A rapid method for the determination oftrans unsaturation in fats and derivatives

Thetrans unsaturation present in samples of unsaturated fats and derivatives may be determined from measurement of the infrared absorbance at two wavelengths, one due totrans configuration of a double bond and the other due to the ester or acid group. The ratio of the two absorbance values has a linear relationship with thetrans unsaturation content. Thus, a drop of sample is diluted with CS₂ and the infrared absorbance measured at 10.36 μ and at 8.5–8.6 μ if esters and 10.7 μ if acids. To calculate the per cent isolatedtrans double bonds in the sample, the ratio of the two absorbance values is substituted into the linear equation which was developed from known samples. The method is rapid since the sample need not be weighed nor made up to a known volume and thus may be applied to samples such as those collected from a gas chromatograph or after thin layer chromatography. Presented at the AOCS Meeting, New York, October 1968.     

A rapid method for the estimation of unsaturation of fats and oils by use of hypochlorous acid reagent

Summary A rapid method for the determination of unsaturation of oils and fats containing non-conjugated ethylenic linkages has been developed, using hypochlorous acid as the reagent. The method has several advantages,viz., that the estimation is conducted with an aqueous solution of sodium hypochlorite reagent, and moreover no oil solvent is required for the estimation. In all the methods currently employed, the reagents used must be perfectly anhydrous otherwise incomplete addition will take place, giving low results. Since a reaction time of 4 to 5 min. is recommended, the estimations are much more rapid than the customary Wijs or Hanus methods. No discrimination as to time factor need be made for oils possessing different degree of saturation. All oils, whether belonging to non-drying or drying groups, give accurate results within the specified time. There is no secondary reaction except in the case of castor oil, but even in that case the secondary reactions are not appreciable within the first hour of reaction. The present method compares favorably with the standard procedures currently employed for determination of unsaturation.     

A rapid method for the analysis of hydrogenated fats by GC with IR detection

A rapid method for analysis of trans and cis FA in hydrogenated fats has been developed. The method is based on a single anlaysis by CG with IR detection. Multivariate partial least squares regression is applied on the IR spectra to predict the number of cis and trans double bonds. For each chain length the method provides information about the amount of the saturated FA, the amount of trans monoenes, the amount of cis monoenes, the amount of PUFA, and the average number of cis and trans double bonds in PUFA. The method has been validated by summing the values to a total trans value and total unsaturation. These sum values were compared with total trans unsaturation, as determined by AOCS method Cd 14-95, and iodine value, as determined by AOCS Cd 1d-92.     

Fate of dietary sterols in hydrogenated oils and fats

Samples of table margarines, so-called polyunsaturated table margarines, hydrogenated vegetable oils, and so-called polyunsaturated hydrogenated vegetable oils were shown by infrared spectroscopy to contain hydrogenated components. Examination of the sterols from these oils by argentation thin layer chromatography and gas liquid chromatography did not reveal campestanol, stigmastanol, or Δ²²-stigmastenol, the expected hydrogenation products of the natural sterols. The sterol compositions of the above samples, animal fats, and blends of hydrogenated vegetable oils and animal fats were determined. The compound 24-methyl cholest-7-en-3β-ol was identified tentatively in sunflower and safflower oils.     

Simplified method for the determination oftrans monoenes in edible fats by TLC-GLC

Several modifications of an established thin-layer chromatography-gas-liquid chromatography (TLC-GLC) procedure for quantitatingtrans unsaturated fatty acids in edible fats are presented. These refinements considerably simplify the procedure without affecting accuracy. The modifications include: i) the use of pre-coated silica sheets, dynamically impregnated with Ag⁺, which allow separated bands to be cut off with a pair of scissors; and ii) the use of stearic acid in the deliberately combined saturated andtrans monounsaturated fatty acid methyl ester bands as an (endogenous) internal standard.Trans values thereby obtained agree favorably with the results from the conventional technique.     

Determination of ultratrace metals in hydrogenated vegetable oils and fats

Ultratrace levels of nickel, chromium, copper and iron occurring in hydrogenated vegetable oil products were estimated by dispersion of the samples in 4 methyl-2-pentanone and atomic absorption analysis by the graphite furnace technique. The principal goals in establishing the analytical methods were improved sensitivity to metals at low levels and applicability to limited amounts of products. Using reproducibility and linearity of response as criteria, optimum oil concentration in solvent and instrument parameters were established. For a series of commercial products, the method of standard addi-tions was adopted to correct for matrix differences between the products and salad oil-based standards. The range for the metals was determined in five cooking oils: Ni, 29–207 ppb; Cr, 1–5 ppb; Cu, 13–37 ppb; and Fe, 138–301 ppb; in recovered oils from five margarines: Ni, 34–70 ppb; Cr, 2–12 ppb; Cu, 26–58 ppb; and Fe, 239–540 ppb; and in five solid shortenings: Ni, 592–2772 ppb; Cr, 8–35 ppb; Cu, 26–108 ppb.     

Tetramethylguanidine catalyzed transesterification of fats and oils: A new method for rapid determination of their composition

A new method for the rapid preparation of methyl esters from vegetable oils and fats, using tetramethylguanidine as catalyst, has been developed. This method is compared with the traditional method (Ce 2–66, using 20% BF₃ in methanol) and that proposed by Hartman and Lago (using NH₄Cl/H₂SO₄ in methanol). It is shown that the new method produces the methyl esters in quantitative yields and has certain advantages, as it is simpler, cheaper and does not result in isomerization of the fatty acids.     

Direct determination oftrans unsaturation in triglycerides by infrared spectrophotometry

A differential infrared spectrophotometric method is described for the determination oftrans unsaturation in fats. The method utilizes absorption at 965 cm⁻¹, due to the C−H out-of-plane deformation vibrations oftrans unsaturated compounds. The method is rapid, accurate, and directly applicable to the determination oftrans unsaturation in triglycerides. It is applicable to samples which contain low concentrations oftrans acids (down to 2%) and also to samples with fatty acids of mixed chain length.     

A method to determine the monoglyceride content in fats and oils

A methodology was worked out to analyze monoglycerides present in fats and oils in low levels (<0.5%). The monoglycerides are enriched by acetonitrile extraction and further evaluated either by gas liquid chromatography or by a combination of thin layer chromatography-gas liquid chromatography. Results are presented showing the selectivity, yield, and reproducibility of the isolation step and the efficiency of the thin layer chromatography fractionation. Examples also are given demonstrating some possible applications of the proposed method.     

A rapid,automated method for the determination ofcis andtrans content of fats and oils by fourier transform infrared spectroscopy

A rapid Fourier transform infrared (FTIR) method was developed to simultaneously determine percentcis andtrans content of edible fats and oils. A generalized, industrial sample-handling platform/accessory was designed for handling both fats and oils and was incorporated into an FTIR spectrometer. The system was calibrated to predict thecis andtrans content of edible oils by using pure triglycerides as standards and partial least squares as the chemometric approach. The efficacy of the calibration was assessed by triglyceride standard addition, by mixing of oils with varyingcis/trans contents, and by analyzing fats and oils of known iodine value. Each of the approaches verified that the FTIR method measured thecis andtrans content in a reproducible (±0.7%) manner, with the measured accuracies being 1.5% for standard addition and 2.5% for the chemically analyzed samples. Comparisons also were made to the conventional American Oil Chemists’ Society (AOCS) method for the determination oftrans isomers by IR spectroscopy. The FTIR-partial least squares approach worked well over a wide range oftrans contents, including those between 0 and 15%. The sample-handling accessory designed for this application is robust, flexible, and easy to use, being particularly suited for quality-control applications. In addition, the analysis was automated by programming the spectrometer in Visual Basic (Windows), to provide a simple, prompt-based user interface and to allow an operator to carry outcis/trans analyses without any knowledge of FTIR spectroscopy. A typical analysis requires less than two minutes per sample. The derived calibration is transferable between instruments, eliminating the need for recalibration. The integrated analytical system provides a sound basis for the implementation of FTIR methods in place of a variety of AOCS wet chemical methods when analytical speed, cost, and environmental concerns are issues.     

A new and rapid method for the electron microscopic examination of fats

A replica technique was developed to study the crystal structure of fats using the electron microscope. The fats were frozen prior to replicating, and it was shown that differing rates of freezing produce structural differences within the fat. The use of Teepol solutions permitted a degree of separation of the solid and liquid phases, and the differences between crystals of the solid phase were shown.     

A simple method for the improvement of the keeping quality of oils and fats

Summary The efficiency of antioxidants is judged by means of a modified Swift test. Addition of 0.05% sulfur during the deodorizing process yields a 4-1.4 time prolonged keeping time of oils and fats. There is a linear relation between iodine value and the remaining speed of oxidation in % in the tests made with sulfur. The reduction of the velocity is inversely proportional to the iodine value. The effects of gallate and the sulfur seem to be additive. The residual amount of sulfur left in the oils and fats after deodorization is very small and only slightly higher than that present in ordinary deodorized oils and fats.     

Detection of interesterified fats in hydrogenated fats

Interesterification of fats is being used increasingly as an alternative to hydrogenation in preparing shortening and margarine bases. The detection of interesterified fats in vanaspati (a hydrogenated fat) is relevant because of possible adulteration problems. Either palmitic acid-rich or stearic acid-rich interesterified fats were blended with 13 market samples of hydrogenated fat (vanaspati) and examined by on-plate lipase hydrolysis of glycerides, gas chromatographic determination of fatty acids of the isolated 2-monoglycerides and calculation of two emperical indices. These were R₁, the ratio of the amounts of palmitic acid present in the 2-position to that in the total glyceride, and R₂, the ratio of saturated acid present in the 2-position to total saturated fatty acid in the fat. The vanaspati, R₁ was always below 10 and R₂ was always below 20. The presence of 5–10% interesterified fat raised both figures and offered a suitable basis for the detection of interesterified fats in hydrogenated fats.     

A rapid estimation of pigment content in virgin olive oils by a solvent-free method

In this work, a fast method was proposed for estimating the virgin olive oils (VOOs) carotenoids and chlorophylls concentration using color measurement. The pigment content by conventional spectrophotometry method and CIELAB color (L*, a*, and b*) at different degree of sample thickness (from 5 to 50 mm) of one hundred VOOs were measured. Oil carotenoids and chlorophylls content were correlated with the color parameters for the different oil thickness studied to design the prediction models of the new method. The best regression coefficients (R²) were obtained for multiple linear regression model using the three independent variables (L*, a*, and b*) together measured at 5 mm of oil thickness. The R² were 0.9679, 0.9515, and 0.9644 for predicting carotenoids, chlorophylls, and total pigments, respectively. External validation of these prediction models was satisfactory (relative error < 0.1). Therefore, this new solvent-free colorimetric method is a useful method for determination of carotenoids and chlorophylls content in VOOs. Practical applications: The simple colorimetric method developed in this study offers a fast and accurate alternative to current methods published in the literature to estimate the pigment content in VOOs. It is a rapid (less than 1 min) and cheap method, with the advantage of ease of operation, no sample pretreatment and solvent-free, thus environmentally friendly. This methodology can potentially be used by trained “nonprofessional analytical skilled” people in small laboratories or olive oil mills with limited technical facilities. Therefore, the technique is highly plausible as an alternative to determine the pigment content in VOOs. Finally, future works with this methodology could be carried out to online control of VOOs pigments content in the oil extraction process.     

Detection and estimation of dipalmito and distearo glycerides in hydrogenated oils

Journal of the American Oil Chemists' Society -     

A rapid instrumental method for the evaluation of the stability of fats

A rapid instrumental method for evaluation of stability of fats has been proposed. Acceleration of oxidation is accomplished by vigorous mixing of a heated sample with oxygen at atmospheric pressure. The volume of absorbed oxygen determined directly by means of a special manostatic device constitutes the measure of the course of the reaction. Experimental results are recorded on a strip-chart plot of the volume of oxygen absorbed as a function of time. The start of rapid absorption of oxygen at the end of the induction period is taken as the end point. Samples of commercial low-erucic rapeseed oil, soybean oil and lightly hydrogenated soybean oil had end points in the range of 50 to 100 at a temperature of 120 C.     

A coulometric method for the determination of low peroxide values of fats and oils

The AOCS official method for the determination of peroxide values of fats and oils has been modified to perform more precise analyses, especially in the range of extremely low values (peroxide value <1). In the newly developed method presented here, the final titrimetric step of an iodometric method has been replaced by an electrochemical technique, based upon coulometric reduction of the iodine at an electrode maintained at a controlled potential. Using this method peroxide values down to 0.06 were determined with reasonable precision. Finally, the influence of different parameters on the peroxide value obtained was investigated.     

A rapid oxygen bomb method for evaluating the stability of fats and shortenings

A modification of the A.S.T.M. oxygen bomb method for evaluating the stability of any fat within a period of six hours or less has been developed. It is based upon the addition of selected levels of a copper, catalyst, operating under the conditions previously used without catalyst. The precision of this bomb method has been characterized and the contributions of several factors to the overall variation have been estimated. The research indicates that it will not be possible to express bomb data in terms of AOM values by employing a factor. On the basis of precision obtained by this procedure, it is concluded that it should be readily adaptable to industrial control applications.