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.     

Comparison of visual and automated colorimeters—An international collaborative study

Color as a fundamental quality of edible oils has been determined primarily by visual comparison methods for many decades. The automatic colorimeters introduced recently made it possible to replace the manually operated visual color instrument, which requires experience to master and is often subject to operator variabilities. A previous study with an automatic colorimeter, Colourscan, to measure the colors of refined and refined bleached cottonseed oils showed good agreement (r ²=0.99) with visual color measurements by means of the Lovibond-AOCS Color Scale. The current work is to establish a broad-scale correlation between the automated colorimeter and visual color measurements. In this international effort, factory-processed refined and refined, bleached, deodorized (RBD) canola, corn, cottonseed, peanut, sunflower and soybean oils, as well as refined palm olein, RBD palm oil, and washed, dried, filtered and deodorized tallow were used. A total of 14 laboratories from the United States and Canada, and 16 laboratories from 12 countries outside of North America, participated in this collaborative study. The results of this study, with statistical analyses, are reported.     

Depression of pour points of vegetable oils by blending with diluents used for biodegradable lubricants

Low-temperature properties need improvement before vegetable oils can receive wider recognition as biodegradable lubricants. Effects of dilution with major biodegradable fluids, namely poly alpha olefin (PAO 2), diisodecyl adipate (DIDA), and oleates, as well as impact of pour point depressant (PPD), were investigated. Since solidification of mixed unsaturated triacylglycerols is a complex thermodynamic process, the study was limited to pour point determinations. Vegetable oils demonstrated higher pour points with increased saturation and molecular weight. Cis unsaturation and hydroxy groups favored lower pour points. Dilution with oleates appeared less effective than dilution with PAO 2 and DIDA. Addition of 1% PPD (w/w) depressed pour points down to −33°C for canola and −24°C for high-oleic sunflower oils. However, neither higher amounts of PPD nor incorporation of diluent produced further depression. Depression of pour points was not proportional to the amount of diluent and ceased with further dilution. Low-temperature performance of vegetable oils limits their prospect as biodegradable lubricants, but well-balanced usage of PPD and diluents can deliver some improvements.     

Low-molecular weight organic composition of acid water from coconut oil soapstock

Soapstock from alkaline refining of coconut oil was acidified, and the resulting acid water after neutralization was subjected to gas chromatography, electron-ionization and chemical-ionization mass spectroscopy, and high-performance liquid chromatography. The chief low-molecular weight organic components were C₄−C₁₈ fatty acids, hydroxylated acids, and sugar alcohols. The prevalence of acids and total absence of phosphate compounds make coconut acid water different in composition from the acid waters from other soapstocks.     

The electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. I. Reactor design and operation

A new electrochemical method has been devised and tested for the moderate temperature/atmospheric pressure hydrogenation of edible oils, fatty acids, and fatty acid methyl esters. The method employed a solid polymer electrolyte (SPE) reactor, similar to that used in H₂/O₂ fuel cells, with water as the source of hydrogen. The key component of the reactor was a membrane-electrode-assembly, composed of a RuO₂ powder anode and either a Pt-black or Pd-black powder cathode that were hot-pressed as thin films onto the opposing surfaces of a Nafion cation-exchange membrane. During reactor operation at a constant applied current, water was back-fed to the RuO₂ anode, where it was oxidized electrochemically to O₂ and H⁺. Protons migrated through the Nafion membrane under the influence of the applied electric field and contacted the Pt or Pd cathode, where they were reduced to atomic and molecular hydrogen. Oil was circulated past the back side of the cathode and unsaturated triglycerides reacted with the electrogenerated hydrogen species. The SPE reactor was operated successfully at a constant applied current density of 0.10 A/cm² and a temperature between 50 and 80°C with soybean, canola, and cottonseed oils and with mixtures of fatty acids and fatty acid methyl esters. Reaction products with iodine values in the range of 60–105 were characterized by a higher stearic acid content and a lower percentage of trans isomers than those produced in a traditional hydrogenation process.     

Kinetics of catalytic transfer hydrogenation of some vegetable oils

Catalytic transfer hydrogenation of corn, peanut, olive, soybean, and sunflower oils has been studied with aqueous sodium formate solution as hydrogen donor and palladium on carbon as catalyst. Kinetic constants and selectivity have been determined under intensive stirring in the presence of stabilizing agents. Hydrogenation reactions followed first-order kinetics with respect to fatty acids. Besides good selectivity and short reaction time, this method offers safe and easy handling. The presence of linolenic acid retards the migration of double bonds, which explains why soybean oil is the most appropriate for this hydrogenation process.     

A comparison of high-performance liquid chromatography and spectrophotometry to measure chlorophyll in canola seed and oil

There are several methods available to measure chlorophyll in canola oil and seed, and these will not necessarily yield the same results and should not be used in terchangeably. Total chlorophyll was determined for samples of canola seed and commercial canola oil by recognized spectrophotometric methods and by high-performance liquid chromatography (HPLC). The HPLC method, which summed all chlorophyll-related pigments detected, found approximately 1.4 times more total chlorophyll per sample than did the spectrophotometric methods. The spectrophotometric methods are calibrated with only chlorophyll a and underestimate other chlorophyll pigments, which have lower extinction, coefficients and different absorption maxima. The HPLC method detects each pigment at its absorption maxima and applies the appropriate absorptivity factor. Care must be taken when comparing results obtained by different methods. There appears to be a need for a standardized method of chlorophyll pigment measurement by HPLC.     

Oxidation of phytosterols in a test food system

The oxidative stability of phytosterols in canola, coconut, peanut, and soybean oils was examined under simulated frying conditions of 100, 150, and 180°C for 20 h. The degree of oxidative decomposition was assessed by the loss of phytosterols, accumulation of phytosterol oxides, and the change in fatty acid profiles. The phytosterol oxides produced in the oils were identified using mass spectroscopy. Oils with higher levels of polyunsaturated fatty acids showed greater amounts of sterol loss; however, the sterol loss was less complete than in the more saturated oils. A greater variety of sterol oxides was observed at the lower temperatures of 100 and 150°C compared to 180°C. This study demonstrates that under conditions similar to frying, there is a loss of phytosterols and polyunsaturated fatty acids. The accumulation of phytosterol oxides may be temperature-limited because of further break-down into products not measurable by typical gas chromatography-mass spectrometry techniques.     

A novel technique for the preparation of secondary fatty amides

A technique for the synthesis of monosubstituted fatty amides at low temperature and ambient pressure was developed. This method involved the condensation of an amine with a triacylglycerol. The primary amine (ethyl,n-butyl,n-hexyl andn-octyl were tested) acted as reagent and solvent for the fatty substrates. No additional organic solvent or catalyst was added. Tallow, vegetable oils and fish oil all served well as substrates, as did pure tripalmitin. The rate of amidation was dependent upon temperature and the ratio of fat to amine. In a series of experiments conducted with tallow andn-butylamine at a fat:amine molar ratio of 1:16, amidation could be carried out at 20°C, producingn-butyltallowamide in 83% yield in 24 hr. When the fat:amine molar ratio was reduced to 1:8, and the temperature raised to 45°C, the amide yield was 87.6% in 24 hr. When the reaction was carried out at the boiling point ofn-butylamine (78°C) and at a fat:amine ratio of 1:8, the amide yield was 93.2% in 4 hr. The reaction progressed more rapidly with higher molecular weight amines. The identity and purity of the amides was assessed by thin-layer chromatography and confirmed by elemental analyses and infrared and C¹³ nuclear magnetic resonance spectroscopy.     

trans-Polyunsaturated fatty acids in French edible rapeseed and soybean oils

The fatty acid compositions of rapeseed and soybean oils marketed in France have been determined by gas liquid chromatography on a fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary phase. Under the operating conditions employed, methyl esters of linolenic acid geometrical isomers could be separated and quantitated easily without any other complementary technique. With only one exception, all samples under study (eight salad oils and five food samples) contain geometrical isomers of linolenic acid in measurable, although variable, amounts. Totaltrans-18:3 acids may account for up to 3% of total fatty acids. This value corresponds to a degree of isomerization (percentage oftrans isomers relative to total octadecatrienoic acids) of 30%. Examination of our data indicates that the distribution pattern of linolenic acid geometrical isomers does not depend on the degree of isomerization. The two main isomers always have thec,c,t and thet,c,c configurations. These isomers occur in the almost invariable relative proportions of 47.8±1.7% and 41.1±1.0%, respectively. The third mono-trans isomer is present in lower amounts−6.5±0.7%. The only di-trans isomer that can be quantitated with sufficient accuracy is thet,c,t isomer (4.9±1.5%). Mono-trans isomers of linoleic acid are also present in these oils. However, their maximum percentages are lower than those determined for linolenic acid geometrical isomers. In the oils showing the highest degrees of isomerization,trans isomers of linoleic acid account for 0.5% (rapeseed oils) and 1% (soybean oils) of total fatty acids. Taking into account all data, it would appear that the probability of isomerization of linolenic acid is about 13–14 times that of linoleic acid.     

Raffinose content may influence cottonseed susceptibility to aflatoxin contamination

The effect of the cotton storage trisaccharide raffinose and cottonseed storage protein (CSP) in combination on aflatoxin production by Aspergillus flavus was investigated. The ability of ground whole cottonseed and water-extracted cottonseed meal to support fungal biosynthesis of aflatoxin also was assessed in vitro. Dose response data showed that utilization of raffinose as a sole carbon source supported growth and aflatoxin production by A. flavus. When raffinose was a carbon source and CSP was the sole nitrogen source, aflatoxin levels were stimulated up to fourfold above those in raffinose reference media. Results with ground whole cottonseed as a sole carbon/nitrogen source demonstrated the capacity for aflatoxin production in A. flavus cultures. Lipid extraction of ground whole seed severely reduced aflatoxigenesis potential; however, lipid extraction followed by water extraction of ground whole seed restored much of the aflatoxin biosynthetic potential, suggesting the presence of a water soluble inhibitory factor. Accessible carbon appeared to be the limiting resource in water-extracted meal, as a raffinose supplement stimulated aflatoxin production. Either cottonseed storage lipid or raffinose was capable of providing accessible carbon to A. flavus. Raffinose and CSP in developing and mature cottonseed may predispose seed to potentially high levels of aflatoxin contamination by A. flavus upon seed infection.     

Comparison of the composition and properties of canola and sunflower oil sediments with canola seed hull lipids

The phase transition behavior and chemical composition of sediments from Canadian and Australian canola oils, as well as from sunflower oil, were studied by differential scanning calorimetry, X-ray diffraction, polarized-light microscopy, and chromatographic techniques. Australian canola sediment was similar to Canadian canola sediment in both melting and crystallization behaviors and chemical composition. Compared to canola sediment, sunflower sediment underwent phase transformation (melting and crystallization) at lower temperatures, and the enthalpies associated with the phase changes were greater. The X-ray diffraction patterns for these materials were similar, indicating identical crystalline structures. Sunflower sediment contained mainly wax esters (99%), while canola sediment contained about 72–74% of waxes. Moreover, sunflower sediment consisted of shorter-chainlength fatty acids and alcohols than canola sediment. A hexane-insoluble fraction from Canadian canola hull lipids had fatty acid and alcohol profiles and X-ray diffraction pattern similar to the corresponding oil sediment.     

Salinity-Induced Variation in Biochemical Markers Provides Insight into the Mechanisms of Salt Tolerance in Common (Phaseolus vulgaris) and Runner (P. coccineus) Beans

The evaluation of biochemical markers is important for the understanding of the mechanisms of tolerance to salinity of Phaseolus beans. We have evaluated several growth parameters in young plants of three Phaseolus vulgaris cultivars subjected to four salinity levels (0, 50, 100, and 150 mM NaCl); one cultivar of P. coccineus, a closely related species reported as more salt tolerant than common bean, was included as external reference. Biochemical parameters evaluated in leaves of young plants included the concentrations of ions (Na⁺, K⁺, and Cl⁻), osmolytes (proline, glycine betaine, and total soluble sugars), and individual soluble carbohydrates. Considerable differences were found among cultivars, salinity levels, and in their interaction for most traits. In general, the linear component of the salinity factor for the growth parameters and biochemical markers was the most important. Large differences in the salinity response were found, with P. vulgaris cultivars “The Prince” and “Maxidor” being, respectively, the most susceptible and tolerant ones. Our results support that salt stress tolerance in beans is mostly based on restriction of Na⁺ (and, to a lesser extent, also of Cl⁻) transport to shoots, and on the accumulation of myo-inositol for osmotic adjustment. These responses to stress during vegetative growth appear to be more efficient in the tolerant P. vulgaris cultivar “Maxidor”. Proline accumulation is a reliable marker of the level of salt stress affecting Phaseolus plants, but does not seem to be directly related to stress tolerance mechanisms. These results provide useful information on the responses to salinity of Phaseolus.     

Assessment of olive oil adulteration by reversed-phase high-performance liquid chromatography/amperometric detection of tocopherols and tocotrienols

A method involving reversed-phase high-performance liquid chromatography with amperometric detection has been developed for the analysis of tocopherols and tocotrienols in vegetable oils. The sample preparation avoids saponification. Recoveries of α-tocotrienol and γ-tocotrienol in extra virgin olive oil were 97.0 and 102.0%, respectively. No tocotrienols were detected in olive, hazelnut, sunflower, and soybean oils, whether virgin or refined. However, relatively high levels of tocotrienols were found in palm and grapeseed oils. This method could detect small quantities (1–2%) of palm and grapeseed oils in olive oil or in any tocotrienol-free vegetable oil and might, therefore, help assess authenticity of vegetable oils.     

Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

不同植物油脂在近临界水中水解反应动力学的比较

系统地测定了压力10 MPa、温度170℃～240℃范围内橄榄油、花生油、大豆油、红花油等植物油脂在近临界水中无催化水解反应动力学数据。实验结果表明,近临界水中油脂水解反应是一个典型的自催化反应,采用二级自催化反应动力学模型对动力学数据进行了拟合,得到了橄榄油、花生油、大豆油、红花油等四种植物油脂的水解反应活化能分别为41.8 kJ/mol、37.3 kJ/mol、37.7 kJ/mol、31.2 kJ/mol。油脂水解活化能与其碘价密切相关,随着油脂碘价的增加,水解活化能逐渐降低。     

Effect of baicalein and acetone extract of Scutellaria baicalensis on canola oil oxidation

There is an increasing interest in natural antioxidants present in traditional Chinese herbal medicines. The present study examined the antioxidant activity of heane, acetone, and methanol extracts, as well as baicalein purified from the dry roots of Scutellaria baicalensis Georgi (common name: Huangqin), in heated canola oil. Oxygen consumption and decreases in linoleic acid linolenic acid content were monitored in canola oil held at 90–93°C. Among the three extracts, the acetone extract was most effective against oxidation of canola oil, followed by the methanol extract of the dry roots. The antioxidant activity of these three extracts correlated well with their content of baicalein, which provided strong protection to canola oil from oxidation. The antioxidant activity of Huangqin acetone extract was dose-dependent. The acetone extract at 100 ppm or above was even more effective than butylated hydroxytoluene at 200 ppm in protecting canola oil from oxidation. The present results suggest that the acetone extract of these roots should be further explored as a potential source of natural antioxidants for use in the processed foods.     

Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

Further studies on artificial geometrical isomers of α-linolenic acid in edible linolenic acid-containing oils

Fifteen samples of commercial edible soybean and rapeseed oils (and mixtures of these) from Belgium, Great Britain and Germany have been analyzed for theirtrans-polyunsaturated fatty acid content. Only one sample out of the 13 refined samples, and the two cold-pressed samples, contained trace amounts oftrans isomers. Others contained between 1 and 3.3% of their total fatty acids as geometrical isomers of linoleic and linolenic acids. The degree of isomerization (DI) of linolenic acid varied between 10.5 and 26.9%. Combining results obtained in this study together with corresponding data for French oils (totalling 21 samples) indicates that the relative percentages of individual linolenic acid geometrical isomers depend on linolenic acid DI. Relationships linking these parameters could be approximated by straight lines, at least for DIs lying between 9 and 30%. Extrapolation to DI=0 suggests that the relative probabilities of isomerization of double bonds in positions 9, 12, and 15 are 41.7, 6.1 and 52.1%, respectively, at the very beginning of the isomerization reaction. At that time, the probability of a simultaneous isomerization of double bonds in positions 9 and 15 is close to zero. Thet,c,t isomer is apparently formedvia thec,c,t and thet,c,c isomers, the former being somewhat more prone to a second geometrical isomerization than the latter. The relative proportion of thec,t,c isomer is practically independent from the DI, at least between 9 and 30%, which would suggest that this isomer is an “end-product” of thecis-trans isomerization reaction.