Structuring of edible oils by long-chain FA,fatty alcohols,and their mixtures

Homologous series of fatty alcohols and FA with chain lengths ranging from 16 to 22 carbons were evaluated for their oil-structuring potential by texture profile analysis (TPA). FA, fatty alcohols, and their mixtures were found to structure sunflower oil and several vegetable oils at levels as low as 2% (w/w) for the pure ingredients. Mixtures of fatty alcohols and FA with the same chain lengths, at 5% (w/w) in sunflower oil, showed a synergistic effect below 20°C at the composition ratios of 7∶3 and 3∶7 (w/w). This synergistic effect in the 7∶3 stearyl alcohol/stearic acid mixture was due to effects on the microstructure of the composite material. The larger number of small crystals observed in the mixture was attributed to effects on the crystallization kinetics as a result of minimal interfacial tension at the specific 1∶3 and 3∶1 molecular ratios.     

Characterization of cold-pressed onion, parsley, cardamom, mullein, roasted pumpkin, and milk thistle seed oils

Cold-pressed onion, parsley, cardamom, mullein, roasted pumpkin, and milk thistle seed oils were characterized for their fatty acid (FA) composition, tocopherol content, carotenoid profile, total phenolic content (TPC), oxidative stability index (OSI), color, physical properties, and radical-scavenging capacities against peroxyl (oxygen radical-scavenging capacity) and stable DPPH (diphenylpicrylhydrazyl) radicals. Parsley seed oil had the highest oleic acid content, 81 g/100 g total FA, and the lowest saturated fat among the tested oils. Roasted pumpkin seed oil contained the highest level of total carotenoids, zeaxanthin, β-carotene, cryptoxanthin, and lutein at 71 μmol/kg and 28.5, 6.0, 4.9, and 0.3 mg/kg oil, respectively. Onion seed oil exhibited the highest levels of α- and total tocopherols under the experimental conditions. One of the parsley seed oils exhibited the strongest DPPH scavenging capacity and the highest oxygen radical absorbance capacity (ORAC) value of 1098 μmol Trolox equiv/g oil. However, ORAC values of the tested seed oils were not necessarily correlated to their DPPH scavenging capacities under the experimental conditions. The highest TPC of 3.4 mg gallic acid equiv/g oil was detected in one of the onion seed oils. The OSI values were 13.3, 16.9–31.4, 47.8, and 61.7 h for the milk thistle, onion, mullein, and roasted pumpkin seed oils, respectively. These data suggest that these seed oils may serve as dietary sources of special FA, tocopherols, carotenoids, phenolic compounds, and natural antioxidants. An erratum to this article is available at .     

Effect of α- and γ-tocopherols on thermal polymerization of purified high-oleic sunflower triacylglycerols

The antipolymerization effects of α- and γ-tocopherols were compared in model systems composed of purified high-oleic sunflower triacylglycerols at 180°C. γ-Tocopherol was much more effective as an antipolymerization inhibitor than α-tocopherol, partly due to lower oxidizability/disappearance. Purified triacylglycerols of sunflower, rapeseed, and high-oleic sunflower oils were less stable than their nonpurified forms containing tocopherols. Results confirmed that tocopherols per se can act as antipolymerization agents in high-oleic oils at frying temperatures. No synergism was observed when α- and γ-tocopherols were present together although larger amounts of residuals were left for both tocols. Results suggested that high-oleic/high-γ-tocopherol oils (such as high-oleic canola and high-oleic soybean oils) may provide better frying oils than high-oleic/high-α-tocopherol oils (such as high-oleic sunflower oil).     

Phospholipid class and FA compositions of modified soybeans processed with two extraction methods

Soybean lecithin is used as an emulsifier in food, cosmetic, and pharmaceutical industries. The proportion of individual phospholipids (PL) and their FA composition may affect the functional properties of lecithin. In this research, lecithins recovered from four modified soybeans and one commodity soybean, which were processed by extrusion-expelling and conventional solvent extraction, were analyzed for proportion of PL class and FA composition. HPLC with an ELSD analysis demonstrated that the percentage of PC in extrusion-expelled lecithin was higher than in solvent-extracted lecithin, whereas the PE content was lower. GC analysis showed that FA compositions of the PL varied with soybean type. The oil extraction method did not significantly affect FA composition. Critical micelle concentration tested with a tensiometer showed differences among the lecithins.     

Effects of α- and γ-tocopherols on the autooxidation of purified sunflower triacylglycerols

The antioxidant effects of α- and γ-tocopherols were evaluated in a model system based on the autooxidation of purified sunflower oil (p-SFO) triacylglycerols at 55°C for 7 d. Both tocopherols were found to cause more than 90% reduction in peroxide value when present at concentrations >20 ppm. α-Tocopherol was a better antioxidant than γ-tocopherol at concentrations ≤40 ppm but a worse antioxidant at concentrations >200 ppm. Neither α- nor γ-tocopherol showed a prooxidant effect at concentrations as high as 2000 ppm. The amount of tocopherols consumed during the course of oxidation was positively correlated to the initial concentration of tocopherols, and the correlation was stronger for α- than for γ-tocopherol. This correlation suggested that, besides reactions with peroxyl radicals, destruction of tocopherols may be attributed to unknown side reactions. Addition of FeSO₄, as a prooxidant, caused a 12% increase in the peroxide value of p-SFO in the absence of tocopherols. When tocopherols were added together with FeSO₄, some increase in peroxide value was observed for samples containing 200, 600 or 1000 ppm of α- but not γ-tocopherol. The addition of FeSO₄, however, caused an increase in the amount of α- and γ-tocopherols destroyed and led to stronger positive correlations between the amount of tocopherols destroyed during oxidation and initial concentration of tocopherols. No synergistic or antagonistic interaction was observed when α- and γ-tocopherols were added together to autooxidizing p-SFO.     

Regiospecific analysis by ethanolysis of oil with immobilized <Emphasis Type="Italic">Candida antarctica</Emphasis> lipase

A mixture of oil/ethanol (1∶3, w/w) was shaken at 30°C with 4% immobilized Candida antarctica lipase by weight of the reaction mixture. The reaction regiospecifically converted FA at the 1- and 3-positions to FA ethyl esters, and the lipase acted on C₁₄−C₂₄ FA to a similar degree. The content of 2-MAG reached a maximum after 4 h; the content was 28–29 mol% based on the total amount of FA in the reaction mixture at 59–69% ethanolysis. Only 2-MAG were present in the reaction mixture during the first 4 h, and 1(3)-MAG were detected after 7 h. After removal of ethanol from the 4-h reaction mixture by evaporation, 2-MAG were fractionated by silica gel column chromatography. The contents of FA in the 2-MAG obtained by ethanolysis of several oils coincided well with FA compositions at the 2-position, which was analyzed by Grignard degradation. It was shown that ethanolysis of oil with C. antarctica lipase can be applied to analysis of FA composition at the 2-position in TAG.     

Effect of genetic modification on the distribution of minor constituents in canola oil

Oil derived from different lines of genetically modified canola varieties was analyzed for phospholipids, tocopherols, and phytosterols by various chromatographic techniques. As observed previously in genetically modified soybean oils, there was a decrease in the content and composition of phosphatidic acid in three of the modified canola oils derived from the 12 varieties investigated. Normal-phase high-performance liquid chromatographic (HPLC) analyses showed small variations in the phospholipid content of major classes, despite few differences in their composition. Reversed-phase HPLC data indicated that the molecular species distribution of phosphatidylethanolamine was significantly altered by genetic modification when compared to phosphatidylcholine. Impact of oilseed modification on the tocopherol content was variable, with greater variation in the concentration of α- and γ-tocopherols than δ-tocopherol. Phytosterol composition was markedly affected by genetic modification. Brassicasterol, campesterol, and β-sitosterol levels were consistently lowered in one genotype, whereas increased brassicasterol content was observed in the other variety. In general, genetic modification of canola seeds led to changes in the distribution of phospholipids, tocopherols, and phytosterols. Presented in part at the 89th AOCS Annual Meeting & Expo, Chicago, Illinois, May 10–13, 1998.     

Effect of saline irrigation water on olive oil composition

Virgin olive oils were obtained in Egypt from fruits of olive trees irrigated with waters of different salinity concentration (control, 1800, 3600 and 6000 ppm) during the 1992 season. The effect of water salinity on olive oil fatty acid, fatty acid location in triacylglycerol moiety, triacylglycerol, sterol and tocopherol composition was determined. Oleic acid slightly increased and linoleic decreased in the total fatty acid composition, as well as on glycerol carbon-2 and-1(3), with increased water salinity. Trioleoyl, stearoyldioleoyl and palmitoyldioleoyl glycerols are slightly increased with increased water salinity. Total tocopherol was 87.7 mg/kg in the control and increased to 147.0 mg/kg for water with 1800 ppm salinity. At higher salinity concentration, total tocopherol decreased to 107.2 and to 89.1 mg/kg for water salinities of 3600 and 6000 ppm, respectively. The same trend was observed for α, β and γ-tocopherols. Campesterol and β-sitosterol were increased with water salinity of 1800 ppm and decreased when water salinity increased further. Stigmasterol increased at water salinity of 3600 ppm and decreased sharply when the salinity was increased to 6000 ppm. These olive oil composition studies showed that although water salinity may have some compositional effects, there was no major adverse effect on fatty acid, triacylglycerol, triacylglycerol fatty acid location, sterol and tocopherol composition for oil from olives of trees grown with water with a salt composition of up to 6000 ppm.     

Genotype and Growing Environment Effects on the Tocopherols and Fatty Acids of <Emphasis Type="Italic">Brassica napus</Emphasis> and <Emphasis Type="Italic">B. juncea</Emphasis>

The effects of genotype and growing environment on the tocopherols and fatty acids (FA) of experimental Brassica juncea and B. napus breeding lines were investigated. For both species, with the exception of a few genotypes, the concentration ratio of γ-tocopherols to α-tocopherol was practically constant. The genotype influenced the tocopherol concentration in B. napus, and to a lesser degree, B. juncea. The environment also had a similar effect, and a positive correlation existed between the daily maximum temperature and the α-tocopherol concentration in B. napus. Genotype effects on the FA composition were significant for the conventional but not for Clearfield or triazine tolerant traits of B. napus. The genotype had no effect on the FA of the B. juncea genotypes. In contrast, the growing environment had a significant influence on the FA composition of both species with apparent influence from temperature and rainfall. For both species, the concentration of γ-tocopherol as well as total tocopherols was inversely related to the 18:3 concentration, which could have resulted from opposite and independent effects of temperature on the two variables. No relationship existed between the concentrations of tocopherol and the remaining unsaturated FA 18:1 and 18:2. The positional distribution of unsaturated FA within the oil triacylglycerol was a function of their total concentration.     

Composition of organic and conventionally produced sunflower seed oil

The aim of the present study was to highlight the main differences between seed oils produced from conventionally cultivated crops and organically cultivated ones and processed using mild extraction procedures. The composition and the nutritional and health aspects of both types of sunflower seed oils were compared and were analytically tested to determine the macroscopic differences in proximate composition, the main differences in the minor components, the main quality parameters, the in vitro antioxidant activity, and the presence of trans-ethylene steroisomers in FA. No significant trends were found in the oil samples for TAG and FA composition, but remarkable differences were found in the composition of minor components and in the main chemical and analytical quality properties. The organically grown samples had a higher total antioxidant activity compared with the conventional samples. Trans FA were found only in the conventional oils.     

Seasonal Variation of Chemical Composition and Antioxidant Activity of Essential Oil from <Emphasis Type="Italic">Pistacia atlantica</Emphasis> Desf. Leaves

The composition and antioxidant activities of Pistacia atlantica Desf. essential oil were investigated. Qualitative and quantitative differences in compositions and in antioxidant activities of male and female leaf essential oils were observed during the season. The essential oils obtained by hydrodistillation were analysed by GC and GC–MS. The oils were rich in monoterpenes hydrocarbons and oxygenated sesquiterpenes. The main components of male essential oil were α-pinene/α-thujene, spathulenol and bicyclogermacrene. The major component of female essential oil was δ-3-carene. The seasonal variation showed that most of the main components of the oils reached theirs highest values in September. The antioxidant activity of the oil was investigated in vitro using two assays: DPPH^· (2,2-di-phenyl-1-picrylhydrazyl) free radical-scavenging and FRAP (Ferric Reducing Antioxidant Power). The highest antioxidant capacity to scavenge free DPPH radicals was reached in the month of June for male oils and during the months of September–October for the female oils. The high reducing power for male oil was observed during the month of June and for the female oil it was in August. The female oil was more active than the male oil. The antioxidant capacity of the female oil was almost ten times higher than Ascorbic acid in the FRAP assay.     

Paradoxical effect of n−3-containing vegetable oils on long-chain n−3 fatty acids in rat heart

Flaxseed, echium, and canola oils contain α-linolenic acid (18∶3n−3, ALA) in a range of concentrations. To examine their effect on elevating cardiac levels of long-chain n−3 FA, diets based on these n−3-containing vegetable oils were fed to rats for 4 wk. Sunflower oil, which contains little ALA, was a comparator. Despite canola oil having the lowest ALA content of the three n−3-containing vegetable oils, it was the most potent for elevating DHA (22∶6n−3) levels in rat hearts and plasma. However, the relative potencies of the dietary oils for elevation of EPA (20∶5n−3) in heart and plasma followed the same rank order as their ALA content, i.e., flaxseed>echium>canola>sunflower oil. This paradox may be explained by lower ALA intake leading to decreased competition for Δ6 desaturase activity between ALA and the 24∶5n−3 FA precursor to DHA formation.     

Size and number of lymph particles measured by a particle sizer during absorption of structured oils in rats

Chylomicrons transport absorbed fat from the intestine to the circulation. During dietary fat absorption, the chylomicrons become larger in diameter, and in some studies an increase in chylomicron number has been observed as well. In the present study, we compared particle size and number in rat lymph following administration of four different oils. We administered fish oil, medium-chain TAG (MCT), and two structured oils differing in intramolecular structure, with either medium-chain FA in the outer positions of the TAG and long-chain n−3 PUFA in the sn-2 position (MLM oil) or with the reverse structure (LML oil), to lymph-cannulated rats and collected lymph in fractions for the following 8 h. Chylomicron size was measured by a particle size analyzer immediately after collection, and from these data the number of chylomicrons present was estimated. The number of particles in lymph increased during the absorption of oils containing long-chain PUFA (MLM, LML, and fish oil), whereas it was not affected by administration of MCT. The FA from MCT were probably absorbed via the portal vein; therefore, only a small number of particles were measured in lymph. When comparing the two structured oils, we observed a tendency toward a higher number of particles after LML administration, although the difference was not statistically significant. The highest number of particles after administration of all oils was observed in the size intervals 53–80 and 80–121 nm and probably represented small chylomicrons. Thus, the FA composition influenced the number of particles in lymph during absorption, whereas TAG structure had only a minor influence.     

Genetic diversity for lipid content and fatty acid profile in rice bran

Rice (Oryza sativa L.) bran contains valuable nutritional constituents, which include lipids with health benefits. A germplasm collection consisting of 204 genetically diverse rice accessions was grown under field conditions and evaluated for total oil content and fatty acid (FA) composition. Genotype effects were highly statistically significant for lipid content and FA profile (P<0.001). Environment (year) significantly affected oil content (P<0.05), as well as stearic, oleic, linoleic, and linolenic acids (all with P<0.01 or lower), but not palmitic acid. The oil content in rice bran varied relatively strongly, ranging from 17.3 to 27.4% (w/w). The major FA in bran oil were palmitic, oleic, and linoleic acids, which were in the ranges of 13.9–22.1, 35.9–49.2, and 27.3–41.0%, respectively. The ratio of saturated to unsaturated FA (S/U ratio) was highly related to the palmitic acid content (r ²=0.97). Japonica lines were characterized by a low palmitic acid content and S/U ratio, whereas Indica lines showed a high palmitic acid content and a high S/U ratio. The variation found suggests it is possible to select for both oil content and FA profile in rice bran.     

Rapid Assessment of Frying Performance Using Small Size Samples of Oils/Fats

A rapid, effective test mimicking actual frying was developed to assess the frying performance of oils and fats using small size samples. To a small volume of the oil to be tested, a formulated food consisting of gelatinized potato starch, glucose and silica gel (4:1:1 w/w) were added and content heated at 185 ± 5 °C with mixing for 2 h. Thermo-oxidative degradation of the oil was assessed by the measurement of the total amount of polar components and their composition, including degradation of tocopherols. The developed fast test accurately mimics actual frying done using an institutional fryer as assessed by the accumulation and composition of total polar components and the amount of residual tocopherols. The validity of the test was assessed using the following oils: regular canola, high oleic– low linolenic canola, and high oleic sunflower. Comparison of data between the fast frying test and institutional frying revealed a lack of significant differences. The developed frying test provides reliable quantitative and qualitative data describing the performance of the frying oil/fat. The rapid frying procedure allows assessment of the frying performance of oils at the early stages of development where usually only small amounts of the sample are available and when a large number of samples have to be tested assessing effects of oil additives.     

Oxidative and flavor stability of oil from lipoxygenase-free soybeans

Soybeans that lack or contain three lipoxygenase (LOX) isozymes, LOX-1, LOX-2, and LOX-3, were evaluated for oxidative and flavor stability at 60°C in the dark and at 35°C in the light. Although the two types of soybeans had a similar genetic background, there were significant differences (P ≤ 0.01) in fatty acid percentages between the lipoxygenase-free and normal oils before and after storage at both temperatures. The linolenic acid content of oil from LOX-free germplasm before storage averaged 7.2%, while normal lines averaged 6.6%. The linoleic acid content after storage averaged 6.9% for LOX-free and 6.6% for normal oils. LOX-free oil was not significantly different from normal oil in flavor, as judged by a sensory panel, or in concentrations of volatiles during storage at either storage condition. LOX-free oil had less hexanal than normal oil before storage, but had significantly greater (P ≤ 0.05) levels after storage for two weeks at 35°C. Peroxide values of oil from LOX-free soybeans were significantly greater (P ≤ 0.01) than oil from the normal soybean after storage at 60 and 35°C. LOX-free oil had significantly greater (P ≤ 0.01) levels of α-, β-, and γ-tocopherols. In general, oil from LOX-free soybeans did not have improved flavor or oxidative stability. Differences between the two oil types in peroxide value and in production of a few volatiles were probably a result of the differences in initial fatty acid composition.     

Oxidative and flavor stability of oil from lipoxygenase-free soybeans

Soybeans that lack or contain three lipoxygenase (LOX) isozymes, LOX-1, LOX-2, and LOX-3, were evaluated for oxidative and flavor stability at 60°C in the dark and at 35°C in the light. Although the two types of soybeans had a similar genetic background, there were significant differences (P≤0.01) in fatty acid percentages between the lipoxygenase-free and normal oils before and after storage at both temperatures. The linolenic acid content of oil from LOX-free germplasm before storage averaged 7.2%, while normal lines averaged 6.6%. The linoleic acid content after storage averaged 6.9% for LOX-free and 6.6% for normal oils. LOX-free oil was not significantly different from normal oil in flavor, as judged by a sensory panel, or in concentrations of volatiles during storage at either storage condition. LOX-free oil had less hexanal than normal oil before storage, but had significantly greater (P≤0.05) levels after storage for two weeks at 35°C. Peroxide values of oil from LOX-free soybeans were significantly greater (P≤0.01) than oil from the normal soybean after storage at 60 and 35°C. LOX-free oil had significantly greater (P≤0.01) levels of α-, β-, and γ-tocopherols. In general, oil from LOX-free soybeans did not have improved flavor or oxidative stability. Differences between the two oil types in peroxide value and in production of a few volatiles were probably a result of the differences in initial fatty acid composition.     

Camelina oil and its unusual cholesterol content

The oil in Camelina sativa L. Crantz has a combined linolenic and linoleic acid content that is greater than 50% and a relatively low saturated FA content (∼10%). Although the FA composition has been reported, no information is available on the sterol composition of camelina oil. The derivatized plant sterols were separated and quantified with capillary GC and their identity confirmed with GC-MS. The refined camelina oil sample contained approximately 0.54 wt% unsaponifiables, and over 80% of the unsaponifiables were desmethylsterols. Perhaps the most unusual characteristic of camelina oil is its relatively high content of cholesterol, particularly for a vegetable oil, since it contains several times the cholesterol found in other “high-cholesterol” vegetable oils. Camelina oil also contains relatively large amounts of another unusual sterol, brassicasterol. The major sterols identified in the camelina oil included cholesterol (188 ppm), brassicasterol (133 ppm), campesterol (893 ppm), stigmasterol (103 ppm), sitosterol (1,884 ppm), and Δ⁵-avenasterol (393 ppm).     

Antioxidant Activity of Raisin Extracts in Bulk Oil,Oil in Water Emulsion,and Sunflower Butter Model Systems

The antioxidant activities of the raisin extract (RE) in stripped corn oil, stripped corn oil emulsions, and sunflower butter stored at 60 °C for up to 15 days was evaluated. Peroxide values and hexanal content were measured on a half day, 2 or 3 day basis for the emulsion, sunflower butter, and bulk oil, respectively. The RE had the best antioxidant activity in the bulk oil system. Statistical contrasts indicated the oxidation of bulk corn oil treated with RE was significantly (p < 0.001 and p = 0.044) lower than bulk oil and bulk oil treated with tertiary-butylhydroquinone (TBHQ), respectively. No differences (p = 0.15) in hexanal concentrations were observed in stored bulk oils treated with RE and TBHQ. However, both these materials inhibited hexanal formation better (p < 0.001) when compared to the control corn oil. In contrast, 200 μg/g TBHQ had better (p = 0.0004) antioxidant activity than 3,000 μg/g RE in the oil in water(o/w) emulsion. No significant differences (p = 0.1637) in hexanal formation were observed in the emulsions treated with RE and TBHQ. However, the data indicated that the RE treated emulsion did undergo more secondary oxidation than the emulsion treated with TBHQ beyond 110 h. The 3,000 μg/g RE had antioxidant activity in sunflower butter, but was less effective than the 200 μg/g TBHQ and a lower RE concentration (200 μg/g). The observations supported the hypothesis that RE has antioxidant activity in the multiple model systems.     

Characterization and compositional studies of the oils from some legume cultivars, <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>, grown in Southern Africa

Seed oils from six legume cultivars of Phaseolus vulgaris, grown in the Kingdom of Lesotho, were extracted and their physicochemical properties and FA compositions were determined in order to compare their dietary lipids with those in P. vulgaris cultivars grown in other parts of the world. The oil content of the beans was very low, ranging from 1.5 to 2.0% (w/w). The acid values ranged from 11.0 to 19.2 mg KOH/g, whereas a combination of the PV and the p-anisidine values in Holm's equation gave oxidation values that ranged from 11.0 to 15.0. Thus, considerable enzymatic hydrolysis and oxidation had taken place in the beans during storage. Iodine values ranged from 80.5 to 92.3 (Wijs method), indicating moderate unsaturation in the oils. However, capillary GC analysis, supported by proton NMR analysis of the FAME, gave a total unsaturation range from 79.67 to 84.24%. The dominant FA were α-linolenic acid (36.47–48.81%) and linoleic acid (20.96–36.10%), with appreciable amounts of palmitic acid (14.33–18.23%). This FA composition pattern is quite similar to the FA distribution reported for low oil-bearing legume seeds. Thus, notwithstanding the different climatic and soil conditions, the general properties of lipids in the southern African legume cultivars were quite similar to those of lipids in P. vulgaris cultivars grown in other parts of the world. The high content of α-linolenic acid in the cultivars of P. vulgaris could very likely play a beneficial role in reducing the risk of coronary heart disease among the large populations consuming them in the southern African region.