Detection of adulteration of sesame and peanut oils via volatiles by GC × GC–TOF/MS coupled with principal components analysis and cluster analysis

The method of headspace coupled with comprehensive two‐dimensional GC–time‐of‐flight MS (HS‐GC × GC–TOF/MS) was applied to differentiate the volatile flavor compounds of three types of pure vegetable oils (sesame oils, peanut oils, and soybean oils) and two types of adulterated oils (sesame oils and peanut oils adulterated with soybean oils). Thirty common volatiles, 14 particular flavors and two particular flavors were identified from the three types of pure oils, from the sesame oils, and from the soybean oils, respectively. Thirty‐one potential markers (variables), which are crucial to the forming of different vegetable oil flavors, were selected from volatiles in different pure and adulterated oils, and they were analyzed using the principal component analysis (PCA) and cluster analysis (CA) approaches. The samples of three types of pure vegetable oil were completely classified using the PCA and CA. In addition, minimum adulteration levels of 5 and 10% can be differentiated in the adulteration of peanut oils and sesame oils with soybean oils, respectively. Practical applications: The objective was to develop one kind of potential differentiated method to distinguish high cost vegetable oils from lower grade and cheaper oils of poorer quality such as soybean oils. The test result in this article is satisfactory in discriminating adulterated oils from pure vegetable oils, and the test method is proved to be effective in analyzing different compounds. Furthermore, the method can also be used to detect other adulterants such as hazelnut oil and rapeseed oil. The method is an important technical support for public health against profit‐driven illegal activities.     

Wax ester fraction of edible oils: Analysis by on‐line LC‐GC‐MS and GC×GC‐FID

The wax ester fraction of various plant oils was isolated by normal‐phase HPLC (NPLC) on‐line coupled to GC via the on‐column interface and applying concurrent eluent evaporation. The esters were analyzed by on‐line NPLC‐GC‐MS and by comprehensive two‐dimensional GC with flame ionization detection (GC×GC‐FID) off‐line combined with NPLC‐GC. GC×GC‐FID enables to group the various classes of wax esters, in particular the phytol esters, geranylgeraniol esters and the straight‐chain esters of palmitic acids and the unsaturated C₁₈ acids. Optimization of the GC×GC columns and the conditions must take into account the limited thermostability of the diterpene esters. Chromatograms are shown for a range of oils, with particular focus on the various classes of wax esters in olive oil and the geranylgeraniol esters 22:0 and 24:0 in a variety of oils.     

Salting‐out of acetone, 1‐butanol,and ethanol from dilute aqueous solutions

The salting‐out phase equilibria for acetone, 1‐butanol, and ethanol (ABE) from dilute aqueous solutions using potassium carbonate (K₂CO₃) and dipotassium hydrogen phosphate trihydrate (K₂HPO₄?3H₂O) as outstanding salting‐out agents were investigated. Increasing the salt concentration strengthened the salting‐out effects and improved the distribution coefficients of all three solvents (ABE) significantly. Temperature had a slight effect on the phase equilibria. The K₂HPO₄ solution (69 wt %) showed a stronger salting‐out effect than the K₂CO₃ solution (56 wt %) on recovering ABE from dilute aqueous solutions. Dilute aqueous solutions containing more solvents increased the recoveries of acetone and 1‐butanol, while the results showed a negligible effect on the solubility of ABE. The solubility of ABE was also correlated well with the molar number of salt per gram of water in the aqueous phase. A new equation demonstrated this satisfactorily. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3470–3478, 2015     

Comprehensive two-dimensional gas chromatography with time of flight mass spectrometry applied to biomarker analysis of oils from Colombia

In order to become GC × GC-TOFMS a useful tool in geochemical oil prospecting, it is mandatory to be able to calculate quantitative geochemical parameters. A suite of Colombian oils from Upper Magdalena Valley Basin was chosen to obtaining several thermal maturity and source parameters based on biomarker ratios showing that GC × GC-TOFMS is able to be used to provide relevant geochemical information.     

Seasonal fat and fatty acids variations of seven marine fish species from the Mediterranean Sea

Seasonal variations of proximate compositions, muscle lipids and fatty acids (FA) of seven seawater species (Silllago sihoma, Upeneus pori, Sparus aurata, Saurida undosquamis, Epinephelus auneus, Mullus barbatus, Solea solea) from the Mediterranean Sea, were determined in all seasons. The results showed that the fatty acid compositions of each species ranged from 26.41 to 38.70% saturated (SFA), 13.78 to 26.52% monounsaturated (MUFAs) and 25.02 to 50.83% PUFAs. The highest proportions of EPA were obtained from M. barbatus (8.34%) in spring, S. sihoma (7.54%), U. pori (6.75%), S. aurata (6.31%), S. undosquamis (5.12%), E. auneus (5.10%) in summer, and also S. solea (6.19%) in spring. The highest proportions of DHA were found in spring, ranging from 25.14% for M. barbatus to 34.87% for S. aurata, except for S. solea (30.44%) in winter and S. sihoma (15.83%) in summer. The results showed that from a quality point of view, all species were suitable for human nutrition, since muscle lipids are rich in EPA + DHA in all seasons. Practical application : The American and Canadian Dietetic Associations recommend two servings of fatty fish per week and a daily combined intake of EPA and DHA of 500 mg. This follows a trend of numerous publications and other guidelines recognizing the health benefits of long‐chain n‐3 PUFA from fish or marine microbial sources with respect to cardiovascular health, neurological diseases, infant health and development, inflammation and cancer and other health effects. The seven species analyzed here provide muscle lipids that are rich in EPA and DHA. Only minor season‐to‐season changes in the total content of n‐3 and n‐6 PUFA were observed for the same species. The results provide valuable information for preparing diet tables.     

Solubilities of solid n‐alkanes in methane: Data analysis and models assessment

This article reviews the results of experiments underway since 1950 studying the solid solubility of n‐alkanes (from ethane up to n‐triacontane) in methane and the factors influencing the global phase equilibrium behavior of the related binary mixtures. The methodology used consists of a series of comparisons of data in the composition‐temperature and pressure‐temperature diagrams. The kind of global phase diagram of the binary mixtures of methane referred to in the present article is found to be dependent of the ratio between the triple‐point temperature of the generic n‐alkane and the critical‐point temperature of methane. The Peng‐Robinson (1976), Predictive Soave‐Redlich‐Kwong, and Predictive Peng‐Robinson (1978) equations of state have been applied and compared with respect to the calculation of bivariant, univariant, and invariant equilibrium data involving solid n‐alkanes in binary mixture with methane. The fugacities of the solid n‐alkanes have been calculated by means of the so‐called classic approach. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2219–2239, 2018     

Gold(I)‐Catalyzed Decarboxylation of Propargyl Carbonates: Reactivity Reversal of the Gold Catalyst from π‐Lewis Acidity to σ‐Lewis Acidity

A cationic gold(I)‐catalyzed decarboxylative etherification of propargyl carbonates to selectively produce propargyl ethers is reported. In the reaction the gold(I) catalyst shows a distinct σ‐Lewis acidity rather than the commonly observed π‐Lewis acidity, and thus catalyzes the decarboxylation of a variety of propargyl carbonates to give the corresponding propargyl ethers with high selectivity. This reaction represents a rare example of the tunable reactivity of cationic gold(I) complexes between σ‐Lewis acidity and π‐Lewis acidity.

     

1H‐ and 13C‐NMR spectroscopic study of chemical equilibria in the system acetaldehyde + water

Acetaldehyde is an important intermediate in the chemical industry and often used in mixtures with water. These mixtures are reactive multicomponent systems, as acetaldehyde forms oligomers with water. Quantitative studies of the resulting speciation are scarce in the literature and limited to the formation of the smallest oligomer, ethane‐1,1‐diol. Therefore, in the present work, a comprehensive study of chemical equilibria in mixtures of acetaldehyde and water was carried out by quantitative ¹H‐ and ¹³C‐NMR spectroscopy. The study covers temperatures between 275 and 338 K and overall acetaldehyde mole fractions between about 0.05 and 0.95 mol/mol. The peak assignment is given for both the ¹H‐ and ¹³C‐NMR spectra. From the speciation data, obtained from the peak area fractions, numbers for the chemical equilibrium constants of the oligomer formation are obtained and a correlation is presented. © 2014 American Institute of Chemical Engineers AIChE J, 61: 177–187, 2015     

Preparation of Dimethyl Disulfide Adducts from the Mono‐Trans Octadecadienoic Acid Methyl Esters

The dimethyl disulfide (DMDS) adduct method is one of the more effective methods for determining double bond positions of dienoic acid. The DMDS method can be simply used to obtain the characteristic ions in which cleavage occurs between the methylthio group‐added double‐bond carbons as can be seen in the mass spectrum obtained using gas chromatography/electron ionization‐mass spectrometry. In the case of the methylene‐interrupted di‐cis type and di‐trans type dienoic acid, the DMDS addition reaction only occurs at one double‐bond position, and cannot occur at the remaining double‐bond position due to steric hindrance. As a result, two types of adducts are produced in the addition reaction. However, in the case of the methylene‐interrupted mono‐trans (mono‐cis) type dienoic acid, the DMDS addition reaction only occurs at the cis‐double bond. As a result, one type of adduct is produced in the addition reaction. In this report, we investigate the cause of the reaction selectivity by focusing on the addition reaction time.     

Hydromagnetic non‐Darcy flow,heat and mass transfer over a stretching sheet in the presence of thermal radiation and Ohmic dissipation

A numerical analysis has been carried out to study magnetohydrodynamic boundary layer flow, heat and mass transfer characteristics on steady two‐dimensional flow of an electrically conducting fluid over a stretching sheet embedded in a non‐Darcy porous medium in the presence of thermal radiation and viscous dissipation. The governing partial differential equations are convected into a system of nonlinear ordinary differential equations by similarity transformation and are solved numerically by using the Successive linearisation method, together with the Chebyshev pseudo‐spectral collocation method. The effects of various parameters on the velocity, temperature, and concentration fields as well as on the skin‐friction coefficient are presented graphically and in tabular forms.     

Titanium‐Mediated Direct Carbon‐Carbon Double Bond Formation to α‐Trifluoromethyl Acids: A New Contribution to the Knoevenagel Reaction and a High‐Yielding and Stereoselective Synthesis of α‐Trifluoromethylacrylic Acids

An efficient strategy for a high‐yielding and stereoselective synthesis of α‐trifluoromethyl unsaturated carboxylic acids directly from the reactions of 3,3,3‐trifluoropropanoic acid (CF₃CH₂COOH) with various aryl aldehydes in the presence of titanium tetrachloride (TiCl₄) is reported here for the first time, which is a valuable expansion for the classical Knoevenagel reaction. Because these compounds may have potential applications in organic electronics and can be easily converted to the corresponding fluorinated alcohols and amino acids with excellent bioactivity, this route should be a good choice for the preparation of α‐trifluoromethyl‐containing derivatives.     

Solvent‐ and Transition Metal Catalyst‐Dependent Regioselectivity in the [3+2] Cyclocondensation of Trifluoromethyl‐α,β‐ynones with Hydrazines: Switchable Access to 3‐ and 5‐Trifluoromethylpyrazoles

The regioselectivity of the [3+2] cyclocondensation of trifluoromethyl‐α,β‐ynones with hydrazines can be readily tuned to preferentially afford either 3‐ or 5‐trifluoromethylpyrazoles through variation of the reaction conditions. Under catalysis with copper(II) acetate (2.0 mol%), cyclocondensation proceeded smoothly to yield 3‐trifluoromethylpyrazoles with high regioselectivity. In contrast, when the reaction was conducted in dimethyl sulfoxide under catalyst‐free conditions, the formation of 5‐trifluoromethylpyrazoles was predominantly observed.

     

Enzyme‐assisted aqueous extraction of oil and protein from canola (Brassica napus L.) seeds

The emphasis of this study was to investigate the effect of enzymes on aqueous extraction of canola (Brassica napus L.) seed oil and protein. Four enzymes, Protex 7L, Multifect Pectinase FE, Multifect CX 13L, and Natuzyme, were tested for their effectiveness in releasing oil and protein during aqueous extraction. The enzyme‐extracted oil content of canola seeds (22.2–26.0%) was found to be significantly (p <0.05) higher than that of the control (without enzyme) (16.48%). An appreciable amount of protein (3.5–5.9%) originally present in the seed was extracted into the aqueous and creamy phases during aqueous extraction of oil. The physicochemical properties of oils extracted from canola seed by conventional solvent extraction, and aqueous extraction, with or without enzyme addition were compared. Significant (p <0.05) differences were observed in free fatty acid content, specific extinctions at 232 and 270 nm, peroxide value, color (1‐inch cell) and concentration of tocopherols (α, γ, and δ). However, no significant variation (p <0.05) was observed in iodine value, refractive index (40 °C), density (24 °C), saponification value, unsaponifiable matter and fatty acid composition. A better oil quality was obtained with aqueous extraction (with and without enzyme) than with solvent extraction. While the enzymes enhanced the oil extraction, the oil yield was still significantly (p <0.05) lower than that obtained by solvent (hexane) extraction.     

Efficient Lipase‐Catalyzed Kinetic Resolution and Dynamic Kinetic Resolution of β‐Hydroxy Nitriles. Correction of Absolute Configuration and Transformation to Chiral β‐Hydroxy Acids and γ‐Amino Alcohols

Chemoenzymatic dynamic kinetic resolution of β‐hydroxy nitriles 1 has been carried out using Candida antarctica lipase B and a ruthenium catalyst. The use of a hydrogen source to depress ketone formation in the dynamic kinetic resolution yields the corresponding acetates 2 in good yield and high enantioselectivity. It is shown that the ruthenium catalyst and the enzyme can be recycled when used in separate reactions. We also report on the preparation of various enantiomerically pure β‐hydroxy acid derivatives and γ‐amino alcohols from 1 and 2. The latter compounds were also used to establish the correct absolute configuration of 1 and 2.     

Occurrence of Hexacosapolyenoic Acids 26:7(n‐3), 26:6(n‐3), 26:6(n‐6) and 26:5(n‐3) in Deep‐Sea Brittle Stars from Near the Kuril Islands

Significant amounts of polyunsaturated fatty acids (PUFA) with a chain length of 26 carbon atoms were detected in lipids of five deep water species of Ophiuroidea besides common fatty acids with chain lengths between 14 and 24. By means of hydrogenation, GC–MS of the methyl esters, and 4,4‐dimethyloxazoline (DMOX) derivatives of these C26 acids were characterized as 5,8,11,14,17,20,23‐hexacosaheptaenoic [26:7(n‐3)]; 8,11,14,17,20,23‐hexacosahexaenoic [26:6(n‐3)]; 5,8,11,14,17,20‐ hexacosahexaenoic [26:6(n‐6)]; and 11,14,17,20,23‐hexacosapentaenoic [26:5(n‐3)]. Concentrations of these acids varied from 0.3 to 4.5 mol% of the total FA. In all the samples investigated, the main component of C26PUFA was hexacosaheptaenoic acid 26:7(n‐3). These C26PUFA are localized mainly in polar lipids. The presence of the possible biosynthesis precursors suggests that the C26PUFA are produced by the brittle stars, and are not accumulated from food sources. This finding can also explain the presence of small amounts of the 26:7(n‐3) acid detected earlier in flesh lipids of the roughscale sole Clidoderma asperrimum, which feeds on deep water brittle stars. We suggest a possible scheme of the biosynthesis of C26 PUFA.