Agricultural and genetic potentials of cruciferous oilseed crops

Oilseed crops of the Cruciferae are widely adapted and are of particular importance to countries in the northern latitudes. Cruciferous seed oils from the crops, rapeseed, mustard, Camelina, oilseed radish and Crambe, enter edible or industrial markets, or both. The oil-seed meal can be used either as a high protein feed supplement or as an organic fertilizer. The spring and winter forms of the two species of rapeseed,Brassica napus andB. campestris, are commercially the most important. Advances in crop management and plant breeding have resulted in a 40% to 50% increase in seed yield over the past 25 years. In the next 10 to 15 years, application of newer plant-breeding techniques will result in varieties even higher in yield and seed with improved oil and meal quality. Some of the quality improvements will be new patterns in fatty acid composition, higher oil and protein content, lower fiber content, and removal of the undesirable glucosinolate compounds from the meal. The mustard cropsBrassica juncea andB. hirta are important condiment crops which have considerable potential as edible oil sources. Oilseed radish,Raphanus sativus, yields significantly less seed and oil than other cruciferous oil crops but its oil, which contains a low level of erucic acid (3.7%) and a relatively high content of 16-carbon fatty acids (9.3%), may be useful in blending with normal or zero erucic acid rapeseed oils.Camelina sativa or false flax has many desirable agronomic characteristics but the oil of camelina seed contains too high a level of linolenic acid (36%) to penetrate the edible oil market and too low to compete industrially with linseed oil.Crambe abyssinica andC. hispanica are potentially important producers of high erucic acid industrial oils. Factors limiting Crambe development are the high cost of seed transportation due to the high volume to weight ratio of the threshed seed and the need for extra seed processing steps to render the meal suitable as a high protein feed supplement for livestock and poultry. One of 9 papers presented at the Symposium, “Cruciferous Oilseeds,” ISF-AOCS World Congress, Chicago, September 1970. Contribution No. 425, Research Station, Canada Department of Agriculture, Saskatoon, Saskatchewan, Canada.     

Composition of seeds of cruciferous oil crops

Several species of the Cruciferae family are presently used as oilseed crops, viz.,Brassica campestris (turnip rape and sarson),B. juncea (brown or yellow mustard),B. napus (rape),Crambe abyssinica (crambe), andSinapis alba (white or yellow mustard). Seed oils of these species are characterized by variable but generally large amounts of erucic acid (22:1) in the triacylglycerols, which make up 95–98% of the total lipids of high quality, viable seeds. In addition to erucic acid, the major fatty acids are oleic (typically 10–25%), linoleic (10–20%), linolenic (7–11%) and eicosenoic (5–10%). However cultivars of rapeseed lacking erucic acid and having about 55–60% oleic, 20–25% linoleic and ca. 10% linolenic acid have been developed. The eicosenoic and erucic acids are located exclusively at the 1 and 3 positions of the triacylglycerol. As a consequence, major triacylglycerol types have carbon numbers 54, 56, 58, 60 and 62. The phospholipids of rapeseed are essentially devoid of erucic acid and have palmitic, oleic and linoleic acids as major fatty acids. Sterols generally amount to about 0.5% of the oil with β-sitosterol, campesterol and brassicasterol as major constituents (about 55%, 25% and 15%, respectively, of the total sterols). A few per cent of the total sterol fractions is cholesterol. The tocopherol content of rapeseed oil is about 800 ppm with α- and γ-tocopherol as major components. Cruciferous seeds contain a fairly large number of storage proteins. Thus approximately 50 components have been detected in alkaline extracts ofBrassica napus, a major portion of which are in the molecular weight range 120–150,000. The protein spectrum ofB. napus (rape) is more complex than that ofB. campestris (turnip rape) since the former species is an allotetraploid withB. oleracea (kale, cabbage, etc.) andB. campestris as parents. Approximately 5% of the fat free seed meal is composed of glucosinolates, which are split upon enzymatic hydrolysis to antinutritional factors: isothiocyanates, oxazolidinethiones and nitriles. The different crucifers discussed have both qualitative and quantitative differences with respect to glucosinolate content. One of nine papers presented at the Symposium, “Cruciferous Oilseeds,” ISF-AOCS World Congress, Chicago, September 1970.     

The effects of original and randomized rapeseed oils containing high or very low levels of erucic acid on cardiac lipids and myocardial lesions in rats

The nutritional status of the very lowerucate rapeseed oil,Brassica napus var. ‘Tower,’ was compared with that of the high-erucate oil,Brassica napus var. ‘Target’, as well as with corn oil. The effect of randomization on the nutritional qualities of rapeseed oil was investigated as well. The feeding of diets containing the original and randomized ‘Tower” oil or the original ‘Target’ oil, at the 20% level by weight, gave growth rates which were not significantly different from that for corn oil. However, the randomized ‘Target’ oil gave growth rates which were significantly less than all other groups. The growth results could not be explained simply on the basis of food consumption. The level of triglycerides in the hearts of rats fed the very low-erucate oils was not significantly different from the corn oil group. Triglyceride concentrations in the hearts of animals given the high-erucate oils were 7–12 times greater than all other groups. The level of total fatty acids in tissue phospholipids was the same regardless of dietary treatment. Fatty acid compositions of the tissue lipids were the same in animals fed either the original or randomized rapeseed oils. A much higher incidence of focal myocardial necrosis was found in animals receiving high-erucate rapeseed oil relative to animals given the corn oil. The incidence in rats fed diets containing very low-erucate rapeseed oil was intermediate between these latter two extremes.     

Nutritional effects of partially hydrogenated low erucic rapeseed oils

The incidence of cardiac lesions in male rats fed rapeseed oil (Brassica campestris, cultivar ‘Span’) was lower with partially hydrogenated oil (iodine value 78) than with the liquid oil which had been treated in various ways. Another rapeseed oil (Brassica napus, cultivar ‘Tower’) was similarly improved when hydrogenated to iodine value 76.6, but not at iodine value 97.1, as demonstrated in both Sprague-Dawley and Wistar rats. The improved nutritional quality of hydrogenated oil appeared not to be related to the decreased concentration of linolenic acid, because that fatty acid in linseed oil with or without erucic acid did not increase the incidence of lesions. A relatively high concentration of docosahexaenoic acid in the cardiac fatty acids was observed in adversely affected groups, but a lower concentration was found with the appropriately hydrogenated rapeseed oil. Presented in part at the AOCS Meeting, Chicago, September 1976.     

Seed roasting improves the oxidative stability of canola (B. napus) and mustard (B. juncea) seed oils

Animal fats and partially hydrogenated vegetable oils (PHVO) have preferentially been used for deep‐frying of food because of their relatively high oxidative stability compared to natural vegetable oils. However, animal fats and PHVO are abundant sources of saturated fatty acids and trans fatty acids, respectively, both of which are detrimental to human health. Canola (Brassica napus) is the primary oilseed crop currently grown in Australia. Canola quality Indian mustard (Brassica juncea) is also being developed for cultivation in hot and low‐rainfall areas of the country where canola does not perform well. A major impediment to using these oils for deep‐frying is their relatively high susceptibility to oxidation, and so any processing interventions that would improve the oxidative stability would increase their prospects of use in commercial deep‐frying. The oxidative stability of both B. napus and B. juncea crude oils can be improved dramatically by roasting the seeds (165 °C, 5 min) prior to oil extraction. Roasting did not alter the fatty acid composition or the tocopherol content of the oils. The enhanced oxidative stability of the oil, solvent‐extracted from roasted seeds, is probably due to 2,6‐dimethoxy‐4‐vinylphenol produced by thermal decarboxylation of the sinapic acid naturally occurring in the canola seed.     

Canola Quality Indian Mustard Oil (<Emphasis Type="Italic">Brassica juncea</Emphasis>) is More Stable to Oxidation than Conventional Canola Oil (<Emphasis Type="Italic">Brassica napus</Emphasis>)

Canola-quality Indian mustard (Brassica juncea) is being developed as a complimentary oilseed crop to canola (Brassica napus) for cultivation in hot and low-rainfall areas, where canola does not perform well. In Australia, several B. juncea breeding lines have been developed for commercial cultivation and for eventual processing as canola oil. However, there still are significant species-based differences in the fatty acid composition with B. juncea containing lower levels of linoleic acid and higher levels of oleic and linolenic acids compared with B. napus. This has raised concern about possible oxidative stability differences between the oils. Oils (unrefined) extracted from different breeding lines of each species were subjected to accelerated autoxidation, and development of oxidative rancidity was assessed by four separate techniques: depletion of polyunsaturated fatty acids, depletion of tocopherol, development of primary oxidation products, and development of secondary oxidation products (propanal and hexanal). All the tests showed that the newly developed B. juncea oils are more stable to autoxidation than conventional canola (B. napus) oil, despite containing marginally higher linolenic levels. Oxidative stability does not appear to be a barrier to using oils from these emerging lines of B. juncea for partial or full replacement of conventional canola oil.     

Lipidchemical Investigation of Some Oilplants for Edible Oil Production Cultivated in Mongolia

Seeds of some oilplants cultivated in Mongolia (rapeseed, sunflower, soya and mustard) were investigated for oil content and fatty acid composition in dependence of their varieties and cultivation regions. Seeds of given oilplant varieties have nearly same fatty acid composition, but they differ in their oil content. The rapeseed oils do not contain erucic acid, but the seed oil of mustard contained 15.5 % eicosenoic acid.     

Versuche mit zur Produktion von Erucasäure geeigneten Kulturarten

Experiments with Oilseed Crops for the Production of Erucic Acid The Brassica-species are well suited for the production of erucic acid as industrial raw-material. The five crop species Indian mustard (Brassica juncea), Äthiopian mustard (Brassica carinata), Crambe (Crambe abyssinica), oilseed radish (Raphanus sativus ssp. oleiformis) and rocket (Eruca sativa) were tested for agricultural and seed quality characteristics. The results of the primary evaluation showed that quality is sufficient in all crops besides oilseed radish; however the starting yield level is only satisfying in Indian mustard and Crambe. It was possible to increase yields significantly in crossing progenies. As all species are summer types, their yield potential ist naturally lower than that of winter rapeseed.     

Up to 21 Different Sulfur-Heterocyclic Fatty Acids in Rapeseed and Mustard Oil

Three sulfur-heterocyclic fatty acids (SHFA) had been tentatively identified in rapeseed oil in the late 1980s. In this study we aimed to enrich and verify the presence of potential SHFA in one sample of native rapeseed oil, refined rapeseed oil and mustard seed oil. Fifty-gram samples of the three oils were individually saponified and converted into methyl esters. The resulting samples were hydrogenated and subjected three times to urea complexation. The resulting extracts of native rapeseed oil and mustard oil contained 21 different SHFA with 18, 20, 22 or 24 carbons. The refined rapeseed oil contained only nine C₁₈-SHFA. Structure investigation of the SHFA was performed by gas chromatography with mass spectrometry (GC/MS) using methyl esters and also 3-pyridylcarbinol esters. A direct screening of non-enriched samples by GC/MS in the selected ion monitoring mode and by GC with flame photometric detector (sulfur-selective) verified that the SHFA were native compounds of the oils and no artefacts of the sample preparation. Similar abundances of the four isomer groups of SHFA with monoenoic fatty acids of the same carbon number in these and five further rapeseed and mustard samples indicated that these could be the precursors of the SHFA.     

The content and composition of sterols and sterol esters in low erucic acid rapeseed (Brassica napus)

The low temperature crystallization technique for the enrichment of “minor” components, such as sterols and sterol esters, from vegetable oils was applied to low erucic acid rapeseed oils. The recovery of free sterols and sterol esters was estimated by use of¹⁴C-cholesterol and¹⁴C-cholesterol oleate. 80% of the free sterols and 45% of the sterol esters were recovered in the liquid fraction, while in two studies total recoveries were 95% and 99%, respectively. This technique showed some selectivity toward the sterol bound fatty acids when compared to direct preparative thin layer chromatography (TLC) of the crude oil. Gas liquid chromatography (GLC) analysis of the free and esterified sterols as TMS-derivatives showed very little selectivity in the enrichment procedure. The fatty acid patterns of the sterol esters demonstrated, however, a preference in the liquid fraction for those sterol esters which have a high linoleic and linolenic acid content. The content of free sterols was 0.3–0.4% and that of sterol esters 0.7–1.2% of the rapeseed oils in both winter and summer types of low erucic acid rapeseed (Brassica napus) when the lipid classes were isolated by direct preparative TLC of the oils. The free sterols in the seven cultivars or breeding lines analyzed were composed of 44–55% sitosterol, 27–36% campesterol, 17–21% brassicasterol, and a trace of cholesterol. The esterified sterols were 47–57% sitosterol, 36–44% campesterol, 6–9% brassicasterol, and traces of cholesterol and Δ5-avenasterol. The fatty acid patterns of these esters were characterized by ca. 30% oleic acid and ca. 50% linoleic acid, whereas these acids constitute 60% and 20%, respectively, of the total fatty acids in the oil. Little or no variation in sterol and sterol ester patterns with locality within Sweden was observed for the one cultivar of summer rapeseed investigated by the low temperature crystallization technique.     

Metabolism of erucic acid in perfused rat liver: Increased chain shortening after feeding partially hydrogenated marine oil and rapeseed oil

The metabolism of [14-¹⁴C] erucic acid was studied in perfused livers from rats fed on diets containing partially hydrogenated marine oil or rapeseed oil for three days or three weeks. Control rats were given groundnut oil. Chain-shortening of erucic acid, mainly to 18∶1, was found in all dietary groups. In the marine oil and rapeseed oil groups, the percentage of chain-shortened fatty acids in very low density lipoproteins-triacylglycerols (VLDL-TG) exported from the liver increased after prolonged feeding. A similar increase was found in liver TG only with partially hydrogenated marine oil. This oil, rich intrans fatty acids, thus seemed to be more effective in promoting chain-shortening. The fatty acid composition of the secreted and stored TG differed both with respect to total fatty acids and radioactively labeled fatty acids, indicating that at least 2 different pools of TG exist in the liver. The lack of lipidosis in livers from rats fed dietary oils rich in 22∶1 fatty acids is discussed in relation to these findings. In conclusion, a discussion is presented expressing the view that the reversal of the acute lipidosis in the hearts of rats fed rapeseed oil or partially hydrogenated marine oils is, to a large extent, derived from the increased chain-shortening capacity of erucic acid in liver.     

The effect of dietary partially hydrogenated marine oils on desaturation of fatty acids in rat liver microsomes

The influence of dietary partially hydrogenated marine oils on distribution of phospholipid fatty acids in rat liver microsomes was studied with particular reference to the metabolism of linoleic acid. Five groups of weanling rats were fed diets containing 20% (w/w) peanut oil (PO), partially hydrogenated peanut oil (HPO), partially hydrogenated Norwegian capelin oil (HCO), partially hydrogenated herring oil (HHO), and rapeseed oil (RSO) for 10 weeks. The partially hydrogenated oils were supplemented with linoleic acid corresponding to 4.6 cal % in the diets. Accumulation of linoleic acid and reduced amount of total linoleic acid metabolites were observed in liver microsomal phospholipids from rats fed partially hydrogenated oils as compared to PO feeding. The most striking effects on the distribution of ω6-polyunsaturated fatty acids was obtained after feeding HHO, a marine oil with a moderate content oftrans fatty acids in comparison with HPO but rich in isomers of eicosenoic and docosenoic acids. Liver microsomal Δ⁶-as well as Δ⁶-desaturase activities as measured in vitro were reduced in rats kept on HHO as compared to PO dietary treatment. The results obtained suggest that the dietary influence of partially hydrogenated marine oils on the metabolism of linoleic acid might be better related to the intake of isomeric eicosenoic and docosenoic acids than to the total intake oftrans fatty acids.     

Seed oils ofAcacia holosericea A. Cunn. ex G. Don.: Characteristics and composition

Like the fruits ofElaeis guineensis, the seeds ofAcacia holosericea have two types of oils. One is present in the yellow aril (56%), which is attached to the black seed, and the other is in the kernel of the seed (12%). The proximate composition of seed and the physicochemical characteristics of the solvent-extracted oils are reported. The aril fat is quite different from the seed oil in all respects. In descending order, the major fatty acids in aril fat are 18∶1 (54.35%), 16∶0 (29.3%), and 18∶2 (8.0%), whereas in seed (−aril) oil, the order is 18∶2 (59.45%) 18∶1 (20.2%), and 16∶0 (10.0%). In whole seed (+aril) oil, the order is 18∶2 (53.3%), 18∶1 (25%), 16∶0 (12.6).     

Edible protein products from cruciferae seed meals

Rape, crambe and mustard seed are compared with respect to properties of the fixed oil, nature of the mustard oils and properties of the seed protein. Rapeseed (Brassica campestris andB. napus) has benefited greatly from plant breeding; the erucic acid content of the fixed oil and the level of glucosinolates can now be selected. Crambe seed (Crambe abyssinica), however, is still high in erucic acid and in glucosinolates. The glucosinolate patterns of the mustards are naturally simple. Procedures for preparing edible flours and isolates from rape, crambe and mustard seed are described. With mustard (B. hirta, juncea andnigra), the glucosinolate hydrolysis products are volatile and steamstripping yields a bland flour. With rape and crambe seeds, the intact glucosinolates must be removed; aqueous extraction is practicable. The physical, chemical and nutritional properties of some of the meals, flours and isolates prepared from cruciferae seed are described. One of 9 papers presented at the Symposium, “Cruciferons Oilseeds,” ISF-AOCS World Congress, Chicago, September 1970. Contribution No. 165 from the Food Research Institute, Canada Department of Agriculture, Ottawa, Canada.     

Conifer seeds: Oil content and fatty acid composition

The seed oils from twenty-five Conifer species (from four families—Pinaceae, Cupressaceae, Taxodiaceae, and Taxaceae) have been analyzed, and their fatty acid compositions were established by capillary gas-liquid chromatography on two columns with different polarities. The oil content of the seeds varied from less than 1% up to 50%. Conifer seed oils were characterized by the presence of several Δ5-unsaturated polymethylene-interrupted polyunsaturated fatty acids (Δ5-acids) with either 18 (cis-5,cis-9, 18∶2,cis-5,cis-9,cis-12 18∶3, andcis-5,cis-9,cis-12,cis-15 18∶4 acids) or 20 carbon atoms (cis-5,cis-11 20∶2,cis-5,cis-11,cis-14, 20∶3, andcis-5,cis-11,cis-14,cis-17 20∶4 acids). Pinaceae seed oils contained 17–31% of Δ5-acids, mainly with 18 carbon atoms. The 20-carbon acids present were structurally derived from 20∶1n-9 and 20∶2n-6 acids. Pinaceae seed oils were practically devoid of 18∶3n-3 acid and did not contain either Δ5-18∶4 or Δ5-20∶4 acids. Several Pinaceae seeds had a Δ5-acid content higher than 50 mg/g of seed. The only Taxaceae seed oil studied (Taxus baccata) had a fatty acid composition related to those of Pinaceae seed oils. Cupressaceae seed oils differed from Pinaceae seed oils by the absence of Δ5-acids with 18 carbon atoms and high concentrations in 18∶3n-3 acid and in Δ5-acids with 20 carbon atoms (Δ5-20∶3 and Δ5-20∶4 acids). Δ5-18∶4 Acid was present in minute amounts. The highest level of Δ5-20∶4 acid was found inJuniperus communis seed oil, but the best source of Δ5-acids among Cupressaceae wasThuja occidentalis. Taxodiaceae seed oils had more heterogeneous fatty acid compositions, but the distribution of Δ5-acids resembled that found in Cupressaceae seed oils. Except forSciadopytis verticillata, other Taxodiaceae species are not interesting sources of Δ5-acids. The distribution profile of Δ5-acids among different Conifer families appeared to be linked to the occurrence of 18∶3n-3 acid in the seed oils.     

Carbon-13 NMR spectroscopic analysis of 24-methyl-Δ5,22-sterols in rape and mustard seed oils

24-Methylcholesta-5,E-22-dien-3β-ol (C₂₈ Δ^5,22-sterol) was separated from the unsaponifiable matters of the following eight seed oils of Brassica species:Brassica campestris (candle I and II and torch),B. napus (tower and midas),B. juncea (brown and oriental mustards), andB. alba (yellow mustard). The configuration at C-24 methyl group of the respective sterols was evaluated by¹³C NMR spectroscopy. All the C₂₈ Δ^5,22-sterols in the Brassica seed oils were found to contain the C-24 epimer of brassicasterol,trans-22-dehydrocampesterol, in the range of ca. 10–30%.     

Breeding rapeseed for oil and meal quality

Significant variation in fatty acid composition occurs within the seed oils of theBrassica genus, which includes the mustards and rapeseed. Research into the inheritance and biosynthesis of fatty acids has shown that at least two biosynthetic pathways exist in the developing rapeseed and some of the steps are under direct genetic control. The plant breeder has the basic knowledge in this oilseed crop to produce seed oils with defined fatty acid composition, and a practical example is the commercial development of Canbra oil, the rapeseed oil from which erucic acid has been eliminated.Brassica seed meals contain thioglucosides which may cause metabolic disturbances when fed to certain classes of livestock. The major thioglucosides in rapeseed meal are those giving rise to 3-butenyl and 4-pentenyl isothiocyanate and 5-vinyl-2-oxazolidinethione. Partial success in eliminating these compounds has been achieved by breeding strains of turnip rape (B. campestris) which do not contain the glucosides of 4-pentenyl isothiocyanate and oxazolidinethione, and the identification of aB. napus variety with very low levels of all three glucosides. These findings suggest that complete removal of these sulfur compounds may be possible through plant breeding. Contribution No. 309, Research Station, Canada Department of Agriculture, Saskatoon, Saskatchewan, Canada. Presented at the AOCS Meeting, Chicago, October 1967.     

γ-linolenic acid inAnemone spp. seed lipids

γ-Linolenic acid containing oils have been found in seed lipids of a number of plants, but are restricted to certain genera and families,e.g., the Boraginaceae. Some of these oils have found considerable interest for pharmaceutical and dietary use,e.g., borage oil and evening primrose oil in treatment of essential fatty acid and Δ6 desaturase deficiency. Our investigation of the seed lipids of certain Mongolian and other Ranunculaceae has now shown the presnce of unusual fatty acids, including considerable amounts (up to 20%) ofγ-linolenic acid in certain species ofAnemone, whereas this acid was found to be absent in other species ofAnemone. A number of other unusual fatty acids are present inA. rivularis but have not yet been identified. The significance of the presence ofγ-linolenic acid, a Δ6 acid, is discussed in relation to δ5 fatty acids that had been reported to occur in the same plant family.     

Chemical Properties and Fatty Acid Composition of Thunbergia fragrans Roxb. Seed Oil

The physicochemical and fatty acid compositions of seed oil extracted from Thunbergia fragrans were determined. The oil content, free fatty acids, peroxide value, saponification value and iodine value were 21.70 %, 2.25 % (as oleic acid), 9.6 (mequiv. O₂/kg), 191.71 (mg KOH/g) and 127.84 (g/100 g oil) respectively. The fatty acid profiles of the methyl esters showed the presence of 90.16 % unsaturated fatty acids and 9.84 % saturated fatty acids. Palmitoleic acid, which is usually found in marine foods and is unique in seed oils of botanical origin, was the major component (79.24 %). The oil can also be used in industries for the preparation of liquid soaps, shampoos and alkyd resin.     

Lymphatic fatty acid absorption profile during 24 hours after administration of triglycerides to rats

In this study we determined in rats the complete 24-h lymphatic fatty acid profile after administration of either rapeseed oil (RO) or rapeseed oil interesterified with 10∶0 (RO/C₁₀) with special emphasis on the transition from absorptive to postabsorptive phase. Rats were subjected to cannulation of the main mesenteric lymph duct and the next day oils were administered through a gastric feeding tube. Lymph was collected in 1-h fractions for the following 24 h. The time for maximum lymphatic transport of fatty acids was at 4 h with fast changes in fatty acid composition from the fatty acids of endogenous origin to those of the administered oils. Seven to eight hours after administration the transport was significantly lower than maximum, indicating the change from absorptive to postabsorptive phase. At 24 h after administration of either oil the transport of total fatty acids, palmitic acid (16∶0), and linoleic acid (18∶2n−6) together with oleic acid (18∶1n−9) after RO had not returned to the transport at baseline. In contrast, the transport of decanoic acid (10∶0) and α-linolenic acid (18∶3n−3) returned to baseline values between 12 and 15 h. This indicated that the absorption of purely exogenous fatty acids (illustrated by 10∶0 and 18∶3n−3) was complete at 15 h and that the fatty acids transported between 15 and 24 h were derived mostly from endogenous stores.