The analysis of sterol degradation products to detect vegetable fats in chocolate

A method for the detection of hydrocarbon sterol degradation products (sterenes) has been adapted for the analysis of noncocoa butter vegetable fats in chocolate. The method involves solvent extraction of the fat separation of the sterene fraction, and analysis of individual sterenes with mass spectrometric detection. The sterene composition of refined noncocoa vegetable fats was determined in samples of cocoa butter, and retail chocolates. The presence of known sterenes was confirmed for all of the refined vegetable fats and for a single sample of cocoa butter, the processing history of which was not known. Detection of vegetable fat added to chocolate at the 5% level was demonstrated. Sterenes were detected only in chocolates labeled as containing vegetable fats. This technique has potential use as a screening method for the detection, but not quantification, of refined vegetable fat in chocolate.     

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.     

Detection of animal fats in butter by differential scanning calorimetry: A pilot study

Because of its high price, butter has always been the object of adulteration by addition of less expensive vegetable or animal fats. Although a number of methods have been proposed for the detection of butterfat adulteration, none has found widespread use. For this reason, a study was conduced to assess the use of differential scanning calorimetry (DSC) for detecting the presence of added animal fat, i.e., chicken fat, in butter. The results obtained show that DSC is an efficient method for characterizing pure animal fats as well as their mixtures. Furthermore, the accuracy with which data are obtained, in combination with the sensitivity of DSC to subtle changes in chemical composition of the sample, makes DSC an attractive possibility for development as a quality control procedure.     

Optical activity of lactones from animal and vegetable fats

The isolation of optically active lactones from animal and vegetable fats is described. As the optical activity of lactones isolated from butterfat is ascribed to their biological origin, special attention was paid to the optical purity of the lactones. Lactone mixtures from butterfat, goat milk fat and coconut oil were found to be dextrorotatory, those from babassu oil levorotatory. The total lactone mixtures of two out of three samples of palm-kernel oil were slightly dextro-, whereas that of the third one was levorotatory. After isolation of the individual lactones from the mixtures, levo- and dextrorotatory lactones were demonstrated side by side in palm-kernel oil and in coconut oil. The δ-lactones of palmkernel oil were levo-, the γ-isomers dextrorotatory. In coconut oil only the δ-C₁₂ lactone was levorotatory, whereas the other components of the δ-series were dextrorotatory. The specific rotation [a] _d of the chemically pure lactones was considerably lower than that of model lactones, this being an indication of their optical impurity. As it was evident from model experiments that no racemization of the lactones occurred during isolation, it follows that both optical antipodes are formed in the fats in unequal amounts, via different pathways.     

Simultaneous determination of ascorbyl palmitate and nine phenolic antioxidants in vegetable oils and edible fats by HPLC

This study describes an HPLC method for the simultaneous determination of ascorbyl palmitate (AP) and synthetic phenolic antioxidants (SPA) in vegetable oils and edible fats in a single run. To achieve this, citric acid was used in combination with isoascorbic acid for stabilization of AP in standard and sample solutions and for deactivation of oxidizing agents in the HPLC system. SPA and AP were directly extracted from samples with methanol containing 1 mg/mL each of citric acid and isoascorbic acid. HPLC analytical and guard columns were pretreated with 90% methanol/acetonitrile 1∶1 (vol/vol), containing 4 mg/mL each of citric acid and isoascorbic acid, and 10% water at pH 3, for 30 min. Under these conditions, AP was stable for about 7 h at room temperature. The relative SD of repeatability for AP (0.5–3.6%) was comparable to that for SPA (0.3–2.8%). Average recovery from spiked samples was 100% for AP, 98–103% for SPA, and 85% for BHT (up to 90% using double extraction with methanol).     

Enzymic hydrolysis of animal fats in organic solvents at temperatures below their melting points

Lipase fromCandida rugosa catalyzed the hydrolysis of inedible beef tallow and pork lard (edible and inedible) in the presence of organic solvents at temperatures below the melting point of the fat. Reactions were carried out at 50% substrate with 180 lipase units per gram of fat in a two-liter reactor. In the presence of isooctane (5-10%) beef tallow yielded 94% hydrolysis in 24 hr both at 37° and 31°C. Edible pork lard yielded 97% hydrolysis under these conditions and at temperatures as low as 25°C, while inedible lard gave hydrolysis intermediate between the other two fats.     

Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.     

Determination of the glyceride structure of fats; analysis of 14 animal and vegetable fats

The glyceride compositions of seven animals and seven vegetable fats have been determined by GLC analysis of the oxidized esterified glycerides as described in an earlier paper in this series. The compositions determined are compared with those calculated from lipase hydrolysis data according to the method of VanderWal. Good agreement was found between the calculated and determined compositions for the majority of the 14 fats. The exceptions were human fat and the more satu-rated vegetable fats, palm oil and cocoa butter, where some discrepancies occurred. Issued as NRC No. 8052. National Research Council of Canada Postdoctorate Fellow.     

A new analytical procedure to differentiate virgin or non‐refined from refined vegetable fats and oils

The effects of individual steps of industrial refining on the alteration of triacylglycerides (TAG) are reported. The level of dimer triglycerides, normally not present in crude oils, increased after each refining step, especially after steam‐washing and desodorisation. A good correlation between the applied temperatures and dimer triglycerides content was found. The forming of dimer triglycerides starts at 90 °C and increases corresponding to the extension of thermal treatment like normal heating or desodorisation. The data for various types of vegetable oils demonstrate that there is no clear‐cut different tendency to form dimers. Heated oils with different contents of linoleic acid produced nearly the same amount of dimers. Other criteria, like the determination of trans fatty acids, steradienes, or the UV‐absorption, were found not to be appropriate to detect a thermal treatment at temperatures below 150—170 °C. The formation of steradienes mainly depends on the total sterol contents, the percentage of added bleaching earth, and its acidity and moisture. Over 160 commercial vegetable oil samples were analysed to obtain a data range on the content of dimerised triglycerides. Mostly, vegetable oils Iabelled as non‐refined (which may be steam‐washed) did not exceed dimer contents of 0.1%. Virgin vegetable oils did not contain dimers (< 0.05%). The content of dimer triglycerides in vegetable oils was determined by a new method via clean‐up on a short silica gel column, followed by size‐exclusion HPLC with refractive index detection.     

First double bond site distributions in 16 vegetable and six animal reserve fats

The dibasic acids corresponding to the first double bond site in 16 vegetable and 6 animal fats were obtained by standardized procedures, fractionated by liquid-liquid countercurrent extraction and individual fractions analyzed. Results show that the site of the first double bond is not restricted exclusively or even predominantly to any single position but is spread over three or more positions in major proportions. First double bond site distributions show large differences in different biological species, different varieties from the same species and also different specimens from the same variety. Possible migration of double bonds in permanganate oxidation at alkaline pH is discussed.     

Easy mass spectrometry for metabolomics and quality control of vegetable and animal fats

Easy ambient sonic spray ionization (EASI), a novel desorption/ionization technique for ambient mass spectrometry analysis, is shown to permit the characterization of different types of vegetable and animal fats. The taxonomic markers of the oils, mainly fatty acids and phenols, are extracted with methanol/water (1:1) solution and made alkaline with NH₄OH, then placed and dried on the surface of a glass tip and directly analyzed by EASI‐MS in the negative‐ion mode. EASI provides a supersonic cloud of charged droplets that causes efficient desorption and ionization of the oil markers directly from the surface of the glass tip. As proof‐of‐principle cases, EASI(?)‐MS was applied to genuine samples of olive oil, hazelnut oil, soybean oil, grape seed oil, canola oil, butter, and lard. Characteristic metabolomics EASI(?)‐MS profiles of fatty acids and eventually phenols were obtained.     

Analysis of free and esterified sterols in vegetable oils

In vegetable oils, phytosterols occur as free sterols or as steryl esters. Few analytical methods report the quantification of esterified and free sterols in vegetable oils. In this study, esterified and free sterols were separated by silica gel column chromatography upon elution with n-hexane/ethyl acetate (90∶10 vol/vol) followed by n-hexane/diethyl ether/ethanol (25∶25∶50 by vol). Both fractions were saponified separately and the phytosterol content was quantified by GC. The analytical method for the analysis of esterified and free sterols had a relative standard deviation of 1.16% and an accuracy of 93.6–94.1%, which was comparable to the reference method for the total sterol analysis. A large variation in the content and distribution of the sterol fraction between different vegetable oils can be observed. Corn and rapeseed oils were very rich in phytosterols, which mainly occurred as steryl esters (56–60%), whereas the majority of the other vegetable oils (soybean, sunflower, palm oil, etc.) contained a much lower esterified sterol content (25–40%). No difference in the relative proportion of the individual sterols among crude and refined vegetable oils was observed.     

油脂加氢催化剂研究现状及发展趋势

本文介绍了油脂加氢催化剂的研究现状，指出氢化催化剂的发展趋势是由单元体金属向多元体金属、由贵金属向贱金属、由多相催化剂向均相催化剂过渡。     

Computational estimation of the triacylglycerol composition of vegetable fats from gas and liquid chromatography data

A mathematical framework was described and discussed that relates the triacylglycerol (TAG) distribution to measurements results. This model is valid for any analytical technique for which an unambiguous relation between the TAGs and the experimental data exists. The framework can be employed to estimate the TAG distribution based on any subset of these analytical techniques. Furthermore future techniques can be incorporated, eventually enabling the computation of the exact TAG distribution. In current practice the relation from measurement values to the TAG distribution is believed to be described by Coleman's theory. However some natural fats and fractions of fats are known to be non‐adherent to Coleman's theory. For both palm stearin and palm kernel oil this notion is tested and confirmed. For these fats a different approach is needed to be able to estimate the TAG distribution. Within the framework three different approaches for making an estimation of the TAG distribution based on measured data are described, discussed and compared with Coleman's results: a least squares approach, a genetic algorithm (GA) approach and an expectation maximisation (EM) approach. The results presented demonstrate that the estimated TAG distributions from the GA and EM algorithm are significantly better than Coleman's estimate and the least squares approach. Overall the EM algorithm is favoured because of its consistency.     

Composition and thermal properties of cattle fats

The physical‐chemical properties, fatty acid composition and thermal properties of cattle subcutaneous, tallow and intestinal fats were determined. Subcutaneous fat differed from the other fat types with respect to its lower melting point (29.0 °C) and higher saponification (211.4 mg KOH/g) and iodine (50.55) values. The cattle fat types contained palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n‐9) and linoleic acid (18:2n‐6) as the major components of fatty acid composition (24.58–25.90%, 10.21–33.33%, 28.18–46.05%, 1.54–1.73%, respectively). A differential scanning calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major peaks (T_peak) of tallow and intestinal fats were similar and determined as 24.10–27.71 °C and 2.16–4.75 °C, respectively, for crystallization peaks and 7.09–9.39 °C and 43.28–46.49 °C, respectively, for melting peaks in DSC curves; however, those of subcutaneous fat (12.48 °C and –6.79 °C for crystallization peaks and 3.56 °C and 23.55 °C for melting peaks) differed remarkably from those of the other fat types.     

国内油脂加氢催化剂现状及发展趋势

叙述了国内油脂加氢催化剂的研究现状,包括催化剂的制备方法和在油脂加氢方面的应用,指出油脂氢化催化剂的发展趋势是向超细及非晶态催化剂发展。     

Vegetable oils and animal fats as alternative fuels for diesel engines with dual fuel operation

Vegetable oils and animal fats are applicable as fuels in standard diesel engines after having adapted the fuel system for electronically controlled dual fuel regime oil/fat-fossil diesel. In this contribution, performance and emission characteristics of the engines running on rapeseed oil, lard, or chicken fat are given and compared to those of fossil diesel and fatty acid methyl esters. The results of engine tests of these fuels show a decrease in maximum power and maximum torque in comparison to fossil diesel due to a lower energy content of triacylglycerols. These values are influenced also by a type of the engine used at testing. When compared to fossil diesel, the opacity of oil/fat based fuels is higher for an engine with lower injection pressures while it is lower for an engine with higher injection pressures. The level of both controlled and uncontrolled emissions is low for all tested biofuels and is low also for the reference fossil diesel. The results of performance and emission tests for rapeseed oil containing 3 and 6 vol.% of anhydrous ethanol are comparable to those obtained for pure oil. In this paper, practical experiences based on long-term operation of adapted vehicle fleet fuelled with oil/fat-fossil diesel are mentioned.     

油脂市场回顾及未来走势

回顾了2009年的油脂市场,同时,对2010年的国内外油脂市场的油脂作物的产量、油脂产品的消费和库存等方面进行了分析。指出了2010年度影响油脂市场的因素。最后,展望了未来油脂市场的发展趋势。