Transesterification and On-Line LC-GC for Determining the Sum of Free and Esterified Sterols in Edible Oils and Fats

A method is proposed to substitute the classical saponification procedure for the determination of the sterols and other minor components in edible oils and fats. Saponification is replaced by transesterification, which liberates sterols and alcohols from esters under mild conditions, but does not form soap hindering the extraction of the neutrals. Triglycerides are turned into fatty acid methyl esters, which are removed by automated LC-GC. LC also pre-separates the minor components into classes, e.g., of linear alcohols, triterpenes, methyl sterols, Δ5 sterols, and Δ7 sterols. Multiple LC-GC transfer allows obtaining several gas chromatograms from the same injection into LC. Sample preparation takes some 5 min; 10-25 samples can be analyzed by an LC-GC instrument, depending on the number of LC fractions transferred to GC per sample.     

Recognition of Adulterated Oils by Direct Analysis of the Minor Components

Recognition of adulteration by other oils via direct analysis of the minor components (“sterol fraction”) is shown for olive oil. 10 % of various oils were admixed, the free alcohols silylated and the minor components analyzed by on-line coupled LC-GC-FID. For most oils, even smaller additions can be recognized. Admixed oils can no longer be determined, however, if their minor components have been removed by strong raffination. Bleaching of rapeseed oil with 7% of earth at 180 °C, in fact, completely removed free and esterified sterols.     

Determination of Raffination of Edible Oils and Fats by Olefinic Degradation Products of Sterols and Squalene,Using Coupled LC-GC

Raffination of edible oils and fats, i.e. bleaching with earth or charcoal as well as deodoration, can be determined by the analysis of dehydroxylation products of sterols and isomerization products of squalene. These olefinic degradation products are isolated from the rest of the oil by LC on silica gel and on-line transfer to GC. Sample preparation consists of preparing a 20% solution of the oil. Nearly half of the “extra virgin” olive oils analyzed contained such products, but concentrations were too low for assuming admixture of regularly refined oils. However, many other oils advertized as non-refined turned out to have been treated beyond declaration.     

Quantitative Determination of Erucic Acid in Edible Oils and Fats Containing Marine Oils and/or Hydrogenated Fats

A method has been developed for the quantitative measurement of erucic acid in complex samples of oils or fats containing marine oils and/or hydrogenated fats. A two step procedure is proposed: in a first step the constituent fatty acids of the transesterified oil or fat are resolved on a silver-nitrate-impregnated silicagel thin-layer in function of the degree of unsaturation and the double bond localization. Positional isomers migrating slowlier on the thin-layer than erucic acid (e. g. cetoleic acid often present in large amounts in marine oils) are distinctly separated in this way. In a second step components moving ahead of the cetoleic acid (e. g. erucic acid, the added internal standard and geometrical isomers of erucic acid) are scraped off from the thin-layer plate and the erucic acid is determined by gas chromatography on a packed column with a liquid crystal, operated in the nematic phase temperature region, as the stationary phase. In complex samples recoveries of 90 to 102% are reported with overall relative standard deviations of 2.5 to 3%.     

Studies in Interesterification — Part I Production of Edible Fats from Vegetable Oils by Directed Interesterification

A modification of the Eckey's directed interesterification process of individual fats and their mixtures has been studied. The fat after directed interesterification with NaOMe catalyst (0.4% w/w) was first chilled at 15° C for variable lengths of time (30 mts. — 180 mts.) and then subjected to further reaction at ca. 23° C from 12 hrs. — 168 hrs. depending on the type of fat and products desired to produce fats of different melting ranges. It was established that the above pretreatments influenced the end products but a minimum content of ca. 20% saturated fatty acids over C₁₆ was necessary to produce a fat of melting range 36°–38° C.     

Capillary Supercritical Fluid Chromatography for the Analysis of Oils and Fats

The potential of Supercritical Fluid Chromatography (SFC) for the qualitative and quantitative analysis of triglycerides in oils and fats is evaluated. Results are compared with those obtained with High Temperature Capillary GC (HTCGC). SFC shows a distinct advantage over HTCGC with respect to the response factors of triglycerides. These appear to be mutually equal and drop only to 0.8 with respect to saturated triglycerides, when 9 double bonds are present. Precise quantification by SFC requires the use of internal standards, as the precision of absolute peak areas is much too low. With a view to qualitative identification of triglycerides, SFC offers less selectivity than HTCGC, more critical pairs being present.     

The Biotechnology of Fats – a Challenge and an Opportunity

Oleochemical products and biotechnological methods are making equally important contributions to a chemistry of the future which - energy-saving and kind to the environment - has its foundations in regenerative raw materials. In the past, research results of biochemistry have only indirectly affected oleochemistry - for example through crop improvements in oil plants. Although biotechnological processes for the modification or production of fats (for example by fermentation) have been investigated, they have only been adopted in a few specialized fields. However, with the general advance of the bioreactor and genetic engineering, many new and interesting ideas for the biotechnology of fats have been developed in recent years, including for example the commercial application of lipases for splitting fats and the use of bioemulsifiers for secondary and tertiary oil recovery. Further innovations are likely and are being discussed.     

天然油脂一步法烷氧基化及其产物乳化性能研究

以几种天然油脂(豆油、菜油、棕榈油、橄榄油)为原料,在自制FY系列催化剂作用下与环氧乙烷(EO)或环氧丙烷(PO)在140℃、0 3～0 4MPa下,经一步法嵌入反应得到乙氧基化油脂(EFO)或丙氧基化油脂(PFO)。测定了EFO和PFO的自乳化性能和乳化性能,并实验了大豆色拉油衍生EFO代替大豆色拉油作为原料复配润滑油剂及该油剂形成微乳状液的能力。实验结果表明,在油脂分子结构中嵌入EO或PO后,产物EFO及PFO的自乳化性能及乳化性能均得到提高。在该实验范围内,EFO的自乳化力最高可达原油脂的36倍,乳化力则提升140倍以上。含大豆色拉油衍生EFO的油剂与含大豆色拉油的油剂相比,油剂含油率高;在与水互溶时,前者具有更宽的微乳区域,且微乳液稳定性好;其中优选出的油剂配方可与水以任意比例混合均形成微乳状液。     

Thermodynamic Modeling of Multi‐phase Solid–Liquid Equilibria in Industrial‐Grade Oils and Fats

Compositional thermodynamic phase separation is investigated for industrial‐grade vegetable oils with complex compositions. Solid–liquid equilibria have been calculated by utilizing the Margules 2‐suffix activity‐coefficient model in combination with minimization of the Gibb's free energy of the system. On the basis of quasi‐equilibrium solid‐fat content (SFC) measurements, a new approach to the estimation of the interaction parameters, needed for the activity‐coefficient model, has been developed. The parameters are fitted by matching the SFC of two oils at various degrees of dilution and isothermal temperatures. Subsequently, the parameters are successfully validated against three oils, rich in asymmetric and symmetric triacylglycerols (TAG), respectively. The new approach developed is shown to be very flexible, allowing incorporation of additional TAG and polymorphic states. It thereby provides a simple way to dealing with multi‐component, multi‐phase TAG mixtures without having the required binary interaction parameters at hand a priori. This ultimately provides a powerful, predictive tool which may serve as a starting point for laboratory screening and creation of tailor‐made products because many different oil mixtures can be evaluated quickly with respect to specific properties, prior to more time‐consuming experimental evaluation.     

Comprehensive Triacylglycerol Characterization of Oils and Butters of 15 Amazonian Oleaginous Species by ESI‐HRMS/MS and Comparison with Common Edible Oils and Fats

The Amazon rain forest encompasses an extraordinary source of vegetable oils with many applications, especially for food, pharmaceutical and cosmetics industries. In this work, the main composition of fifteen Amazonian oils and butters are investigated via gas chromatography‐mass spectrometry (GC‐MS) and electrospray ionization high resolution mass spectrometry (ESI‐HRMS). Triacylglycerols (TAG) are characterized by their fragmentation spectra and comparison with the LIPID MAPS database, resulting in a detailed compendium of TAG composition of these samples. Over 70 different TAG are putatively annotated per sample and the occurrence of isomers is remarkable, showing that TAG complexity in these samples is considerably higher than ever reported. The TAG composition of the Amazonian samples are also statistically evaluated using principal component analysis (PCA) for comparison to common edible oils such as soybean, corn, coconut, and olive oil. Some tendencies of grouping are observed: butters with medium chain fatty acids (FA); butters with high oleic FA; and oils with high oleic and high linoleic FA contents. This study provided profiles that ensure Amazonian oils and butters authenticity, quality and also aids in understanding their properties and the best applications for each. Practical Applications: It is expected that this comprehensive set of data on the TAG composition of Amazonian oils and butters will help guide the use and applications of these products, providing consumers with the best benefits from a nutritional perspective. Moreover, adulterations could be more easily detected when a database is available, since the chemical composition of certified samples is investigated in this work. Ultimately, this study can encourage the sustainable production and applications of Amazonian oils and appropriate use of Amazon rain forest resources.     

Structural Modifications of 4,4′-Dimethyl Sterols during the Hydrogenation of Edible Vegetable Oils

The structural changes induced by the hydrogenation of dietary vegetable oils affect not only fatty acids but sterolic components too, especially C-24-methylene and C-24-ethylidene sterols. The main alterations found in the triterpene alcohols involve 24-methylene-cycloartenol and, to a lesser extent, cycloartenol. Of the three potential hydrogenation-induced reactions to affect these compounds, i. e. hydrogenation of the double ethylene bonds, the opening of the cyclopropane ring and the isomerization of the double bonds in the side chain, the latter is predominant. Cyclobranol and cyclosadol from 24-methylene cycloartanol and 9β,19-cyclo-5α-lanost-25-en-3β-ol from cycloartenol account for most of the structural isomers formed.     

A Greener Alternative Titration Method for Measuring Acid Values of Fats,Oils, and Grease

A greener alternative method is proposed for measuring acid values (AV) of fats, oils, and grease (FOG) based on visual titration. Compared with Official Method Cd 3d-63 of the American Oil Chemists' Society (AOCS), this greener alternative method can eliminate the use of toluene, which in turn reduces toxicity and cost. A total of 44 samples of yellow and brown grease with AV ranging from 0.13 to 170.37 (mg KOH) g⁻¹ were titrated using both methods. The alternative titration method can provide accurate and reliable results to determine the AV of FOG by various statistical analyses including repeatability, linear regression, f-test, t-test, and method accuracy calibration with AOCS Cd 3d-63. This low-cost method can be recommended for routine titration in research and development, and in biodiesel plants for most FOG samples.     

A Visual Titration Method for the Determination of the Acid Number of Oils and Fats: a Green Alternative

A visual and green titrimetric method is proposed for the determination of the acid number of oils and fats. The sample is dissolved in a water–ethanol mixture (1:1 v/v) and titrated with a 0.02?mol L^?1 aqueous NaOH solution. Phenolphthalein is used as acid-basic indicator. Oils of canola, sunflower, linseed, castor, corn and soy as well as swine lard, a total of twelve real samples, were analyzed. The results obtained were compared with those from the application of the AOCS Cd 3d-63 method, through a statistical linear regression procedure at the 95?% confidence level and no evidence for systematic differences between the two sets of results was observed. The mean RSD (relative standard deviation ) for the proposed procedure is 4.8?%, whereas that of the official method was found to be 5.4?%.