Roasting effects on the distribution of tocopherols and phospholipids within each structural part and section of soybeans

To clarify the effects of microwave roasting on the distribution of tocopherols and FA of phospholipids within soybeans, whole soybeans (Glycine max) were treated by microwave and further evaluted as compared to a raw sample. Tocopherol homologs, measured using HPLC, and phospholipid profiles, quantified with GC, were determined in the seed coat, the embryonic axis, and selections of cotyledons separated from three cultivars. The tocopherols were predominantly detected in the axis, followed by the cotyledons, and then very little in the coat. As much as 25% of the individual tocopherols originally present in the coat were lost at 12 min of roasting, whereas <25% was lost in the cotyledons and the axis after 20 min of roasting. The greatest rate of phospholipid loss (P<0.05) was observed in PE, followed by PC and PI, and their changing patterns were more pronounced in the coat than in the cotyledons or the axis. Thus, tocopherol content and phospholipid profiles change with microwave roasting according to tissue.     

Regional distribution in the fatty acids of triacylglycerols and phospholipids within soybean seeds (Glycine max L.)

The fatty acid distribution of triacylglycerols (TAG) and major phospholipids (PL) within soybean seeds (Glycine max L.) was investigated in relation to their tocopherol contents. The lipids extracted from four cultivars were separated by thin‐layer chromatography into seven fractions. Tocopherols were predominantly detected in the axis, followed by cotyledons and seed coat. The major lipid components were TAG and PL, while hydrocarbons, steryl esters, free fatty acids and diacylglycerols (sn‐1,3 and sn‐1,2) were also present in minor proportions. With a few exceptions, the dominant PL components were phosphatidylcholine, followed by phosphatidylethanolamine or phosphatidylinositiol. Significant differences (p <0.05) in fatty acid distribution existed when different soybean cultivars were examined. However, the principal characteristics of the fatty acid distribution in the TAG were evident among four cultivars; unsaturated fatty acids were predominantly concentrated in the sn‐2 position, and saturated fatty acids primarily occupied the sn‐1 or sn‐3 position in the oils of the soybeans.     

Tocopherol distribution and molecular species of triacylglycerols in soybean embryonic axes

Soybean embryonic axes were separated from other tissues, i.e., the cotyledons and seed coat. The molecular species and FA distribution of TAG isolated from total lipids in the embryonic axes were analyzed by a combination of argentation-TLC and GC, and were investigated in relation to their tocopherol distribution, which was determined by HPLC. The dominant components were γ-tocopherols, with much smaller amounts of α-, β-, and δ-tocopherols. A modified argentation-TLC procedure, developed to optimize the separation of the complex mixture of total TAG, provided 16 different groups of TAG, based on both the degree of unsaturation and the total acyl-chain length of FA groups. With a few exceptions, the major TAG components were S₂D (6.8–10.3%), SMD (6.9–11.2%), SD₂ (7.2–9.8%), SMT (3.2–7.4%), SDT (11.5–19.5%), D3 (3.5–8.3%), MDT (4.5–7.7%), D₂T (11.1–20.6%), and DT₂ (8.2–15.7%) (where S denotes saturated FA, M denotes monoenes, D denotes dienes, and T denotes trienes). These results indicate that there were significant differences (P<0.05) not only in tocopherol distribution but also in the molecular species of TAG among the four cultivars. Therefore, these tissues should be made available as raw materials for soybean-germ oil or soy milk, based on the differences in the distributions of tocopherol homologs and the molecular species of TAG within the embryonic axes.     

Tocopherol Content and Fatty Acid Distribution of Peas (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The positional distribution of fatty acids (FA) of triacylglycerols (TAG) and major phospholipids (PL) prepared from four cultivars of peas (Pisum sativum L.) were investigated as well as their tocopherol contents. The lipids extracted from these peas were separated by thin-layer chromatography (TLC) into seven fractions. The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while the other components were also present in minor proportions (5.6–9.2%). γ-Tocopherol was present in the highest concentration, and α- and δ-tocopherols were very small amounts. The main PL components isolated from the four cultivars were phosphatidylcholine (42.3–49.2%), followed by phosphatidylinositol (23.3–25.2%) and then phosphatidylethanolamine (17.7–20.5%). Small but significant differences (P < 0.05) in FA distribution existed when different pea cultivars were determined. However, the principal characteristics of the FA distribution in the TAG and the three PL were evident among the four cultivars; unsaturated FA were predominantly located in the sn-2 position, and saturated FA primary occupied the sn-1 or sn-3 position in the oils of the peas. These results suggest that the regional distribution of tocopherols and fatty acids in peas is not dependent on the climatic conditions and the soil characteristics of the cultivation areas during the growing season.     

A multivariate study of the correlation between tocopherol content and fatty acid composition in vegetable oils

The main biochemical function of the tocopherols is believed to be the protection of polyunsaturated fatty acids (PUFA) against peroxidation. A critical question that must be asked in reference to this is whether there is a biochemical link between the tocopherol levels and the degree of unsaturation in vegetable oils, the main source of dietary PUFA and vitamin E. We used a mathematical approach in an effort to highlight some facts that might help address this question. Literature data on the relative composition of fatty acids (16:0, 16:1, 18:0, 18:1, 18:2, and 18:3) and the contents of tocopherols (α-, β-, δ-, and γ-tocopherol) in 101 oil samples, including 14 different botanical species, were analyzed by principal-component analysis and linear regression. There was a negative correlation between α- and γ-tocopherols (r=0.633, P<0.05). Results also showed a positive correlation between linoleic acid (18:2) and α-tocopherol (r=0.549, P<0.05) and suggested a positive correlation between linolenic acid (18:3) and γ-tocopherol.     

Distribution of fatty acids during germination of soybean seeds

Gas chromatographic determination of the fatty acids in the seeds of soybean (Glycine max) showed mainly linoleic, oleic and palmitic acids with linoleic acid being the major component. Changes in the distribution of fatty acids were measured during germination in the cotyledons and roots. A decrease in palmitic and oleic acids was observed in the cotyledons from 6 to 12 days, while linoleic acid increased during the same period. In roots also, the major fatty acid was linoleic acid, while palmitic and linolenic acids were higher in roots in comparison with the cotyledons. During the 3–12 days of germination period, no major changes in the distribution pattern of fatty acids were observed in the roots. The possible significance of these changes is discussed.     

Effects of processing steps on the contents of minor compounds and oxidation of soybean oil

The processes of degumming, alkali refining, bleaching and deodorization removed 99.8% phospholipids, 90.7% iron, 100% chlorophyll, 97.3% free fatty acids and 31.8% tocopherols from crude soybean oil. The correlation coefficient between the removals of phosphorus and iron in soybean oil during processing was r = 0.99. The relative ratios of α-, β -, γ- and δ-tocopherols in crude oil, degummed oil, refined oil, bleached oil and deodorized soybean oil were almost constant, γ- and δ -tocopherols represented more than 94% of tocopherols in soybean oil. The order of oxidation stability of oil is crude > deodorized > degummed > refined > bleached oil.     

Tocopherol Content and Profile of Soybean: Genotypic Variability and Correlation Studies

Plant seed oils, including soybean seed oil, represent the major source of naturally derived tocopherols, the antioxidant molecules that act as free radical quenchers preventing lipid peroxidation in biological systems and vegetable oil products. All four isomers of tocopherols, i.e. α, β, γ, δ tocopherols that exist in nature are found in soybean seeds. The biological activity and the contribution of these isomers in improving the oxidative stability of vegetable oil are in reverse order. Because of the nutritive value and the importance for oil stability, enhancement of tocopherol content, through breeding programs, in soybean seeds has become a new and an important objective. Genotypic variability, which is the basis of every breeding program, is scarcely reported for tocopherol content and profile in soybean seeds. In the present investigation, the tocopherol content and profile in seed samples of 66 genotypes of Indian soybean were determined. The ratios observed between the lowest and the highest values for α, β, γ, δ, total tocopherol content were 1:13.6, 1:10.4, 1:7.5, 1:9.1, 1:7.9, respectively. The mean contents for α, β, γ, δ and total tocopherols were 269, 40, 855, 241 and 1,405 μg/g of oil, respectively. Total tocopherol content was the highest in ‘Co Soya2’ followed by ‘Ankur’. Concentration of α-tocopherol was the highest (27%) in ‘Ankur’ followed by ‘MACS124’ (26%) whereas gamma tocopherol concentration was the highest (69%) in ‘VLS1’ and ‘PK327’ followed by ‘MACS13’ (67%). In view of the fact that levels of unsaturated fatty acids, apart from tocopherols, also determine the oxidative stability of vegetable oils, the relationship of four isomers of tocopherols with each other as well as with different unsaturated fatty acids and oil content was also investigated in the present study. All the four isomers of tocopherols exhibited highly significant correlations with each other (p < 0.001) whereas γ-tocopherol and total tocopherol content showed a significant relationship with linoleic acid (p < 0.05).     

Effects of filtration through activated carbons on peroxide,thiobarbituric acid and carbonyl values of autoxidized soybean oil

Effects of filtration bleaching on peroxide value (PV), thiobarbituric acid value (TAV) and carbonyl value (CV) of autoxidized soybean oil were investigated by using twenty-three kinds of activated carbon in order to improve oil quality. From the decreases in PV, TAV and CV and from the physical and chemical properties of activated carbons, it was suggested that hydroperoxides, aldehydes and ketones were adsorbed on the acid sites distributed over the surface or within the pores of the activated carbons while the autoxidized soybean oil flowed through the packed column. The residual tocopherols in autoxidized soybean oil and treated soybean oil were determined during storage. The decrease in oxidative stability of treated soybean oil seemed to be caused by elimination ofα-,β-andγ-tocopherols.δ-Tocopherol was chemically more stable thanα-,β- andγ-tocopherols in autoxidized soybean oil.     

Oxidative stability of natural and randomized high-palmitic-and high-stearic-acid oils from genetically modified soybean varieties

The oxidative stability of soybean oil triacylglycerols (TAG) obtained from genetically modified soybeans was determined before and after chemical randomization. Soybean oil oxidative studies were carried out under static oxygen headspace at 60°C in the dark and oxidative deterioration was monitored by peroxide value, monometric and oligomeric oxidation products, and volatile compounds. Randomization of the soybean oil TAG improved the oxidative stability compared to the natural soybean oil TAG. Oxidative stability was improved by three factors. Factor one was the genetic modification of the fatty acid composition in which polyunsaturated acids (such as linolenic and linoleic acids) were decreased and in which monounsaturated fatty acids (such as oleic) and saturated acids (palmitic and stearic) were increased. Factor two was the TAG compositional modification with a decrease in linolenic and linoleic-containing TAG and an increase in TAG with stearic and palmitic acids in combination with oleic acid. Factor three was the TAG structure modification accomplished by an increase in saturated fatty acids and a decrease in linoleic and linolenic acids at the glycerol moiety carbon 2. Presented at the AOCS Annual Meeting & Expo, Chicago, IL, May 10–13, 1998.     

Relationship between oxidative stability of vitamin E and production of fatty acids in oils during microwave heating

Effects of microwave heating on the oxidative stability ofd-tocopherols were studied in relation to the production of fatty acids in oils. During microwave heating, the stability of tocopherols decreased in the orderδ>β>γ>α. This order did not depend on the types of ethyl esters of fatty acids or oils present. But, the shorter the chainlength and the lower the degree of unsaturation of the fatty acid ethyl esters, the greater was the reduction in amount of individual tocopherols. A similar tendency was observed when tocopherol-stripped vegetable oils, with equimolar mixtures of tocopherols added, were treated under the same conditions. The reduction in tocopherols became greater with increasing levels of free fatty acids.     

Thermoxidative stability of triacylglycerols from mutant sunflower seeds

Thermoxidative stability was evaluated in triaclyglycerols (TAG) from the oils of the mutant sunflower lines CAS-3, CAS-4, and CAS-8 (with a high percentage of stearic acid), CAS-5 (with a high percentage of palmitic acid), all from standard highlinoleic genetic backgrounds, and the mutant sunflower line CAS-12 (with a high percentage of palmitic acid), from a high-oleic genetic background. These oils contained unusually high contents of TAG molecular species with one or two saturated fatty acids at the sn-1,3 positions. Purified total TAG devoid of tocopherols were subjected to controlled thermoxidative treatment at 180°C. Polymerized TAG were determined at 2-h intervals for 10 h. After this time, total polar compounds, oxidized TAG monomers, TAG dimers, and TAG oligomers were determined. TAG from highly saturated sunflower oils with levels of linoleic acid similar to those found in conventional sunflower oils (40–50%) showed enhanced thermal stability. In these TAG, the amount of polar compounds formed during the thermoxidative treatment was similar to that formed in the high oleic acid line. Excellent results were obtained for the TAG of the CAS-12 oil, which had the highest thermal stability, producing half the amount of polar compounds as the conventional line and less than two-thirds that of the high-oleic line.     

Improvement of Oil Quality in Soybean [<Emphasis Type="Italic">Glycine max </Emphasis>(L.) Merrill] by Mutation Breeding

Low oxidative stability, off-flavor and rancidity are the major drawbacks of soybean oil. Modification of the fatty acid composition of soybean [Glycine max (L.) Merrill] oil can improve its quality and value for processors and acceptability among consumers. Mutation breeding of soybean was therefore initiated with the objective of identifying stable soybean mutants with altered fatty acid composition for improved oxidative stability and nutritional quality. Seeds of soybean cultivar ‘MACS 450’ were treated with γ-radiation and/or ethyl methane sulfonate (EMS). The harvest of M₁ plants was evaluated for fatty acid composition by gas chromatography. Highly significant variation in all the fatty acids except palmitic acid was observed. Treatment of EMS in higher concentrations as well as combined treatment of both the mutagens, i.e., γ-radiation and EMS were effective in increasing the variability for the fatty acid content in soybean oil. The variability was skewed towards high levels of oleic (35–42%) and low levels of linolenic acid (3.77–5.00%). M₃ and M₄ generations of desirable variants were analyzed for the stability of the mutated trait_. Only high oleic variants were stable in M₃ and M₄ generations. Based on fatty acid values, oxidative stability index (OSI), nutritional quality index (NQI) and ratio of essential fatty acids (ω₆/ω₃) were calculated for the control and M₂, M₃ and M₄ generations. The ω₆/ω₃ ratio in all the high oleic mutants was within the World Health Organization (WHO) recommended value (5–10%). A significant positive correlation between OSI and oleic acid content (P < 0.001) indicated improved oxidative stability of the oil while retaining nutritional quality. These high oleic lines could be utilized further in breeding programs for improvement of soybean oil quality.     

Alteration of soybean oil composition by plant breeding

Experimental lines selected from the cross PI 90406 × PI 92567 are being used in an attempt to improve soybean (Glycine max [L.] Merr.) oil by altering fatty acid composition through plant breeding. Preliminary evidence shows that the concentration of linolenic acid in soybean oil is reduced by selection for high levels of oleic acid. Levels of poly-unsaturated acids in “high oleic” selections are lower, to various degrees, but the concentration of saturated fatty acids is not different from that of the variety Dare, a representative southern commercial cultivar. In triglyceride from the “high oleic” selection, N70-3436, levels of palmitic, stearic, oleic, linoleic, and linolenic acid are 9.5, 2.0, 40.1, 43.3, and 5.1 mol %, respectively. The types of triglyceride structures observed in the experimental lines which were examined also are changed. The combined level of triolein, monooleyl-dilinolein, and dioleyl-mono-linolein in seed from N70-3436 is doubled and constitutes ca. 50% of the oil.     

Compositional and Structural Studies of the Major and Minor Components in Three Cameroonian Seed Oils by GC–MS,ESI-FTICR-MS and HPLC

The lipid components of three Cameroonian seed oils, ke tchock (Aframomum arundinaceum), njangsa (Ricinodendron heudelotii) and calabash nutmeg (Monodora myristica), have been investigated. Gas chromatography (GC)–mass spectrometry (MS) fatty acid (FA) analysis showed M. myristica seed oil to be dominated by linoleic (49.29%) and oleic (37.17%) acids; R. heudelotii was mainly linoleic (58.73%), followed by stearic (15.00%) and oleic (14.21%) acids; A. arundinaceum was predominantly oleic (65.76%) and palmitic (20.36%) acids. Electrospray ionization (ESI)-Fourier transform ion cyclotron resonance (FTICR)-MS analysis showed seven major triacylglycerol (TAG) classes for M. myristica, with C54:5, C54:4 and C54:6 dominating. R. heudelotii had eight major TAG classes with C54:8, C54:7 and C54:6 being most abundant. A. arundinaceum also had eight major TAG classes with C52:2, C54:3 and C50:2 dominating. ¹³C nuclear magnetic resonance (NMR) analysis of the TAGs showed that both sn-1,3 and sn-2 positions were predominantly occupied by linoleoyl and oleoyl chains. High-performance liquid chromatography (HPLC) fluorescence detector (FLD) analysis showed that M. myristica contained only α- and β-tocopherols (195.40 and 73.95 μg/g, respectively), R. heudelotii contained mainly γ-tocopherol (289.40 μg/g), and A. arundinaceum had mainly γ- and β-tocopherols (236.78 and 124.93 μg/g, respectively). GC–MS analysis of the unsaponifiable matter showed that β-sitosterol was the most abundant phytosterol in all three seed oils. The absolute amounts of 4-desmethylsterols were 196.15, 608.71 and 362.15 μg/g for M. myristica, R. heudelotii and A. arundinaceum seed oils, respectively. These compositional and structural studies provide justification for the use of all three seed oils in food products.     

Autoxidation of linoleic acid and behavior of its hydroperoxides with and without tocopherols

The autoxidation of linoleic acid dispersed in an aqueous media and the effect of α-, γ- and δ-tocopherols were studied. The quantitative analysis of the hydroperoxide isomers (13-cis,trans; 13-trans,trans; 9-trans,cis; 9-trans,trans) by direct high-performance liquid chromatography exhibited a prooxidant activity of α-tocopherol at high concentration (3.8% by weight of linoleic acid). On the other hand, α-tocopherol at lower concentrations (0.38 and 0.038%) and γ- and δ-tocopherols at high concentration (3.8%) were antioxidant. Furthermore, the addition of tocopherols modified the distribution of the geometrical isomers. The formation of thetrans,trans hydroperoxide isomers was completely inhibited by the highest concentration of the three tocopherols independently of their antioxidant or prooxidant activity and only delayed by the lower concentrations of α-tocopherol. The addition of tocopherols to hydroperoxide isomers reduced the decomposition rate of these isomers in the order α-tocopherol < γ-tocopherol < δ-tocopherol for thecis,trans hydroperoxide isomer and α-tocopherol ≪ γ-tocopherol ⋍ δ-tocopherol for thetrans,trans hydroperoxide isomer. With these hydroperoxides, as during linoleic acid autoxidation, α-tocopherol was completely oxidized whatever its initial concentration, while γ-tocopherol underwent partial oxidation and δ-tocopherol was practically unchanged.     

Fatty acid and triacylglycerol compositions of seed oils of five Amaranthus accessions and their comparison to other oils

This paper reports the fatty acid and triacylglycerol (TAG) compositions of five Amaranthus accessions (RRC1011, R149, A.K343, A.K432, and A. K433) representing two species and a cross between one of these and a third species. Seed oils of these were analyzed by gas chromatography and reversed-phase high-performance liquid chromatography, and their compositional properties compared with buck-wheat (Fagopyrum esculentum), corn (Zea mays), rice bran (Oryza sativa), soybean (Glycine max L. Merr.), sesame (Sesamum indicum), quinoa (Chenopodium quinoa), and cottonseed (Gossypium hirsutum) oils. All Amaranthus accessions were relatively high in palmitic (21.4–23.8%) and low in oleic (22.8–31.5%) and linolenic (0.65–0.93%) acids when compared to most of the grain and seed oils. The fatty acid composition of Amaranthus accessions K343, K433, and K432 (group I) were different from R149 and RRC1011 (group II) in mono and polyunsaturated fatty acids, but the saturate/unsaturate (S/U) ratios were very similar. All Amaranthus accessions were similar in TAG type, but showed slight differences in percentage. High similarities in UUU, UUS, and USS composition were observed among Amaranthus K343, K433 and K432, and between R149 and RRC1011. The fatty acid compositions of Amaranthus oil (group I) and cottonseed oil were similar, but their TAG compositions were different. The grain and oilseed oils were different from each other and from the Amaranthus accessions oils in terms of fatty acid composition, S/U, and TAG ratios. The UUU, UUS, and USS percentages were very diverse in grain and seed oils. The percentages of squalene in the TAG sample from the Amaranthus accessions were 8.05% in K343, 11.10% in K433, 11.19% in K432, 9.96% in R149, and 9.16% in RRC1011. Squalene was also tentatively identified in quinoa and ricebran oils at levels of 3.39 and 3.10%, respectively.     

Comparative Evaluation of Physicochemical Properties of Jatropha Seed Oil from Malaysia,Indonesia and Thailand

The jatropha oil was extracted from the jatropha seeds collected from different origins viz., Malaysia, Indonesia and Thailand. The physicochemical properties such as density, viscosity, percentage free fatty acid (FFA), iodine value, saponification value and peroxide value of the extracted jatropha seed oil were evaluated. The evaluation of fatty acid composition using gas chromatography (GC) revealed that, oleic (42.4–48.8%) and linoleic acid (28.8–34.6%) are the dominant fatty acids present in the jatropha seed oil. The saturated fatty acids such as palmitic and stearic acid lie in the range 13.25–14.5 and 7–7.7%, respectively. The observed major triacylglycerol (TAG) composition was OOL (22.94–25.75%) and OLL (15.52–20.77%).     

Tocopherol distribution and oxidative stability of oils prepared from the hypocotyl of soybeans roasted in a microwave oven

Whole soybeans (Glycin max L.) were roasted by exposure to microwaves at a frequency of 2,450 MHz, and their hypocotyls were separated from other tissues (seed coat and cotyledons). The quality characteristics and composition in the hypocotyl oils were studied in relation to their tocopherol distributions and were evaluated as compared to an unroasted oil sample. Only minor increases (P<0.05) in chemical and physical changes of the oils, such as carbonyl value, anisidine value and color development, occurred with increased roasting time. Significant decreases (P<0.05) were observed in the amounts of phospholipids in the oils after microwave roasting. Nevertheless, compared to the original level, more than 80% tocopherols still remained after 20 min of roasting. These results suggest that the exposure of soybeans to microwaves for 6 to 8 min caused no significant loss or changes in the content of tocopherols and polyunsaturated fatty acids in the hypocotyls. Therefore, a domestic microwave oven would be useful as a simple and quick means for preparing hypocotyl oil of good quality.     

Daily Intake of Cod or Salmon for 2?Weeks Decreases the 18:1n-9/18:0 Ratio and Serum Triacylglycerols in Healthy Subjects

Intake of fish and omega-3 (n-3) fatty acids is associated with a reduced concentration of plasma triacylglycerols (TAG) but the mechanisms are not fully clarified. Stearoyl-CoA desaturase-1 (SCD1) activity, governing TAG synthesis, is affected by n-3 fatty acids. Peripheral blood mononuclear cells (PBMC) display expression of genes involved in lipid metabolism. The aim of the present study was to estimate whether intake of lean and fatty fish would influence n-3 fatty acids composition in plasma phospholipids (PL), serum TAG, 18:1n-9/18:0 ratio in plasma PL, as well as PBMC gene expression of SCD1 and fatty acid synthase (FAS). Healthy males and females (n = 30), aged 20–40, consumed either 150 g of cod, salmon, or potato (control) daily for 15 days. During intervention docosahexaenoic acid (DHA, 22:6n-3) increased in the cod group (P < 0.05), while TAG concentration decreased (P < 0.05). In the salmon group both eicosapentaenoic acid (EPA, 20:5n-3) and DHA increased (P < 0.05) whereas TAG concentration and the 18:1n-9/18:0 ratio decreased (P < 0.05). Reduction of the 18:1n-9/18:0 ratio was associated with a corresponding lowering of TAG (P < 0.05) and an increase in EPA and DHA (P < 0.05). The mRNA levels of SCD1 and FAS in PBMC were not significantly altered after intake of cod or salmon when compared with the control group. In conclusion, both lean and fatty fish may lower TAG, possibly by reducing the 18:1n-9/18:0 ratio related to allosteric inhibition of SCD1 activity, rather than by influencing the synthesis of enzyme protein.