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.     

New sources of 9-d-hydroxy-cis-12-octadecenoic acid

9-d-Hydroxy-cis-12-octadecenoic acid has been isolated from 3 seed oils of the family Apocynaceae:Holarrhena antidysenterica (73%),Nerium oleander (11%) andNerium indicum (8%). The known occurrence of this acid was previously limited to the genusStrophanthus (9–15%). A mixture of unusual tetra-acid glycerides was isolated fromN. oleander oil by thin layer chromatography. Pancreatic lipase hydrolysis of the glyceride mixture showed that 9-d-acetoxy-cis-12-octadecenoic acid is esterified exclusively at an α-glycerol position and that normal fatty acids occupy the remaining 2 glycerol positions. A portion of the hydroxy acid inN. indicum oil was also acetylated, however, no acetate was found in eitherH. antidysenterica orStrophanthus hispidus oils. Presented at the AOCS Meeting, San Francisco, April, 1969. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Caltha palustris L. Seed Oil. A source of four fatty acids withcis-5-unsaturation

The seed oil ofCaltha palustris L. yields two unusual polyunsaturated components, all-cis-5,11,14-eicosatrienoic acid (23%) and all-cis-5,11,14,17-eicosatetraenoic acid (1%). The C₁₈ monoene fraction (26%) is a mixture ofcis-5- andcis-9-octadecenoic acids (2∶1). The C₂₀ monoene fraction (12%) is a mixture ofcis-11- andcis-5-isomers (3∶1). No. Utiliz. Res. Dev. Div., ARS, USDA.     

Hydroxy acids and estolide triglycerides ofHeliophila amplexicaulis L.f. Seed oil

Thirty percent of the fatty acids fromHeliophila amplexicaulis seed oil are hydroxy acids, primarily lesquerolic acid (14-hydroxy-cis-11-eicosenoic acid) with a trace of a new fatty acid, 16-hydroxy-cis-13-docosenoic acid. The hydroxy acids in the oil are found exclusively in the 1 and/or 3 positions of the triglycerides and are completely acylated with C₂₀ or C₂₂ saturated or monoenoic acids. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Degumming and bleaching ofLesquerella fendleri seed oil

A lesquerella species (Lesquerella fendleri) being investigated as a domestic source of seed oil containing hydroxy fatty acids shows good agronomic properties and is being tested in semi-commercial production.Lesquerella fendleri seeds contain 25% oil, of which 55% is lesquerolic acid (14-hydroxy-cis-11-eicosenoic). Oils produced in pilot-plant quantities by screw press, prepress-solvent extraction and extrusion-solvent extraction processes have been refined in the laboratory by filtering, degumming and bleaching. Two American Oil Chemists’ Society (AOCS) standard bleaching earths and two commercial earths were compared for effectiveness in bleaching these dark, yellow-red, crude lesquerella oils. Free fatty acids (1.3%), iodine value (111), peroxide value (<4 meq/kg), unsaponifiables (1.7%) and hydroxyl value (100) were not significantly affected by degumming and bleaching, but phosphorus levels of 8–85 ppm in the crude oils were reduced to 0.5–1.1 ppm in the degummed and bleached oils. Crude oils had Gardner colors of 14, which were reduced to Gardner 9–11 in the degummed and bleached oil, depending on bleach type and quantity used. AOCS colors in the range of 21–25R 68–71Y were obtained. By including charcoal in the bleaching step, a considerably lighter oil could be obtained (Gardner 7).     

Boron trifluoride as catalyst to prepare methyl esters from oils containing unusual acyl groups

The procedure of Metcalfe et al. (3) for the preparation of fatty acid methyl esters, using boron trifluoride as catalyst, is shown to be suitable for use with oils containing fatty acids of unusual structures, such as conjugated unsaturation, hydroxyl or epoxy groups, and cyclopropenes in addition to oils with only the common acids. In some cases, boron trifluoride was less destructive to unusual groups than conventional mineral acid catalysts; in others, derivatives were formed that were suitable for quantitation in subsequent gas chromatographic analysis. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Unusual olefinic fatty acids in seed oils from two genera in the ranunculaceae

Oil from one of the two species ofAnemone investigated contained 20% of γ-linolenic acid but the other had none. Linoleic acid was the major component in both oils. Four of the five species ofRanunculus produced oil containing 2% to 4% of a component identified in one sample ascis-7,cis-10-hexadecadienoic acid. Major components were linoleic and linolenic acids. No. Utiliz. Res. Dev. Div., ARS, USDA     

Gas chromatography-mass spectrometry of methyl esters of unsaturated oxygenated fatty acids

Silylation of hydroxyl groups in methyl esters of unsaturated hydroxy acids provides compounds that give mass spectra which can be readily interpreted, whereas spectra of underivatized esters are extremely difficult to evaluate. The relationship of the double bond(s) to the trimethylsiloxy (TMS) group results in specific mass spectral patterns. In esters that have the TMS group separated from the double bond by one methylene group, the ions caused byα-cleavage at the TMS group on the side closest to the olefinic group are much more abundant than those produced fromα-cleavage on the other side of the TMS group. In esters that have the TMS group and the double bond separated by two methylene groups,α-cleavage ions are approximately equal. When the TMS group and the double bond are allylic, no fragmentation results between them. Cleavage does occur on either side of this system, and those ions resulting from cleavage alpha to the TMS group are in greatest abundance. Silylation of esters that have a conjugated diene or ene-yne system adjacent to a hydroxyl group also gives derivatives amenable to gas chromatographymass spectrometry. In these esters, large peaks are observed that arise fromα-cleavage at the TMS group and at the other end of the olefinic system. No fragmentation between the TMS group and the sites of unsaturation occurs. Unsaturated epoxy methyl esters produce spectra difficult to interpret. When the epoxide is converted to methoxy-hydroxy derivatives by BF₃-methanol, the spectrum locates the position of the epoxide group. Silylation of the hydroxyl group produces a compound that gives a less complicated spectrum which also locates the original epoxy group. Mass spectrometry of a series of unsaturated keto-esters, without derivatization, provides spectra that are easily interpretable. Presented at the AOCS Meeting, Los Angeles, April 1972. N. Market. Nutr. Res. Div., ARS, USDA.     

Recovery of hydroxy fatty acids from lesquerella oil with lipases

Two hydroxy acids, lesquerolic (53 wt%) and auricolic (4%), are present at significant quantities inLesquerella fendleri seed oil. Results reported here indicate the selective release of hydroxy fatty acids during hydrolysis of this oil catalyzed byRhizopus arrhizus lipase. For example, hydroxy acids composed 85–90 wt% of the free fatty acids released during lipolysis, as compared to 54% present overall in the oil. In addition, over 80% of the lesquerolic acid is released from the triglycerides. The reason for this lipase’s success was determined to be its 1,3-positional specificity. The vast majority of lesquerella oil’s hydroxy acids is at the 1- and 3-positions of its triglycerides, as confirmed by the compositional analysis of partial glycerides formed during lipolysis.     

Effect of temperature on soybean seed constituents: Oil,protein, moisture,fatty acids,amino acids and sugars

Soybean plants were grown at day/night temperatures of 24/19 C until the beginning of seed development, and then transferred to 5 different temperature regimes (18/13, 24/19, 27/22, 30/25 and 33/28 C) in the CSIRO phytotron. Mature seeds that developed under these conditions were analyzed for variances in composition. Fatty acid composition was strongly affected by temperature: linolenic and linoleic acids decreased markedly whereas oleic acid increased as the temperature increased; palmitic and stearic acids remained unchanged. Oil content was positively correlated with temperature, and protein content increased at the highest temperature. Of the sugars analyzed, sucrose concentration decreased by 56% with a 15 C increase in temperature, and stachyose showed a slight reduction; other sugars remained unchanged. Amino acid composition was generally stable; however, methionine increased with increased temperature during seed development. Moisture content was unaffected.