Extraction of omega‐6 fatty acids from speciality seeds

‘Omega‐6 vegetable oils’ are a small but important group of vegetable oils used widely in the food, neutraceutical, cosmetic and pharmaceutical industries for their linoleic acid (18:2 n‐6) and more importantly gamma linolenic acid (18:3 n‐6) content. These omega‐6 fatty acids have numerous health benefits recognized worldwide. With linoleic acid being readily available from many dietary sources, one wonders why there is a need to extract the oil from speciality oilseeds, however those that suffer with many of the conditions that omega‐6 fatty acids are said to be beneficial for are frequently advised to take extra supplements of these fatty acids. Due to their wide use as a nutraceutical, omega‐6 fatty acids are in high demand, causing a niche market for extraction of these oils from speciality seeds.     

Effects of nutrition labeling on edible oil processing and consumption patterns in the US

The period from 2003 to present has had a profound effect on the edible oil industry. Health/nutrition issues including trans, saturated and omega‐3 acids in the diet have impacted the soybean market, edible oil consumption patterns and consumer perception of lipid based foods. In order to satisfy the concerns, much technology has been developed to remove trans/saturated fats from the food supply. Processors have turned from hydrogenation to chemical or enzymatic modification, modified oil hardening to formulate low/zero trans products and increased use of tropical oils. Trait modified oilseeds have been developed and commercialized and are no longer niche crops supplying about 18% of domestic food oil needs.     

Einfluß der Hydrierung auf Haltbarkeit und ernährungsphysiologische Eigenschaften von Qualitätsrapsölen

Effect of Hydrogenation on Stability and Nutritional Properties of Low-Erucic Rapeseed Oils Low-erucic rapeseed oils, Lesira and Erglu, were converted to more stable edible oils by selective hydrogenation of the linolenic acid moieties while retaining most of the linoleic acid groups. Feeding Lesira oil, hydrogenated Lesira oil, soybean oil and hydrogenated soybean oil to rats did not result in any appreciable differences in growth rates, whereas feeding conventional rapeseed oil caused extensive depression of growth. Among all the groups of animals the group fed conventional rapeseed oil showed the highest weights of heart and liver. The fatty acid patterns of depot and organ lipids did not show any major difference between the groups fed hydrogenated fats and those fed the corresponding unhydrogenated oils. The fatty acid composition of the organ lipids did not reveal deficiency in essential fatty acids. In the groups fed Lesira oil and hydrogenated Lesira oil half of the animals investigated exhibited myocardial lesions of light degree, probably due to the relatively high residual level of long-chain monoenoic fatty acids, whereas in the groups fed soybean oil and hydrogenated soybean oil only one-eighth of the rats examined exhibited such effects. The occurrence and severity of these myocardial lesions are known to be much higher in rats fed conventional rapeseed oils.     

Frying stability of soybean and canola oils with modified fatty acid compositions

Pilot plant-processed samples of soybean and canola (lowerucic acid rapeseed) oil with fatty acid compositions modified by mutation breeding and/or hydrogenation were evaluated for frying stability. Linolenic acid contents were 6.2% for standard soybean oil, 3.7% for low-linolenic soybean oil and 0.4% for the hydrogenated low-linolenic soybean oil. The linolenic acid contents were 10.1% for standard canola oil, 1.7% for canola modified by breeding and 0.8% and 0.6% for oils modified by breeding and hydrogenation. All modified oils had significantly (P<0.05) less room odor intensity after initial heating tests at 190°C than the standard oils, as judged by a sensory panel. Panelists also judged standard oils to have significantly higher intensities for fishy, burnt, rubbery, smoky and acrid odors than the modified oils. Free fatty acids, polar compounds and foam heights during frying were significantly (P<0.05) less in the low-linolenic soy and canola oils than the corresponding unmodified oils after 5 h of frying. The flavor quality of french-fried potatoes was significantly (P<0.05) better for potatoes fried in modified oils than those fried in standard oils. The potatoes fried in standard canola oil were described by the sensory panel as fishy.     

Cardiopathogenicity of rapeseed oils and oil blends differing in erucic,linoleic, and linolenic acid content

Male Wistar rats were fed semipurified diets containing 20% fat for 25 weeks. Ten different oils or oil blends were employed, including rapeseed oils, simulated rapeseed-type oils, and modified rapeseed-type oils. Safflower, soybean, and hydrogenated coconut oils served as control oils. Histopathological examination of the cardiac tissue was conducted at the end of the study and an incidence-severity rating assigned to the lesions induced by each fat. Oils containing high levels of erucic acid (26–30%) induced the most severe cardiac necrosis, irrespective of the source of erucic acid (rapeseed oil or nasturtium oil). Increasing the linoleic: linolenic acid ratio of the high erucic oils to that of soybean oil failed to reduce necrosis, but the absence of linolenic acid from a high erucic acid oil blend resulted in a markedly reduced lesion incidence-severity rating, comparable to those obtained for low erucic acid rapessed oil and soybean oil which were similar. Lowest lesion incidence was obtained with safflower oil and hydrogenated coconut oil. We have postulated that linolenic acid plays a role in the etiology of cardiac necrosis observed when rats are fed diets containing low erucic acid rapeseed oils.     

Effect of Substitution of High Stearic Low Linolenic Acid Soybean Oil for Hydrogenated Soybean Oil on Fatty Acid Intake

High stearic, low α-linolenic acid soybean oil (HSLL) has been developed via traditional breeding to serve as a substitute for partially hydrogenated soybean oils used in food manufacturing. The purpose of this study was to estimate the impact on fatty acid intake in the United States if HSLL were substituted for partially hydrogenated soybean oils used in several food categories, including baked goods, shortenings, fried foods, and margarines. Using National Health and Nutrition Examination Survey (NHANES) data (1999–2002), baseline intakes of five fatty acids and trans fatty acids (TFA) were determined at the mean and 90th percentile of fat consumption. Then intakes of these fatty acids were determined after HSLL was substituted for 100% of the partially hydrogenated soybean oils used in these four food categories. The results show that baseline intake of stearic acid is 3.0% energy at the mean and 3.3% energy at the 90th percentile. Use of HSLL could increase stearic acid intake to about 4–5% energy. Mean intakes of TFA could decrease from 2.5 to 0.9% energy, and intake of palmitic acid would remain unchanged. Use of HSLL as a substitute for partially hydrogenated soybean oils would result in changes in the fatty acid composition of the US diet consistent with current dietary recommendations.     

Effects of Vegetable Oil Composition on Epoxidation Kinetics and Physical Properties

In this article, we investigate the role of triacylglycerol composition on the properties of epoxidized vegetable oils and the kinetics of the epoxidation process under conditions comparable to commercial epoxidation. Commodity soybean oil (24% oleic acid, 50% linoleic acid, and 7% linolenic acid), high‐oleic soybean oil (75% oleic acid, 8% linoleic acid, and 2.5% linolenic acid), and linseed oil (11% oleic acid, 15% linoleic acid, and 64% linolenic acid) were each epoxidized to various extents. Epoxidation rate, viscosity, differential calorimetry, and X‐ray diffraction data are presented for these oils and interpreted in the context of their fatty acid profile (mostly oleic, linoleic, or linolenic). While fully epoxidized soybean oil is widely commercially available and used in an increasing array of industrial applications, information relating to partially epoxidized oils and epoxidized oils of other cultivars is less well known.     

Measurement of fatty acids in whole soybeans with near infrared spectroscopy

Improvement of nutritional and/or functional properties of soybean oil by modification of soy fatty acid composition is one of the objectives of plant breeders. A major element of breeding is rapid identification and tracking of traits in seed samples. This discussion summarizes the progression of whole‐soybean fatty acid calibration developments at Iowa State University. Emphasis was placed on linolenic acid (18:3) and total saturates (16:0 + 18:0). Normal soybeans have 12–20% (of the oil) saturated fats; modified low saturate soybeans have 6–8% saturated fats. Normal soybeans have 6–12% linolenic acid; modified low linolenic soybeans have 1–3% linolenic acid. Infratec 122x/1241 and Bruins OmegaG NIRS units were calibrated to measure fatty acid levels as a percentage of total oil content, in whole soybeans. The first Infratec calibrations (in 1998) did not remain accurate as soybean genetics changed. Iterations of the calibration process yielded calibrations for total saturates and linolenic acid with standard errors of prediction (on 2005 crop samples not included in the calibration pool) of 1.0% percentage points and 0.8% points, respectively. These were sufficient to classify modified versus normal concentrations of the two fatty acids. The NIRS units could not determine the specific percentages within the classes of modified and normal soybeans.     

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.     

Low-linolenic acid soybean oil—Alternatives to frying oils

Oil was hexane-extracted from soybeans that had been modified by hybridization breeding for low-linolenic acid (18∶3) content. Extracted crude oils were processed to finished edible oils by laboratory simulations of commercial oil processing procedures. Oils from three germplasm lines N83-375 (5.5% 18∶3), N89-2009 (2.9% 18∶3) and N85-2176 (1.9% 18∶3) were compared to commercial unhydrogenated soybean salad oil with 6.2% 18∶3 and two hydrogenated soybean frying oils, HSBOI (4.1% 18∶3) and HSBOII (<0.2% 18∶3). Low-18∶3 oils produced by hybridization showed significantly lower room odor intensity scores than the commercial soybean salad oil and the commercial frying oils. The N85-2176 oil with an 18∶3 content below 2.0% showed no fishy odor after 10 h at 190°C and lower burnt and acrid odors after 20 h of use when compared to the commercial oils. Flavor quality of potatoes fried with the N85-2176 oil at 190°C after 10 and 20 h was good, and significantly better at both time periods than that of potatoes fried in the unhydrogenated oil or in the hydrogenated oils. Flavor quality scores of potatoes fried in the N89-2009 oil (2.9% 18∶3) after 10 and 20 h was good and equal to that of potatoes fried in the HSBOI oil (4.1% 18∶3). Fishy flavors, perceived with potatoes fried in the low-18∶3 oils, were significantly lower than those reported for potatoes fried in the unhydrogenated control oil, and the potatoes lacked the hydrogenated flavors of potatoes fried in hydrogenated oils. These results indicate that oils with lowered linolenic acid content produced by hybridization breeding of soybeans are potential alternatives to hydrogenated frying oils.     

Biological evaluation of hydrogenated rapeseed oil

A 91-day feeding study evaluated soybean oil, rapeseed oil, fully hydrogenated soybean oil, fully hydrogenated rapeseed oil, fully hydrogenated superglycerinated soybean oil and fully hydrogenated superglycerinated rapeseed oil at 7.5% of the diet in rats; a 16-wk feeding study evaluated soybean oil and the three rapeseed oils or fats at 15% of the diet. Each fat was fed to 40 rats as a mixture with soybean oil making up 20% of a semi-synthetic diet. No significant differences in body weight gains or diet-related pathology were seen in the 91-day study although the rats fed liquid rapeseed oil had slightly heavier hearts, kidneys and testes than the others. The rats fed the four fully hydrogenated fats ate more feed and had lower feed efficiencies than those fed oils but no differences were seen among the four hydrogenated fats. In the 16-wk feeding study, no pronounced pathology related to the diet was seen although the rats fed liquid rapeseed oil had a slightly higher incidence of histiocytic infiltration of cardiac muscle than the rats in the other groups. The female rats fed the three rapeseed oil fats gained significantly less weight and the females fed liquid rapeseed oil had enlarged hearts compared to the other groups. The absorbabilities of the six fats were measured in the 91-day study when fed as a mixture with soybean oil and as the sole source of dietary fat in a separate 15-day balance study. The four fully hydrogenated fats were poorly absorbed and the absorption of behenic acid from the two hydrogenated rapeseed oils was found to be 12% and 17% in the balance study and 8-40% in the feeding study. The adverse biological effects of unhydrogenated rapeseed oil containing erucic acid as reported in the literature do not occur with fully hydrogenated rapeseed oil. In addition, the low absorbability of the fully hydrogenated rapeseed oil is an added factor in its biological inertness.     

Effect of altered fatty acid composition on soybean oil stability

During the last 15 years, hybridization and induced mutation breeding of soybeans have been successful in producing an altered fatty acid composition in the extracted oil. The objective of those investigations was to produce a low-linolenic acid soybena oil. Crude oils extracted from the seeds of three such genotypes were processed in laboratory simulations of commercial procedures to finished deodorized oils. Analysis of the fatty acid composition of the three oils showed the linolenic acid content to be 3.3%, 4.2% and 4.8%. The stability of these finished oils was compared to that of oil from a soybean variety having a linolenic acid content of 7.7% and of a commercial hydrogenated-winterized soybean oil (3.0% linolenic acid). Test and control oils were evaluated by a trained sensory panel initially, after accelerated storage at 60 C and during use at 190 C in room tests. Peroxide values were determined at the time of sensory evaluation. Results indicated there was no significant difference in flavor stability during storage between test and control oils. There was no significant difference, between the oils, in peroxide development during accelerated storage. Compared to control oils, the test oils had improved overall room odor intensity scores and lacked the fishy odors of non-hydrogenated soybean oil and the hydrogenated odors of commercial cooking oil. Presented at the AOCS meeting in Honolulu, HI in May 1986.     

Recent Developments in Breeding Soybeans for Improved Oil Quality

Soybean breeding has traditionally focused on improving crop productivity. While this is still the main objective of soybean breeding programs, there is increased emphasis on improving the intrinsic characteristics of the seeds. Breeding goals with respect to oil quality improvement have been threefold: (1) reducing lipoxygenase activity, (2) decreasing linolenic acid concentrations in soybean oil and more recently (3) reducing the saturated fatty acid, palmitate, in soybean oil. The first two are aimed at improving oil flavor and shelf life. The third has been added as a result of medical concerns about excess saturated fats in the human diet. Considerable progress has been made toward achieving all three objectives. Improved soybean germplasm has been released and is being used to develop high yielding cultivars improved oil quality. Null alleles for three lipoxygenase isozymes have been transferred into the cultivar ‘Century’ through backcrossing. Three different germplasm sources have been developed through mutagenesis and selection with low concentrations of linolenic acid (3.0 to 3.5%). This material has been released and is being widely used by public and private breeders to incorporate the low linolenic acid trait into high yielding cultivars. Cultivars with 2% germplasm with lower concentrations of palmitic acid in soybean oil by as much as 50%. In the U.S., soybean oil accounts for about 50% of the palmitic acid in diets. Therefore, reducing palmitic acid in soybean oil could significantly decrease saturated fat consumption without dietary change. Other research in progress includes studies of the genetic inheritance and control oil quality traits and efforts to use molecular genetics to improve oil quality.     

Performance evaluation of hexane-extracted oils from genetically modified soybeans

Soybeans produced by induced mutation breeding and hybridization were cracked, flaked and hexane-extracted, and the recovered crude oils were processed to finished edible oils by laboratory simulations of commercial oil-processing procedures. Three lines yielded oils containing 1.7, 1.9 and 2.5% linolenic acid. These low-linolenic acid oils were evaluated along with oil extracted from the cultivar Hardin, grown at the same time and location, and they were processed at the same time. The oil from Hardin contained 6.5% linolenic acid. Low-linolenic acid oils showed improved flavor stability in accelerated storage tests after 8 d in the dark at 60°C and after 8h at 7500 lux at 30°C, conditions generally considered in stress testing. Room odor testing indicated that the low-linolenic oils showed significantly lower fishy odor after 1 h at 190°C and lower acrid/pungent odor after 5 h. Potatoes were fried in the oils at 190°C after 5, 10 and 15 h of use. Overall flavor quality of the potatoes fried in the low-linolenic oils was good and significantly better after all time periods than that of potatoes fried in the standard oil. No fishy flavors were perceived with potatoes fried in the low-linolenic oils. Total volatile and polar compound content of all heated oils increased with frying hours, with no significant differences observed. After 15 h of frying, the free fatty acid content in all oils remained below 0.3%. Lowering the linolenic acid content of soybean oil by breeding was particularly beneficial for improved oil quality during cooking and frying. Flavor quality of fried foods was enhanced with these low-linolenic acid oils.     

Essential fatty acid-deficient rats: I. Growth and testes development

Partially hydrogenated oils as the sole dietary fat enhances the development of essential fatty acid (EFA) deficiency in young rats. Partially hydrogenated herring oil (HHO) caused total impairment of the spermatogenic tissue after five weeks of experiment, while partially hydrogenated arachis oil (HAO) caused severe degeneration of this tissue in 15 weeks. A fat-free diet caused degeneration in 26 weeks. In the dietary fats, the total content oftrans acids, calculated as elaidic acid, was 47% and 23% in HAO and HHO, respectively. Further, varying amounts of different positional isomeric fatty acids were also present in the partially hydrogenated oils. Besides the specific tissue changes, poor growth, poor feed efficiency and skin signs characteristic of EFA deficiency were noticed. On the other hand, partially hydrogenated soybean oil (HSO) as the sole dietary fat kept the animals normal in all respects. this oil still contained 32% linoleic acid; the total content oftrans acids amounted to 11%, calculated as elaidic acid.     

Performance of Regular and Modified Canola and Soybean Oils in Rotational Frying

Canola and soybean oils both regular and with modified fatty acid compositions by genetic modifications and hydrogenation were compared for frying performance. The frying was conducted at 185 ± 5 °C for up to 12 days where French fries, battered chicken and fish sticks were fried in succession. Modified canola oils, with reduced levels of linolenic acid, accumulated significantly lower amounts of polar components compared to the other tested oils. Canola oils generally displayed lower amounts of oligomers in their polar fraction. Higher rates of free fatty acids formation were observed for the hydrogenated oils compared to the other oils, with canola frying shortening showing the highest amount at the end of the frying period. The half-life of tocopherols for both regular and modified soybean oils was 1–2 days compared to 6 days observed for high-oleic low-linolenic canola oil. The highest anisidine values were observed for soybean oil with the maximum reached on the 10th day of frying. Canola and soybean frying shortenings exhibited a faster rate of color formation at any of the frying times. The high-oleic low-linolenic canola oil exhibited the greatest frying stability as assessed by polar components, oligomers and non-volatile carbonyl components formation. Moreover, food fried in the high-oleic low-linolenic canola oil obtained the best scores in the sensory acceptance assessment.     

Influence of partially hydrogenated vegetable and marine oils on lipid metabolism in rat liver and heart

Partially hydrogenated marine oils containing 18∶1-, 20∶1- and 22∶1-isomers and partially hydrogenated peanut oil containing 18∶1-isomers were fed as 24–28 wt % of the diet with or without supplement of linoleic acid. Reference groups were fed peanut, soybean, or rapeseed oils with low or high erucic acid content. Dietary monoene isomers reduced the conversion of linoleic acid into arachidonic acid and the deposition of the latter in liver and heart phosphatidylcholine. This effect was more pronounced for the partially hydrogenated marine oils than for the partially hydrogenated peanut oil. The content oftrans fatty acids in liver phospholipids was similar in groups fed partially hydrogenated fats. The distribution of various phospholipids in heart and liver was unaffected by the dietary fat. The decrease in deposition of arachidonic acid in rats fed partially hydrogenated marine oils was shown in vitro to be a consequence of lower Δ6-desaturase activity rather than an increase in the peroxisomal β-oxidation of arachidonic acid. The lower amounts of arachidonic acid deposited may be a result of competition in the Δ6-desaturation not only from the C22-and C20-monoenoic fatty acids originally present in the partially hydrogenated marine oil, but also from C18- and C16-monoenes produced by peroxisomal β-oxidation of the long-chain fatty acids. Part of this work was presented at the ISF-AOCS Congress, New York City, 1980.     

Effects of fresh and used hydrogenated soybean oil on reproduction and teratology in rats

Groups of 25 pairs of two generations of male and female rats were fed diets containing 15% of either fresh hydrogenated soybean oil (iodine value, 107), a similar fat used 56 hr for deep frying or an unhydrogenated mixture of fats and oils with a fatty acid composition similar to the hydrogenated soybean oil. The first two litters of each generation were permitted to be born naturally. During the third pregnancy of each generation, one-half of the females were sacrificed on day 13 of gestation and inspected for early embryonic death. The remaining females were sacrificed on day 21 of gestation, and the fetuses were examined for either skeletal or softtissue abnormalities. There was no evidence of any deleterious effects on the reproductive parameters nor any teratogenic effects due to either hydrogenated soybean oil, a similar oil used for frying foods for 56 hr or an unhydrogenated mixture of fats and oils.     

Effects of fresh and used hydrogenated soybean oil on reproduction and teratology in rats

Groups of 25 pairs of two generations of male and female rats were fed diets containing 15% of either fresh hydrogenated soybean oil (iodine value, 107), a similar fat used 56 hr for deep frying or an unhydrogenated mixture of fats and oils with a fatty acid composition similar to the hydrogenated soybean oil. The first two litters of each generation were permitted to be born naturally. During the third pregnancy of each generation, one-half of the females were sacrificed on day 13 of gestation and inspected for early embryonic death. The remaining females were sacrificed on day 21 of gestation, and the fetuses were examined for either skeletal or softtissue abnormalities. There was no evidence of any deleterious effects on the reproductive parameters nor any teratogenic effects due to either hydrogenated soybean oil, a similar oil used for frying foods for 56 hr or an unhydrogenated mixture of fats and oils.     

Crystallisation and melting behaviour of palm kernel oil and related products by differential scanning calorimetry

Lauric oils are valuable sources for oils suitable for various food applications. They are particularly useful as cocoa butter substitutes for which steep solid fat content profiles are required. Palm kernel oil is one such fat, which upon fractionation and/or hydro‐genation provides a variety of oil fractions with different oil composition and properties. The stearins have excellent properties for confectionery fats, while the oleins can be further hydrogenated to improve their properties. This paper gives an overview of the properties of products of palm kernel oil, produced from fractionation and hydrogena‐tion. The melting and crystallisation properties from differential scanning calorimetry studies are discussed in relation to the triacylglycerols of the oils.