birdseed, in breakfast cereals and on breads. The hulls have a limited market as poultry litter and in high-fiber products. It has also been considered for biodiesel production – especially the higholeic variety. Characteristics such as viscosity, cetane number, and pour points are generally satisfactory although longerterm tests have shown a buildup of combustion chamber deposits with piston ring sticking and engine failure due to decreased fuel atomization. Overall only about 3–4% of the total sunflower oil is used for industrial purposes.
See also: Biotechnology: Acyl Lipids; Oil Deposition; Oils. Energy and Fibre Crops: Biofuels. Tropical Agriculture: Oil Palm.
Further Reading Ayorinde, F.O., 2000. Determination of the molecular distribution of triacylglycerol oils using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Lipid Technol. 12, 41–44. Barcelo-Coblijin, G., Murphy, E.J., 2009. Alpha-linolenic acid and its conversion to longer chain n-3 fatty acids: benefits for human health and a role in maintaining tissue n-3 fatty acid levels. Prog. Lipid Res. 48, 355–374. Cunnane, S.C., 2003. Problems with essential fatty acids: time for a new paradigm? Prog. Lipid Res. 42, 544–568. Green, A.G., Dribnenki, J.C.P., 1994. Linola – a new premium polyunsaturated oil. Lipid Technol. 6, 29–33. Grompone, M.A., 2005. Sunflower oil. In: Shahidi, F. (Ed.), Bailey’s Industrial Oil and Fat Products, sixth ed., vol. 2. Wiley Interscience, , New York, pp. 655–730. Gong, Y., et al., 2014. Metabolic engineering of microorganisms to produce omega-3 very long chain polyunsaturated fatty acids. Prog. Lipid Res. 56, 19–35. Guinda, A., et al., 2003. Chemical and physical properties of a sunflower oil with high levels of oleic and palmitic acids. Eur. J. Lipid Sci. Technol. 105, 130–137. Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton. Gupta, M.K., 2002. Sunflower oil. In: Gunstone, F.D. (Ed.), Vegetable Oils in Food Technology – Composition, Properties and Uses. Blackwell Publishing, Oxford, pp. 128–156. Hammond, E.G., et al., 2005. Soybean oil. In: Shahidi, F. (Ed.), Bailey’s Industrial Oil and Fat Products, sixth ed., vol. 2. Wiley Interscience, New York, pp. 577–653. Kochhar, S.P., 2002. Sesame, rice-bran and flaxseed oils. In: Gunstone, F.D. (Ed.), Vegetable Oils in Food Technology – Composition, Properties and Uses. Blackwell Publishing, Oxford, pp. 297–326. Lands, B., 2014. Historical perspectives on the impact of n-3 and n-6 nutrients on health. Prog. Lipid Res. 55, 17–29. Murphy, D.J. (Ed.), 2005. Plant Lipids: Biology, Utilisation and Manipulation. Blackwell Publishing, Oxford. Salas, J.J., et al., 2014. Biochemistry of high stearic sunflower, a new source of saturated fats. Prog. Lipid Res. 55, 30–42. Thompson, L., Cunnane, S. (Eds.), 2003. Flaxseed in Human Nutrition, second ed. AOCS Press, Campaign, IL. Wolff, R.L., et al., 1998. Occurrence and distribution profiles of trans-18:1 acids in edible fats of natural origin. In: Sebedio, J.L., Christie, W.W. (Eds.), Trans Fatty Acids in Human Nutrition. The Oily Press, Dundee, pp. 1–34.
Relevant Websites http://faostat3.fao.org – FAO STAT. http://lipidlibrary.aocs.org – The Lipid Library.
The total world demand for fats and oils has risen continuously at a rate of around 5% for the last 50 years, and there is no sign that this will slow. Presently about 75% of the total is used for food, 9% for animal feed with the remainder having industrial applications such as for biofuel or renewable chemicals and their precursors. Oilseeds provide about 56% of the total fats and oils with soybean, oilseed rape, and sunflower contributing 22%, 12%, and 9%, respectively (Table 1). Linseed oil contributes much less but is an interesting product with both direct industrial and nutraceutical uses.
Linseed Oil The flax plant (Linum usitatissimum) is grown to yield either fiber (linen) or oil with different varieties being used for each purpose. The oil (linseed oil) is enriched in a-linolenic acid, an n-3 polyunsaturated fatty acid (PUFA), which is important nutritionally as well as being prone to oxidation and, hence, is a drying oil with many industrial uses. However, production of linseed oil has declined over the last three decades as the availability of other compounds of industrial utility (e.g., synthetic alkyd resins) has increased. The latter have the drying properties of linseed oil without its yellowing characteristics. About 600 Kt of oil are produced each year with the EU (26%), the USA (22%), China (21%), and India (11%) as major producers. At one time Argentina, Canada, and the USSR were significant suppliers. Typical lipid contents of linseed and linola oils are shown in Table 2. Linola oil is the result of breeding in Australia and Canada where an almost complete absence of D15-desaturase activity has led to the oil with virtually no a-linolenate and enhanced linoleate (Table 2). Linseed oil for human consumption is usually obtained by cold pressing and mild refining. It is normally traded as flaxseed Table 1
Plant Linseed Rapeseed (LEAR) Rapeseed (HEAR) Soybean Sunflower
Plant seed sources of fats and oils Fatty acid composition (%)
Production (2014) (M tonnes)
% Total
16:0
18:1
18:2
Others a
0.6
0.3
6 3
19 61
24 22
51 14
21.7
11.9
3
16
14
67
40.2 16.8
22.1 9.2
11 6
24 18
53 69
12 7
Other major sources of total fats and oils are oil palm (24%) and animal fats (16%). Fatty acids are abbreviated with the number before the colon showing the number of carbon atoms and the figure afterward indicating the number of double bonds. 16:0 is palmitic acid, 18:1 is oleic acid, and 18:2 is linoleic acid. a Linseed ¼ 48% a-linolenic acid; rapeseed (LEAR) ¼ 10% a-linolenic acid; rapeseed (HEAR) ¼ 10% eicosenoic acid, 46% erucic acid; soybean ¼ 7% a-linolenic acid. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
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oil to distinguish it from linseed oil for industrial use. It is generally used as a nutritional supplement but has been used traditionally in Europe in ethnic foods (e.g., quark) because of its distinctive taste. With the increasing recognition of the health benefits of dietary n-3 PUFA, flaxseed oil consumption as a nutraceutical has gone up. Although the conversion of its component a-linolenate to the long-chain PUFAs, EPA (eicosapentaenoic), and DHA (docosahexaenoic) acids is poor, it is thought to be sufficient for human requirements under most circumstances. Flaxseeds themselves are also consumed and provide fiber and lignans as well as oil. There is a good content of the antioxidant tocopherols, which are almost exclusively g-tocopherol. Linola oil is used as an alternative spread to sunflower oil. As might be expected from the overall fatty acid composition (Table 2), the major triacylglycerol species in flaxseed oil are those containing linoleic and a-linolenic acids (LLL, LLLn, LLnLn, and LnLnLn). Because of its high content of a-linolenate, linseed oil is a high-quality drying oil that forms a durable film on exposure to air. It is used in the manufacture of coatings, lacquers, paints, stains, and varnishes with minor utilization for linoleum, printing ink, putty, or soap.
Oilseed Rape Oilseed rape (Brassica napus) is a member of the Brassicaceae family, grown as a cold-season annual crop predominantly for the extraction of its oil. Brassica napus is a hybrid species resulting from interspecific breeding between Brassica rapa Table 2
Composition of linseed and linola oils
Iodine value Fatty acid (%) 16:0 18:0 18:1 18:2 18:3 Other Tocopherols (ppm) g-Tocopherol Total Sterols (ppm) b-Sitosterol Campesterol D5Avenasterol Stigmasterol Total
Typical linseed (European range)
Linola
(170–203)
142
6.0 (4–6) 2.5 (2–3) 19.0 (10–22) 24.1 (12–18) 47.4 (56–71) 1.0 (1–2)
5.6 4.0 15.9 71.8 2.0 0.7
430–575 440–588
471 507
1932 1218 546 378 4200
1608 801 492 164 3095
Fatty acid abbreviations as for Table 1, and 18:0 is stearic acid and 18:3 is a-linolenic acid. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Encyclopedia of Applied Plant Sciences, 2nd edition, Volume 3
http://dx.doi.org/10.1016/B978-0-12-394807-6.00212-4
Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower and Brassica oleracae. Due to this hybridization event, oilseed rape is allotetraploid (containing four genomes from two different species), or more specifically, amphidiploid (containing two diploid genomes). Historically, oilseed rape was high in erucic acid (22:1) (which had poor nutritional properties) and glucosinolates which gave the oil an unpleasant bitter taste, consequently the oil was mainly put to industrial uses rather than for human or animal consumption. Cultivars with low glucosinolates and low erucic acid were developed via conventional breeding which were more palatable. These varieties were initially produced in Canada with the trade name Canola, which has since become the common term for these ‘double-low’ cultivars in many English-speaking countries, especially in North America and Australia. Europe still calls the crop ‘rapeseed,’ using the terms HEAR and LEAR for high- and low-erucic acid varieties, respectively. Other cultivars have since been bred with various oil compositions including low-linolenic and high-oleic varieties. Oilseed rape is the third largest source of plant-derived oil in the world after palm oil and soybean, with approximately 24 million tonnes being produced per year. Production has been steadily rising since the crop entered the food market in the 1970s and is predicted to continue in this upward trend as global oil consumption increases. Oilseed rape is grown predominantly in Western Europe, Canada, China, and India. Production values of rapeseed from the major global growers are shown in Table 3. Typically, canola varieties of oilseed rape contain palmitic (4%), stearic (2%), oleic (62%), linoleic (22%), and a-linolenic (10%) acids. A comparison of the fatty acid composition of LEAR and HEAR rapeseed oil is shown in Table 4. There are also a large number of minor fatty acids present such as those with an odd number of carbon atoms, branched chains, and trans-unsaturation. The most predominant lipid class found in oilseeds is triacylglycerols (TAGs), which act as high-energy storage compounds (yielding high energy/g) in the place of the carbohydrate stores such as the starch found in other crop seeds. The major TAGs found in canola oil are OOO (22%), LOO (22%), LnOO (10%), LLO (9%), LnLO (8%), LOP (6%), and POO (5%). Table 5 shows the major triacylglycerol (TAG) species found in three varieties of oilseed rape, each having a distinctive profile according to their differing fatty acid contents. The distribution of fatty acids on the glycerol backbone is similar to that seen in other vegetable oils. Saturated fatty acids are mainly seen at positions sn-1 and sn-3 while linoleic and linolenic acids are found at sn-2. Positional distribution of the major fatty acids in HEAR are shown in Table 6.
Table 3
Rapeseed production by country Rapeseed production per year in millions of tonnes
Country
2000
2007
2012
European Union Canada China India
11.3 7.2 11.3 5.8
18.4 9.6 10.5 7.4
19.2 15.4 14.0 6.8
Source: FAO STAT.
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Table 4 Fatty acid composition of rapeseed oils expressed as percentages
Total saturated acids 16:0 18:0 Total monounsaturated acids 18:1 20:1 22:1 Total polyunsaturated acids 18:2 18:3
LEAR
HEAR
5.1 3.6 1.5 63.2 61.6 1.4 0.2 31.3 21.7 9.6
5.0 4.0 1.0 69.9 14.8 10.0 45.1 23.2 14.1 9.1
For abbreviations see Tables 1 and 2, 20:1, eicosenoic acid (n ¼ 9); 22:1, erucic acid (docosenoic acid, n-9). Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Major triacylglycerol species (wt%) in rapeseed oil
Table 5
LnLO LLO LnOO LnOP LOO LOP OOO POO StOO PPP LLP LOSt LLL LnLL LnLnO Others
Canola oil
Low-linolenic canola oil
High-oleic canola oil
7.6 8.6 10.4 2.1 22.5 5.7 22.4 4.6 2.6 0.1 1.4 1.6 1.3 1.4 1.7 6.0
1.7 11.0 2.6 0.5 28.4 4.2 32.8 4.8 2.4 1.4 1.1 1.9 1.6 0.0 0.4 5.2
1.5 1.1 8.6 1.1 12.7 2.2 49.5 7.7 5.0 2.8 0.8 1.0 0.2 0.3 0.1 5.4
Abbreviations: P, palmitate; St, stearate; O, oleate; L, linoleate; Ln, alphalinolenate. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Positioning of the major fatty acids in HEAR
Table 6
sn-1 sn-2 sn-3
16:0
18:0
18:1
18:2
18:3
20:1
22:1
5.6 1.6 4.5
1.9 0.4 1.7
16.5 33.4 5.6
1.2 39.3 7.4
3.3 21.3 1.3
17.4 1.9 12.0
50.2 0.8 61.3
For fatty acid abbreviations see Table 4. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
LEAR cultivars (canola) have much lower levels of saturated fatty acids than any other commodity oil and have a favorable omega-6/omega-3 ratio, both of which are considered to be healthy qualities, making oilseed rape popular in the food industry. Rapeseed is put to various culinary uses, for instance in salad oils, frying and cooking oils, spreads, and shortenings. HEAR varieties are used for industrial purposes such as soap
36
Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower
production, synthetic rubbers, chainsaw oil, and illuminant in the printing process. Rapeseed oil has also become more prevalent in the biofuel industry, especially in Europe which aims for all EU countries to be using 10% biofuel in total transport fuels by 2020. Rapeseed oil is either used directly in heated fuel systems, or the methyl esters are mixed with mineral oil to produce a more sustainable biodiesel. Across the world approximately 60% of rapeseed oil is used for food, 38% for industrial uses, and 3% for feed; however, these proportions vary significantly by region. For instance, in Europe the use of rapeseed oil is biased toward industrial uses (69% compared to 22% for food) whereas Northern America has a more even weighting between food and industrial applications (47% and 53%, respectively). Although grown predominantly for its oil, the processing of rapeseed produces a high protein content meal as a by-product which is used for animal feed. This rapeseed meal, or oil cake, is also used in certain parts of the world as a fertilizer. Oilseed rape is a highly productive plant with a diverse range of applications in both industrial and consumer markets. There are many breeding programs underway to improve on the quality and quantity of oil produced by oilseed rape. In addition, oilseed rape is relatively easy to transform. Genetically modified varieties with herbicide tolerance such as Roundup ready and LibertyLink are widely grown across North America, unlike Europe where the laws governing the use of genetically modified crops are much more stringent. However, as of September 2014 three transgenic oilseed rape varieties have been authorized to be grown in the EU so European attitudes toward genetic modification of crops may be shifting. The B. napus genome was sequenced in 2014, a tool which will greatly assist efforts to further develop the crop, both through conventional breeding programs and genetic modification.
Soybean Oil Soybean oil is second only to palm oil in amount and provides about 22% of the total world fats and oils (Table 1). It is grown for its high-quality protein meal, but the seed contains just over 20% oil. Production is greatest in China (26%), the USA (21%), Brazil (17%), and Argentina (16%). While crude soybean oil contains significant quantities of phospholipids (1.5–2.5%), unsaponifiable matter (1.6%), and traces of metals, after refining it is 99% triacylglycerol. The phospholipid concentrate removed by degumming is a valuable by-product known as lecithin and is a notable source of commercial phospholipids. Crude lecithin is about 50% phospholipids, 34% TAG along with 7% glycolipids and 7% carbohydrates. By ‘deoiling,’ the TAGs are substantially removed to leave about 90% polar lipids (29% PtdCho, 29% PtdEtn, and 32% PtdIns þ glycolipids). These polar lipids can be separated further or modified by chemical and enzymatic reactions. Lecithin, with various compositions, is used in a range of food products (including chocolate), in animal feed, cosmetics, and pharmaceutical preparations. The fatty acid composition of typical commodity soybean oil is shown in Table 7. It is highly unsaturated oil and was originally prized for this. However, its enrichment in linoleic acid presents a number of problems – both nutritional as well as
Table 7
Fatty acid compositions of different soybean oils Fatty acid composition (%)
Oil type
16:0
18:0
18:1
18:2
18:3
Commodity Low saturated High palmitic High stearic High saturated High oleic Low linolenate
11 3 24 10 23 8 12
4 2 5 24 19 2 6
23 30 19 40 9 83 37
54 59 45 20 40 3 43
8 6 7 6 10 4 2
Average values for different analyses shown. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
for its commercial utilization. Moreover, the ratio of linoleic to a-linolenic acid is over 6, which is higher than a nutritionally desirable ratio of 4. As a result, several new lines have been produced by breeding or genetic manipulation (Table 8). The high-oleic lines are already popular because of their perceived health benefits and better industrial utility. Efforts have also been made to reduce the a-linolenate content so as to improve oxidative stability and increase shelf-life but, of course, that also removes the nutritionally desirable n-3 PUFA. Light hydrogenation has been used to produce a-linolenate and more severe hydrogenation to enable spreads (margarines) to be produced. Although this process leads to increased saturated and monosaturated fatty acid contents, it can also cause trans unsaturates to be produced. Trans-fatty acids are considered harmful, and their content in oils must be severely restricted by legislation in many countries. The multiple uses that need to be made of soybean oil are a particular problem in the USA, where the fat in food is almost entirely derived from soybeans. This is where the new varieties (Table 7) could be particularly helpful, provided that the regulatory approval for their use as commodity oils does not become too expensive. The distribution of fatty acids on the glycerol backbone of TAG is shown in Table 8. Because of the selectivity of the acyltransferases involved in the production of plant TAGs, including that in soybean, the sn-1 position contains the highest proportion of saturated fatty acids while the sn-2 position has the lowest. Typically, the sn-3 position is intermediate and that is seen in Table 7. As mentioned above, hydrogenation of soybean oil leads to trans-double bonds mainly in the range D6–D14 with the D10 and D11 acids predominating. Although trans-fatty acids are harmful and, hence, virtually completely removed from modern foods, it can be noted that several natural products
Table 8
The fatty acid composition of a typical soybean oil
Total oil sn-1 position sn-2 position sn-2 position
16:0
18:0
18:1
18:2
18:3
11.5 19.5 2.8 13.0
4.3 7.6 1.1 5.1
25.4 22.0 22.7 31.7
52.0 43.1 66.3 44.8
6.9 7.9 7.1 5.4
Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower (e.g., ruminant milk fats also contain significant trans-fatty acids from biohydrogenation reactions in the rumen. Simultaneous to the hydrogenation process, the iodine value (a measure of unsaturation) goes down progressively as the method is made more severe to produce different end products (Table 9). Apart from lecithin, there are a number of valuable byproducts from soybeans and their processing. Thus, soybean deodorizer distillate contains 11% tocopherols and 18% sterols. These compounds were only 0.15–0.21% and about 0.33%, respectively, in the oil. The main sterols are b-sitosterol (56%), campesterol (29%), and stigmasterol (20%). The sterols are used for dietary purposes as phytosterols where they reduce cholesterol absorption in the intestine. They are also modified chemically to produce about three-quarters of the world supply of pharmaceutical steroids. Typical solventextracted soybean oil contains 1.37 g kg1 of tocopherols of which g-tocopherol (64%) and d-tocopherol (25%) are the main components. Not only are these useful by-products, they act as antioxidants in soybean oil itself. Soybean oil is used for a variety of food purposes either with or without processing. These include cooking and salad oils, spreads and shortenings, mayonnaise, and salad dressings. There are a host of nonfood uses which include semidrying oil, biofuel, plasticizer, and in inks and lubricants. Some 12–13% of soybean oil currently has nonfood uses. One area of current research involves developing improved soybean oil–based lubricants with better oxidative stability and cold-weather fluidity. Currently, products are available for small engines. Soybean oil has been modified for use as a diluent in alkyd coatings, alkyd paints, and inks. Plastic composites are cured into permanent shapes on exposure to a catalyst or a source of heat. Such composites can use soybean oil as a source of unsaturated polyesters or polyurethanes, and they are used in the agricultural equipment, construction, and transportation markets. Polyurethanes are formed from polyols and di-tri-isocyanate with various additives. A polyol product from soybean is used as a substitute for petroleum-based polyols and is utilized for elastomers, flexible molded foams, and rigid structural polyurethane foams. Soap stock (from the neutralization processing step) is a recovered by-product, and acidification yields unesterified fatty acids for use mainly in animal feeds. The low cost of the
37
latter product has led to investigation of its use for biodiesel production. However, neither that nor the methyl esters produced from soybean oil are entirely satisfactory as biodiesels.
Sunflower Oil Sunflower (Helianthus cannus) is an ancient crop, imported from the Americas to Spain in the fourteenth century. It is grown mainly in the Ukraine, Russia, some countries in the EU, and Argentina. Present-day production of oil is over 15 million tonnes, which places it fourth in world oil crops (Table 1). Original varieties were rich in linoleic acid but several important cultivars with various oil compositions have been produced. The fatty acid composition of standard sunflower oil together with other varieties are shown in Table 10. Traditional sunflower oil is obtained in 40–50% yield following solvent extraction, contains up to 75% linoleic acid with virtually no a-linolenate. Palmitate and stearate are present in equivalent amounts while oleate can represent up to 30%. It is widely used as cooking oil and is an important component of soft spreads especially in Western Europe. Its major TAG species are LLL (27%), LLO (27%), LLP (10%), LOO (10%), and LLS (11%) (see Table 11). Traditional sunflower oil was prized until recently for its health properties in providing the essential fatty acid, linoleate. However, it is now recognized that Western diets, in particular, contain too much n-6 PUFAs, which are metabolized to give mostly inflammatory mediators such as leukotriene B4 and prostaglandin E2. The ratio of n-6/n-3 PUFAs in human diets is usually advised to be about 4 whereas Western diets often have ratios of 15–20. Of course, if sunflower oil is a main source of dietary fat, then the ratio will be high. Partly for this reason (and also because oleate is a very useful renewable for the chemical industry), oleate-enriched varieties have been bred. Sunola (Highsun) comes from a high oleate variety and can contain up to 90% oleate. It is valued as high-quality table oil. Another oil, NuSun, was produced from varieties in the USA and has intermediate levels of oleate (about 60%) and is hoped to replace traditional sunflower oil there. Oils with
Table 10 Fatty acid compositions of oils from traditional and several sunflower lines Table 9 Effect of hydrogenation on iodine values and fatty acid composition of typical soybean oil and specialized oils
Product
Soybean oil (SO) Hydrogenated SO (HSO) Winterized HSO Stearin Shortening oil Margarine oil
Iodine value
% trans
132 113
0 9
16:0 11 11
18:0 4 5
18:1 22 40
18:2 55 41
18:3 7 3
110 97 82 65
9 13 32 40
11 13 11 11
4 7 5 14
42 48 73 75
40 30 11 –
3 2 – –
Fatty acid composition (%)
Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
Fatty acid (wt%)
Traditional
HO
HS
HP
UHO
HSHO
16:0 18:0 18:1 18:2 Others AOM (hrs)
6–7 4–5 21–29 58–68 tr-2 10–12
5 3 75 15 2 40–50
3 30 14 50 3 –
26 2 91 2 1 –
4 2 91 2 1 –
5 18 71 3 3 –
Abbreviations: HO, high oleic; HS, high stearic; HP, high palmitic; UHO, ultra high oleic; HSHO, high stearic high oleic; AOM, active oxidation method (using thiobarbituric acid); tr, trace. The HO and HS varieties were produced by chemical mutagenesis, the HP variety by X-ray irradiation while the UHO and HSHO varieties were obtained by breeding. See Salas, J.J., et al., 2014. Biochemistry of high stearic sunflower, a new source of saturated fats. Prog. Lipid Res. 55, 30–42 and Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton for more details.
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Arable Crops j Oilseed Crops: Linseed, Rapeseed, Soybean, and Sunflower Table 11 Molecular species of TAGs (% total) in different sunflower oils Species
Traditional oils
HO
HOHP
LLL OLL PLL OLO PLO/SLL OOO OOPo POO/SOL POPo POP Others
27 29 10 11 10 3 – 4 – tr. 6
6 8 2 10 4 51 – 9 – – –
– – – 1 3 13 9 36 12 19 9
26 26 11 8 13 2 – 5 – – 10
Abbreviations: L, linoleate; O, oleate; P, palmitate; Po, palmitoleate, S, stearate; tr, trace (<0.5); HO, high oleic; HOHP, high oleic high palmitate. Adapted from Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton.
less linoleate and more oleate have enhanced oxidative stability (Table 10). Because varieties with modified fatty acid composition have been produced without genetic modification (GM), they are suitable for the current European market which is hostile to GM-crops. Like many edible oils, that from sunflower contains appreciable amounts of tocopherols (530–700 ppm – almost entirely the a-isomer) which makes both seeds and their oils good sources of vitamin E. Free sterols represent 72% of the sterol fraction (about 0.3% total oil). Sunflower deodorizer distillate contains about 5% sterols and 6% tocopherols, while the crude oil also has phosphoglycerides (0.8%) and carotenoids (1.5 ppm). Crude sunflower oil contains appreciable wax which causes a haze in unrefined oil. Sunflower seeds are often used as birdseed, in breakfast cereals and on breads. The hulls have a limited market as poultry litter and in high-fiber products. It has also been considered for biodiesel production – especially the higholeic variety. Characteristics such as viscosity, cetane number, and pour points are generally satisfactory although longerterm tests have shown a buildup of combustion chamber deposits with piston ring sticking and engine failure due to decreased fuel atomization. Overall only about 3–4% of the total sunflower oil is used for industrial purposes.
See also: Biotechnology: Acyl Lipids; Oil Deposition; Oils. Energy and Fibre Crops: Biofuels. Tropical Agriculture: Oil Palm.
Further Reading Ayorinde, F.O., 2000. Determination of the molecular distribution of triacylglycerol oils using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Lipid Technol. 12, 41–44. Barcelo-Coblijin, G., Murphy, E.J., 2009. Alpha-linolenic acid and its conversion to longer chain n-3 fatty acids: benefits for human health and a role in maintaining tissue n-3 fatty acid levels. Prog. Lipid Res. 48, 355–374. Cunnane, S.C., 2003. Problems with essential fatty acids: time for a new paradigm? Prog. Lipid Res. 42, 544–568. Green, A.G., Dribnenki, J.C.P., 1994. Linola – a new premium polyunsaturated oil. Lipid Technol. 6, 29–33. Grompone, M.A., 2005. Sunflower oil. In: Shahidi, F. (Ed.), Bailey’s Industrial Oil and Fat Products, sixth ed., vol. 2. Wiley Interscience, , New York, pp. 655–730. Gong, Y., et al., 2014. Metabolic engineering of microorganisms to produce omega-3 very long chain polyunsaturated fatty acids. Prog. Lipid Res. 56, 19–35. Guinda, A., et al., 2003. Chemical and physical properties of a sunflower oil with high levels of oleic and palmitic acids. Eur. J. Lipid Sci. Technol. 105, 130–137. Gunstone, F.D., Harwood, J.L., Dijkstra, A.J. (Eds.), 2007. The Lipid Handbook, third ed. CRC Press, Boca Raton. Gupta, M.K., 2002. Sunflower oil. In: Gunstone, F.D. (Ed.), Vegetable Oils in Food Technology – Composition, Properties and Uses. Blackwell Publishing, Oxford, pp. 128–156. Hammond, E.G., et al., 2005. Soybean oil. In: Shahidi, F. (Ed.), Bailey’s Industrial Oil and Fat Products, sixth ed., vol. 2. Wiley Interscience, New York, pp. 577–653. Kochhar, S.P., 2002. Sesame, rice-bran and flaxseed oils. In: Gunstone, F.D. (Ed.), Vegetable Oils in Food Technology – Composition, Properties and Uses. Blackwell Publishing, Oxford, pp. 297–326. Lands, B., 2014. Historical perspectives on the impact of n-3 and n-6 nutrients on health. Prog. Lipid Res. 55, 17–29. Murphy, D.J. (Ed.), 2005. Plant Lipids: Biology, Utilisation and Manipulation. Blackwell Publishing, Oxford. Salas, J.J., et al., 2014. Biochemistry of high stearic sunflower, a new source of saturated fats. Prog. Lipid Res. 55, 30–42. Thompson, L., Cunnane, S. (Eds.), 2003. Flaxseed in Human Nutrition, second ed. AOCS Press, Campaign, IL. Wolff, R.L., et al., 1998. Occurrence and distribution profiles of trans-18:1 acids in edible fats of natural origin. In: Sebedio, J.L., Christie, W.W. (Eds.), Trans Fatty Acids in Human Nutrition. The Oily Press, Dundee, pp. 1–34.
Relevant Websites http://faostat3.fao.org – FAO STAT. http://lipidlibrary.aocs.org – The Lipid Library.