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1.
Pan-frying is a popular frying method at home and in many restaurants. Pan-frying stabilities of two frying oils with similar iodine values (IV)—mid-oleic sunflower oil (NuSun oil; IV=103.9) and a commercial canola oil (IV=103.4)—were compared. Each oil sample was heated as a thin film on a Teflon-coated frying pan at ∼180°C to a target end point of ≥20% polymer. High-performance size-exclusion chromatography analysis of the mid-oleic sunflower and canola oil samples indicated that the heated samples contained 20% polymer after approximately 18 and 22 min of heating, respectively. The food oil sensor values increased from zero to 19.9 for the canola sample and from zero to 19.8 for the mid-oleic sunflower sample after 24 min of heating. The apparent first-order degradation rate for the mid-oleic sunflower sample was 0.102±0.008 min−1, whereas the rate for the canola sample was 0.092±0.010 min−1. The acid value increased from approximately zero prior to heating to 1.3 for the canola sample and from zero to 1.0 for the mid-oleic sunflower sample after 24 min of heating. In addition, sensory and volatile analyses of the fried hash browns obtained from both oils indicated there were no significant differences between the two fried potato samples.  相似文献   

2.
A rapid direct Fourier transform infrared (FTIR) spectroscopic method using a 100 μ BaF2 transmission cell was developed for the determination of free fatty acid (FFA) in crude palm oil (CPO) and refined-bleached-deodorized (RBD) palm olein, covering an analytical range of 3.0–6.5% and 0.07–0.6% FFA, respectively. The samples were prepared by hydrolyzing oil with enzyme in an incubator. The optimal calibration models were constructed based on partial least squares (PLS) analysis using the FTIR carboxyl region (C=O) from 1722 to 1690 cm−1. The resulting PLS calibrations were linear over the range tested. The standard errors of calibration (SEC) obtained were 0.08% FFA for CPO with correlation coefficient (R 2) of 0.992 and 0.01% FFA for RBD palm olein with R 2 of 0.994. The standard errors of performance (SEP) were 0.04% FFA for CPO with R 2 of 0.998 and 0.006% FFA for RBD palm olein with R 2 of 0.998, respectively. In terms of reproducibility (r) and accuracy (a), both FTIR and chemical methods showed comparable results. Because of its simpler and more rapid analysis, which is less than 2 min per sample, as well as the minimum use of solvents and labor, FTIR has an advantage over the wet chemical method.  相似文献   

3.
Cloudiness in canola (Brassica napus) oil is currently tested using methods that involve cooling the oil samples and observing them for the development of cloudiness. Alternative methods include the use of solvents to increase sensitivity or speed. We compared traditional temperature-only cold tests and solvent cold tests for canola oils which sediment at room temperature, only while refrigerated, or not at all. All oils tested passed the American Oil Chemists’ Society cold test, and all but one heavily sedimenting oil passed a commercial refiner’s cold test. The efficiency of the commercial refiner’s test was improved by lowering the temperature from 15 to 7°C. Of the four solvents tested, acetone was the most effective in detecting cloudy oils. The most effective combination was a cold test using 70% cold acetone, observed after 6 h storage in an ice-water bath.  相似文献   

4.
Al-substituted mesoporous FSM-16 materials with different SiO2/Al2O3 (28–452) ratios have been synthesized by intercalating kanemite using cetyltrimethylammonium bromide (CTMABr) as the intercalating agent and sodium aluminate as the aluminium source, and characterized by different physico-chemical characterization techniques. The XRD measurements revealed a slightly disordered hexagonal packing of channels in the Al-FSM-16 samples. The thermal stability of Al-FSM-16 samples was confirmed by DTA analysis, where no structural changes were observed in the temperature range of 600–900°C. No significant changes were observed in the morphology of kanemite and the Al-FSM-16 sample obtained from kanemite as revealed by the SEM analysis. This result clearly indicated that the Al-FSM-16 sample is formed via a folded sheet mechanism. Moreover, TEM measurements confirmed the presence of a slightly disordered hexagonal array of channels in Al-FSM-16 in agreement with the XRD results. The BET surface areas (638–788 m2 g−1) and pore volumes (0.57–0.87 cm3 g−1) were indicative of the high porosity of the Al-FSM-16 samples. The Al-FSM-16 (SiO2/Al2O3 = 49) sample exhibited excellent hydrothermal stability at 150°C. The Al-FSM-16 samples were found to catalyze the isomerization of m-xylene to p- and o-xylenes.  相似文献   

5.
An adaptation of the American Oil Chemists' Society Official Method Cd 8–53 for determining peroxides in fats and oils using a 0.5-g sample is described. Comparisons of the Official Method and the small-scale method were performed by analyzing soybean oil samples spiked with t-butyl hydroperoxide and autoxidized soybean oil samples. A linear relationship between the Official Method and the small-scale method was obtained with an R 2 of 0.998. The small-scale method is sensitive, precise, and suitable for small sample sizes and uses only about 10% of the chemicals necessary for the Official Method.  相似文献   

6.
The thermal oxidation of four commercially available neat blown soybean oil samples and a heat-bodied soybean oil sample, obtained from various manufacturers, having Gardner bubble viscosities between Z2 and Z3 was investigated using nonisothermal DSC under a constant oxygen flow and a heating rate (β) ranging from 3 to 20°C/min. The extrapolated onset temperatures (T e1 and T e2 ) and maximum temperature of heat flow (T p2 ) at different β were determined from the DSC curves and used in conjunction with the Ozawa-Flynn-Wall method to estimate the kinetic parameters of oil thermal oxidation. At a β of 10°C/min, the calculated activation energies (E a ) for the blown soybean oil samples investigated ranged between 57.7 and 74.3 kJ/mol for T e1 , 37.6 and 55.3 kJ/mol for T e2 , and 54.7 and 63.0 kJ/mol for T p2 . For comparison, a Z 2 −Z 3 heat-bodied soybean oil sample had activation energies of 72.5, 39.8, and 61.9 for T e1 , T e2 , and T p2 , respectively. By 1H NMR, the amount of allylic and bis-allylic hydrogens present in the blown soybean oil samples relative to an unmodified soybean oil sample was determined to range from 40.3 to 48.2% and 14.9 to 22.4%, respectively.  相似文献   

7.
Beattie R  Bell SE  Borgaard C  Fearon AM  Moss BW 《Lipids》2004,39(9):897-906
Raman spectroscopy has been used to predict the abundance of the FA in clarified butterfat that was obtained from dairy cows fed a range of levels of rapeseed oil in their diet. Partial least squares regression of the Raman spectra against FA compositions obtained by GC showed that good prediction of the five major (abundance >5%) FA gave R 2=0.74–0.92 with a SE of prediction (RMSEP) that was 5–7% of the mean. In general, the prediction accuracy fell with decreasing abundance in the sample, but the RMSEP was <10% for all but one of the 10 FA present at levels >1.25%. The Raman method has the best prediction ability for unsaturated FA (R 2=0.85–0.92), and in particular trans unsaturated FA (best-predicted FA was 18∶1tΔ9). This enhancement was attributed to the isolation of the unsaturated modes from the saturated modes and the significantly higher spectral response of unsaturated bonds compared with saturated bonds. Raman spectra of the melted butter samples could also be used to predict bulk parameters calculated from standard analyzes, such as iodine value (R 2=0.80) and solid fat content at low temperature (R 2=0.87). For solid fat contents determined at higher temperatures, the prediction ability was significantly reduced (R 2=0.42), and this decrease in performance was attributed to the smaller range of values in solid fat content at the higher temperatures. Finally, although the prediction errors for the abundances of each of the FA in a given sample are much larger with Raman than with full GC analysis, the accuracy is acceptably high for quality control applications. This, combined with the fact that Raman spectra can be obtained with no sample preparation and with 60-s data collection times, means that high-throughput, on-line Raman analysis of butter samples should be possible.  相似文献   

8.
A near infrared (NIR) spectroscopic method was developed to measure peroxide value (PV) in crude palm oil (CPO). Calibration standards were prepared by oxidizing CPO in a fermentor at 90°C. A partial least squares (PLS) calibration model for predicting PV was developed based on the NIR spectral region from 1350 to 1480 nm with reference to single-point baseline at 1514 nm. The optimization of calibration factors was guided by the predicted residual error sum of squares test. The standard error of calibration obtained was 0.156 over the analytical range of 2.17–10.28 PV and the correlation coefficient (R 2) was 0.994. The method was validated with an independent set of samples which was prepared in the same manner on a different day. A linear relationship between the American Oil Chemists’ Society and the NIR methods was obtained with R 2 of 0.996 and standard error of performance of 0.17. This study has demonstrated that the prediction of PV in the NIR region is possible. The method developed is rapid, with total analysis time less than 2 min, is environmentally friendly, and its accuracy is generally good for quality control of CPO.  相似文献   

9.
A new, rapid, and direct method was developed for the determination of moisture content in biodiesel produced from various types of oils using Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflectance (ATR) element. Samples of biodiesels used in this study were produced using sludge palm oil (SPO). The calibration set was prepared by spiking double-distilled water into dried biodiesel samples in ratios (w/w) between 0 and 10% moisture. Absorbance values from the wavelength regions 3,700–3,075 and 1,700–1,500 cm−1, and the partial least square (PLS) regression method were used to derive a FTIR spectroscopic calibration model for moisture content in biodiesel samples. The coefficient of determinations (R 2) for the models was computed by comparing the results obtained from FTIR spectroscopy against the values of the moisture concentrations (%) determined using the American Oil Chemists’ Society (AOCS) oven method Ca 2d-25. Same comparison was done using International Union of Pure and Applied Chemistry (IUPAC) distillation method 2.602. R 2 was 0.9793 and 0.9700 using AOCS and IUPAC methods, respectively. The standard error (SE) of calibration was 1.84. The calibration model was cross validated within the same set of samples, and the standard deviation (SD) of the difference for repeatability (SDDr) and accuracy (SDDa) of the FTIR method was determined. With its speed and ease of data manipulation, FTIR spectroscopy is a useful alternative method to other methods for rapid and routine determination of moisture content in biodiesel for quality control.  相似文献   

10.
A rapid method for the quantitative determination of iodine value (IV) of palm oil products by FTIR transmission spectroscopy is described. A calibration standard was developed by blending palm stearin and superolein in specific ratios that covered a range of 27.9 to 65.3 IV units. The spectra of these standards was measured in the range between 3050 and 2984 cm−1, corresponding to the absorption band of=C-H cis stretching vibration. A partial least squares calibration model for the prediction of IV was developed to quantify the IV of palm oil products. A validation approach was used to optimize the calibration with a correlation coefficient of R 2=0.9995 and a standard error of prediction of 0.151. This study concludes that the FTIR transmission approach can be used to determine the IV of palm oil products with a total analysis time per sample of less than 2 min for liquid samples.  相似文献   

11.
The biosynthesis of R-octane-1’3-diol and R-5(Z)-octene-1’3-diol’ two natural antimicrobial agents in apples and pears’ was investigated in stored apples after application of [9’10’12’13-3H]linoleic acid’ [9’10’12’13’15’16-3H]linolenic acid’ [1-14C]linoleic acid’ [U-14C]oleic acid’ lipoxygenase-derived metabolites of [9’10’12’13-3H]linoleic acid’ 13C18-labeled linoleic acid hydroperoxides’ and 2H-labeled octanol derivatives. Analysis of the products and quantification of incorporation and labeling pattern were achieved by high-performance liquid chromatography-radiodetection’ capillary gas chromatography (GC)-isotope ratio mass spectrometry’ and GC-mass spectrometry analysis. Almost all the applied precursors were partly transformed into R-octane-1’3-diol. Linoleic acid derivatives’ still containing the 12’13 cis double bond’ and octanol derivatives oxy-functionalized at carbon 3 were the most efficient precursors of the 1’3-diol. The data imply that R-octane-1’3-diol is generated in stored apples in the course of the β-oxidation from R-3-hydroxy-octanoyl-SCoA originating from 2-cis-octenoyl-SCoA by enoyl-CoA hydratase. In an analogous fashion’ R-5(Z)-octene-1’3-diol is formed from the unsaturated intermediate.  相似文献   

12.
Fourier transform infrared (FTIR) spectroscopy with transmission cell is described to predict anisidine value of palm olein. The calibration set was prepared by mixing the thermally oxidized palm olein and the unoxidized palm olein with certain ratios (w/w) covering a wide range of anisidine values. A partial least square (PLS) regression technique was employed to construct a calibration model. This model was further accomplished by a validation step. The standard error of prediction found was 0.51. The precision of this method was shown to be comparable to the accuracy of the American Oil Chemists’ Society method used for measurement of anisidine value, with coefficient of determination (R 2) of 0.99. The study showed that mid-band FTIR spectroscopy combined with a PLS calibration technique is a versatile, efficient, and accurate technique for the estimation of anisidine value of palm olein within about 2 min with less than 2 mL of sample.  相似文献   

13.
A rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined by the official method of AOCS Tx 1a-66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares (PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions between 3,150 and 990 cm−1 and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained by the AOCS standard method. A correlation coefficient of R 2 = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer, the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation reaction.  相似文献   

14.
The reactions of acetone oxime, a proposed reaction intermediate for the SCR (Selective Catalytic Reduction) of NO with propane on FeZSM-5, have been studied with 13C and 15N solid state MAS NMR (magic angle spinning nuclear magnetic resonance). FeZSM-5 with three different loading levels was prepared by the sublimation method. The thermal reactions of acetone [2-13C] oxime adsorbed on FeZSM-5 samples with different iron loadings were monitored by 13C MAS NMR by heating to the desired temperature and then cooling to room temperature for data acquisition. For the sample with the lowest iron loading (Fe/Al = 0.11), acetic acid and N-methyl-2-propanamine were formed by the decomposition of acetone oxime. For the samples with the higher iron loadings (Fe/Al = 0.69 and 0.91), acetone, N,N-methyl-2,2-propanediamine, and N-methyl-2-propanimine were formed by the decomposition of acetone oxime. 15N MAS NMR was used to investigate reactions of 15NO and acetone oxime on the FeZSM-5 samples. The formation of gas phase N2 and N2O was observed.  相似文献   

15.
A near-infrared (NIR) spectroscopy calibration was developed for the determination of free fatty acids (FFA) in crude palm oil and its fractions based on the NIR reflectance approach. A range of FFA concentrations was prepared by hydrolyzing oil with 0.15% (w/w) lipase in an incubator at 60°C (200 rpm). Sample preparation was performed in Dutch cup, and the spectra were measured in duplicate for each sample. The optimized calibration models were constructed with multiple linear regression analysis based on C=O overtone regions from 1850–2050 nm. The best wavelength combinations were 1882, 2010, and 2040 nm. Multiple correlation coefficients squared (R 2) were: 0.994 for crude palm oil, 0.961 for refined-bleached-deodorized (RBD) palm olein, and 0.971 for RBD palm oil. Calibrations were validated with an independent set of 8–10 samples. R 2 of validation were 0.997, 0.943, and 0.945, respectively. The developed method was rapid, with a total analysis time of 5 min, and environmentally friendly, and its accuracy was generally good for raw-material quality control.  相似文献   

16.
A new method was developed to determine the gossypol content in cottonseed oil using FTIR spectroscopy with a NaCl transmission cell. The wavelengths used were selected by spiking clean cottonseed oil to gossypol concentrations of 0–5% and noting the regions of maximal absorbance. Transmittance values from the wavelength regions 3600–2520 and 1900–800 cm−1 and a partial least squares (PLS) method were used to derive FTIR spectroscopic calibration models for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils. The coefficients of determination (R 2) for the models were computed by comparing the results from the FTIR spectroscopy against those obtained by AOCS method Ba 8-78. The R 2 were 0.9511, 0.9116, and 0.9363 for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils, respectively. The SE of calibration were 0.042, 0.009, and 0.060, respectively. The calibration models were cross-validated within the same set of oil samples. The SD of the difference for repeatability and accuracy of the FTIR method were better than those for the chemical method. With its speed (ca. 2 min) and ease of data manipulation, FTIR spectroscopy is a useful alternative to standard wet chemical methods for rapid and routine determination of gossypol in process and/or quality control for cottonseed oil.  相似文献   

17.
Ayyildiz HF  Kara H  Sherazi ST 《Lipids》2011,46(12):1181-1190
A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD < 1%), and were rugged when the method was performed by a different analyst. The linear concentration range was calculated as 0.09–1.50 and 0.07–1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 × 10−4–2.28 × 10−3 oleic acid % and 7.11 × 10−4–2.23 × 10−3 oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.  相似文献   

18.
A convenient method was developed for preparation of FAME in small amounts from glycerolipids of blood or breast milk. Initially, 0.04–0.06 mL blood or breast milk was spotted onto a small piece of filter paper (1.5×1.5 cm) that had been washed with acetone containing 0.05% 2,6-di-tert-butyl-p-cresol (BHT). Fach piece, once it had dried, was put in a small test tube, to which 2 mL hexane and 0.2 mL 2 M KOH/methanol were added. After vigorous mixing or sonication for 2 min at room temperature, the solution was neutralized or acidified by the addition of a few drops of acetic acid. To the solution was added 2 mL H2O, and then the hexane layer that separated was concentrated to dryness in vacuo. The FAME obtained were analyzed by GC. The method was applicable to the analysis of a large number of blood and breast milk samples, and the arachidonate/(eicosapentaenoate +docosahexaenoate) ratios could be determined rapidly.  相似文献   

19.
Monoterpenes such as limonene and perillyl alcohol (PA) are currently under investigation for their chemotherapeutic properties which have been tied to their ability to affect protein isoprenylation. Because PA affects the synthesis of isoprenoids’ such as ubiquinone’ and cholesterol is the end product of the synthetic pathway from which this isoprenoid pathway branches’ we investigated the effects of this compound upon cholesterol metabolism in the colonic adenocarcinoma cell line SW480. PA (1 mM) inhibited incorporation of 14C-mevalonate into 21–26 kDa proteins by 25% in SW480 cells. Cholesterol (CH) biosynthesis was assessed by measuring the incorporation of 14C-acetate and 14C-mevalonate into 27-carbon-sterols. Cells treated with PA (1 mM) exhibited a fourfold increase in the incorporation of 14C-acetate but not 14C-mevalonate into cholesterol. Mevinolin (lovastatin)’ an inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase’ at 2 μM concentration’ inhibited CH synthesis from 14C-acetate by 80%. Surprisingly’ concurrent addition of mevinolin and PA did not significantly alter the stimulatory effects of PA. As observed differences in 14C-acetate and 14C-mevalonate precursor labeling could indicate PA affects early pathway events’ the effects of this monoterpene on HMG-CoA reductase activity were evaluated. Unexpectedly’ 1 mM PA did not stimulate activity of this enzyme. Consistent with its action as a reversibly bound inhibitor’ in washed microsomes’ 2 μM mevinolin pretreatment increased reductase protein expression causing a 12.7 (±2.4)-fold compensatory HMG-CoA reductase activity increase; concurrent treatment with 1 mM PA attenuated this to a 5.3 (±0.03)-fold increase. Gas chromatographic analysis confirmed CH was the major lipid present in the measured thin-layer chromatography spot. Since 14C-acetate incorporation into free fatty acid and phospholipid pools was not significantly affected by PA treatment’ nonspecific changes in whole acetate pool sizes were not indicated. Because increases in endogenous CH synthesis should result in compensatory changes in exogenous sterol utilization’ the effects of PA upon low density lipoprotein (LDL) receptor activity were evaluated. Consistent with the observed increases in CH synthesis’ 1 mM PA decreased 125I-LDL internalization to 50% of the fetal bovine serum control; concurrent addition of 2 μM mevinolin attenuated this effect to a reduction of 80% of the control value. Data suggest that in certain colonic tumor cells PA strongly affects cholesterol metabolism via a mechanism of action that is insensitive to the HMG-CoA reductase inhibitor mevinolin.  相似文献   

20.
The seeds of four prairie fruits—chokecherry (Prunus virginiana), thorny buffaloberry (Shepherdia argentea), Woods’ rose (Rosa woodsii) and hawthorn (Crataegus × mordenensis)—from Southern Alberta were investigated. The lipid contents of the seeds were found to be 10.4, 11.5, 3.7 and 3.4%, respectively. The tested seed lipids contained mainly linoleic acid in the range from 27.9 to 65.6% and oleic acid from 19.7 to 61.9%. The thorny buffaloberry and Woods’ rose seed lipids contained 29.2 and 30.8% of linolenic acid, respectively. The contents of palmitic and stearic acids ranged from 3.2 to 5.4% and 1.6 to 2.2%, respectively. The contents of total tocopherols in the chokecherry, thorny buffaloberry, Woods’ rose and hawthorn seed lipids accounted for 595, 897, 2,358 and 2,837 mg/kg, respectively. The main sterols in the lipids were β-sitosterol, Δ5-avenasterol, cycloartenol, campesterol, stigmasterol and gramisterol. The results of the present study show that the lipids from the seeds of the investigated prairie fruits could be a good source of valuable essential fatty acids, tocopherols and sterols, thus suggesting their application as functional foods and nutraceuticals.  相似文献   

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