Collaborative test of determination of iodine value in fish oils. 2. Carbon tetrachloride or cyclohexane/acetic acid as solvents

Nine laboratories participated in a collaborative test to determine the iodine value (IV) of eight samples of fish oil (four with IV<150; four with IV>150) with either carbon tetrachloride (AOCS Official Method Cd 1–25) or cyclohexane/acetic acid (AOCS Recommended Practice Cd 1d-92) as solvent and 1 h of reaction time. Laboratories received coded duplicate samples (hidden duplicates) and carried out duplicate determinations on each oil by each method (open duplicates). Replacing carbon tetrachloride with cyclohexane/acetic acid resulted in similar mean values for both low- and high-IV oils and similar estimates of repeatability and reproducibility. The repeatability standard deviation (s _r ), based on hidden duplicates, with carbon tetrachloride and cyclohexane/acetic acid were 1.71 and 1.55, respectively. The corresponding reproducibility standard deviations were 1.81 and 1.98.     

Collaborative test of determination of iodine value in fish oils. 1. Reaction time and carbon tetrachloride or cyclohexane as solvents

Twenty-two laboratories participated in a collaborative test to determine the iodine value (IV) of eight samples of fish oil (four with IV<150, four with IV>150) with either carbon tetrachloride (AOCS Official Method Cd 1–25) or cyclohexane (AOCS Recommended Practice Cd 1b-87) as solvent and either 1 or 2 h of reaction time. Laboratories received coded duplicate samples (hidden duplicates) and carried out duplicate determinations on each oil by each solvent-time combination (open duplicates). Replacing carbon tetrachloride with cyclohexane resulted in a lower IV (P<0.001). The decrease averaged 1.6 IV units for low-IV oils and 3.8 IV units for high-IV oils; this difference in response of 2.2 IV units between low- and high-IV oils was significant (P<0.001). Increasing the reaction time had a relatively small effect (0.34±0.18). There was no interaction of reaction time with solvent or oil type. Cyclohexane caused emulsions, which made it difficult to titrate residual iodine and thus increased the variability of the determination. The repeatability standard deviations (s _r ), based on hidden duplicates, for 1-h reaction time with carbon tetrachloride and cyclohexane were 2.17 and 3.35, respectively. The corresponding reproducibility standard deviations were 2.73 and 4.53.     

Determination of trans fatty acids in hydrogenated vegetable oils by attenuated total reflection infrared spectroscopy: Two limited collaborative studies

An attenuated total reflection infrared spectroscopy procedure was collaboratively studied among two sets of five laboratories for quantitating the total trans fatty acid levels in neat (without solvent) hydrogenated vegetable oils, measured as triacylglycerols in one study, and as fatty acid methyl ester derivatives in the other. Unlike the fatty acid methyl esters, the triacylglycerols required no derivatization but had to be melted prior to measurement. To obtain a symmetric absorption band at 966 cm⁻¹ on a horizontal background, the single-beam spectrum of the trans-containing fat was "ratioed" against that of a refined oil or a reference material that contained only cis double bonds. A single-bounce horizontal attenuated total reflection cell that requires 50 μL of undiluted test samples was used for oils, melted fats, or their methyl esters. For fatty acid methyl esters, the reproducibility relative standard deviations were in the range of 0.9 to 18.46% for 39.08 to 3.41% trans, determined as methyl elaidate per total fatty acid methyl esters. For five pairs of triacylglycerol blind duplicates, the reproducibility and repeatability relative standard deviations were in the ranges of 1.62 to 18.97%, and 1.52 to 13.26%, respectively, for 39.12 to 1.95% trans, determined as trielaidin per total triacylglycerols. Six pairs of spiked triacylglycerol blind duplicates (quality assurance standards) exhibited high accuracy in the range of 0.53 to 40.69% trans and averaged a low bias of 1.3%. These statistical analysis results were compared to those collaboratively obtained by the recently adopted AOCS Cd14-95 and AOAC 994.34 Infrared Official Methods.     

Near-infrared reflectance measurement of moisture,protein and oil content of ground crambe seed

Crambe moisture, protein and oil percentages were predicted by fixed-filter near-infrared reflectance with standard errors of prediction (SEP) of 0.26, 0.59 and 0.86 percentage points, respectively. Crambe had a large range of protein and oil percentages, 17.4%–25.0% and 17.7%–36.4% respectively. Calibration samples were selected on the basis of relative spectral data, with no advance knowledge of protein and oil content. This procedure selected samples representing the full range of constituent values, and resulted in calibrations that had lower SEP's than standard errors of calibration.     

Determination of phosphorus in edible oils by inductively coupled plasma—Atomic emission spectrometry and oil-in-water emulsion of sample introduction

The determination of phosphous was carried out using emulsion sample preparation followed by analysis by inductively coupled plasma-atomic emission spectrometry. The optimal oil-in-water (o/w) emulsion and surfactant concentrations were found by applying response surface methodology. Two phosphorus emission lines were tested. Ethoxynonylphenol was a good choice for the emulsion preparation. The optimal concentration for the oil in the o/w emulsion and the surfactant concentrations were ca. 8.0–37% w/w and ca. 1.0–10% w/w ethoxynonylphenol, respectively, for the 213.620 nm line; and an oil phase emulsion concentration between ca. 18–32% w/w and ca. 3–8% w/w ethoxynonylphenol for the 214.911 nm emission line. Good agreement was found between calibration curves for emulsified aqueous standards solutions and o/w emulsions. The use of aqueous standards for calibration purposes is a good addition in the analysis of this type of oil sample where certified standards are not available. Recoveries ranged from 98 to 105% and from 102 to 116% for the 213 and 214 nm lines, respectively with relative standard deviations lower than 7%.     

Determination of the Unsaponifiable Matter in Fatty Acids by a Rapid Column Method

A rapid, quantitative method for determining the unsaponifiable matter (USM) of commercial fatty acids is described. The fatty acid samples are saponified with a mixture of potassium hydroxide and Celite 545 ground together then heated for a short period. The resulting granular powder is transferred to a glass chromatography column containing a short section of CaCl₂/Celite mixture, and the USM is eluted with dichloromethane. Samples were analyzed in 2 separate laboratories by the new method with slight variations. Good agreement between duplicates and between laboratories was obtained for all of the acids examined. Samples were also analyzed by Official Methods, and the results were uniformly somewhat higher by the proposed method. Agricultural Research Service, U.S. Department of Agriculture.     

Soybean seed protein and oil contents and fatty acid composition adjustments by drought and temperature

Environmental stress during soybean [Glycine max (L.) Merr.] seed fill can alter the chemical composition of the seed and reduce yield, viability, and vigor. The effect of drought and high air temperature (AT) on soybean seed protein and oil contents have not been reported. The objective of this study was to characterize the protein and oil contents and fatty acid composition of soybean seeds after exposure to drought and high AT during seed fill. Experiments were conducted during two years, in which three drought-stress levels were maintained throughout seed fill. In Experiment I, “Gnome” soybeans were grown at daytime AT of 20 and 26°C, and in Experiment II “Hodgson 78” were grown at 27, 29, 33, and 35°C. Across experiments, severe drought increased protein content by 4.4 percentage points, while oil content decreased by 2.9 percentage points. As drought stress increased, measured by accumulating stress degree days, protein content increased linearly and oil content decreased linearly at each AT. Seeds from plants exposed to 35°C during seed fill contained 4.0 percentage points more protein and 2.6 percentage points less oil than those exposed to 29°C when averaged across drought stress levels. Drought had little effect on the fatty acid composition of the oil, but high AT reduced the proportion of the polyunsaturated components.     

Proficiency test on the determination of mineral oil in sunflower oil

Following the discovery of mineral oil contamination of Ukrainian sunflower oil in April 2008, the Institute for Reference Materials and Measurements (IRMM) of the European Commission's Joint Research Centre (JRC) was requested by the Directorate General Health and Consumers (DG SANCO) to organise a proficiency test on the determination of mineral oil in sunflower oil. The aim of this test was to evaluate the comparability of analysis results gained by laboratories in the EU and the Ukraine. The organisation of the study and the evaluation of the results were done in accordance with “The International Harmonised Protocol for the Proficiency Testing of Analytical Chemistry Laboratories” and ISO Guide 43. Altogether 62 laboratories from 19 EU member states, Switzerland and the Ukraine subscribed for participation in the study. Four test samples at concentration levels between about 100 and 350 mg/kg, comprising contaminated crude sunflower oil, contaminated refined sunflower oil, and spiked sunflower oil, and a solution of mineral oil in n‐heptane were dispatched to the participants. The participants were asked to determine the mineral oil content of the test samples by application of their in‐house analysis methods. In total, 55 sets of results were reported to the organisers of the study. The performance of laboratories was expressed by z‐scores for the oil samples and by relative bias for the mineral oil solution in n‐heptane. The percentage of successful laboratories in the determination of the mineral oil content of sunflower oil was for all sunflower oil test materials about 80%.     

Analysis and fatty acid composition of tobacco seed oils

Summary THE fatty acid compositions of twelve samples of oil representing a number of different types and varieties of tobacco were determined by the thiocyanometric method. The samples were remarkably uniform in composition, containing on the average 75% linoleic, 15% oleic, and 10% saturated acids. Spectrophotometric determination of the linoleic acid content of two samples of oil gave values 3.0 and 5.4% higher than those by the thiocyanometric method. A more complete investigation of the fatty acid constituents of one sample of flue-cured tobacco seed oil was carried out by analysis of fractions obtained by distillation of the methyl esters and by low-temperature crystallization of the distilled ester fractions. The composition calculated from these analyses agreed well with that determined from analysis directly on the oil. The saturated acids consisted of palmitic and stearic acids, the proportions being about 7 and 3%, respectively, of the total fatty acids. Analysis of this sample of oil showed that it contained 0.043% of tocopherol. From its composition, tobacco seed oil would seem to be particularly suitable for the manufacture of nonyellowing alkyds or for the preparation of technical linoleic acid. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.     

Dilatometric investigations of fats II. Dilatometric behavior of some plastic fats between 0° C. and their melting points

Summary 1. Dilatometric curves between 0°C. and their melting points have been obtained for the following fats: lard, butterfat, cottonseed oil, peanut oil, a commercial margarine oil, a commercial all-hydrogenated vegetable shortening, three samples of soybean oil hydrogenated to different degrees, a hard butter fractionally crystallized from hydrogenated peanut oil, a mixture of tristearin and soybean oil, and a synthetic fat containing equal molar proportions of stearic and oleic acids. 2. The dilatometric curves, of volume change in the fat against temperature, were in every case composed of a series of straight lines, separated by sharp breaks or transition points. 3. The number of linear sections in the dilatometric curves corresponded in a general way with the known degree of complexity in the glycerides of the fats, and varied from two in the case of the relatively simple stearic-oleic glyceride mixture, to at least seven in the case of the all-hydrogenated shortening. Since each break in the curve must correspond to the disappearance of a distinct class of solid glycerides or glyceride complexes, the application of dilatometry to the qualitative and quantitative determination of glyceride composition in fats is suggested. 4. Only two of the fats examined, the mixture of tristearin and soybean oil, and the synthetic stearicoleic glyceride mixture, exhibited polymorphism, even after rapid solidification in ice water. Presented before the American Oil Chemists’ Society Meeting, New Orleans, Louisiana, May 10 to 12, 1944. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Regulatory Infrared Spectroscopic Method for the Rapid Determination of Total Isolated Trans Fat: A Collaborative Study

Using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, collaborating scientists in ten different laboratories measured (in duplicate) the total trans fat content of ten fat or oil test samples, two of which were blind duplicates. The procedure used entailed measuring the height of the negative second derivative of the IR absorption band at 966 cm^?1. This absorption is attributed to the C?CH deformation vibration that is characteristic of isolated (non-conjugated) double bonds with the trans configuration. The precision of ATR-FTIR results in this international collaborative study was satisfactory and led to the approval of this validated procedure as official method AOCS Cd 14e-09 in late 2009. This official method is also suitable for analysis of total isolated trans fat and oil products containing, or supplemented with, trans conjugated linoleic acid (CLA) isomers. Although this method does not require derivatization of the oil or fat test materials, as required for GC, fats and oils in foods must be extracted with organic solvents before analysis. This method is also rapid (5 min) and does not require any weighing or quantitative dilution of unknown neat fat or oil test samples in any solvent. The AOCS Cd 14e-09 method is suitable for determination of test samples with zero trans fat, which is defined according to the US labeling regulations as 0.5 g trans fat per serving or 1.8% trans fat, as a percentage of total fat.     

Oil determination of oilseed. Gravimetric routine method

Summary A new method for the determination of oil on long series of oilseed is presented. It is a gravimetric method which reduces the hand labor to a minimum. Testing this method on a series of pure samples of oilseed, which were analyzed for five days with two analyses on each sample every day, the standard deviation for a single analysis lay within 0.30% and for the average of two duplicates within 0.27% of oil. The difference between averages for the new method and averages of extraction analyses made with continuous extractors did not exceed 0.28% of oil.     

Virgin-Olive-Oil Color in Relation to Sample Thickness and the Measurement Method

Color changes of virgin-olive-oil samples contained in cells with different thicknesses were analyzed. Ten different commercial virgin olive oils were measured at different sample thicknesses by two methods: conventional spectrophotometry (5.0, 10.0, and 50.0 mm path length cells), and spectroradiometry (cylindrical cells with 8.0, 11.2, 15.6, 19.6, 23.2, 27.2, 36.8 and 46.4 mm internal diameters) with samples placed on the floor of a commercial cabinet using a standard daylight source. The illumination in these two methods was different, resulting in notable color differences in the samples. Color variations of virgin olive oils depending on thickness do not follow the same trend for all samples. Neither the Bouguer-Lambert-Beer law nor the Kubelka-Munk theory provided successful color predictions in the whole range of thicknesses considered here. We can conclude that for precise and reproducible color measurements of virgin-olive-oil color, it is necessary to fix both the thickness of the sample and the illumination geometry. To achieve an easier communication between industries and/or consumers, we propose that virgin-olive-oil color be measured using a spectrophotometer with 5.0-mm path length cells, for three reasons: conventional olive-oil laboratories have spectrophotometers more often than spectroradiometers; with virgin olive oils the cleaning of 5.0 mm cells is easier than for 1.0 mm cells and it does not consume a large amount of oil; spectrophotometric signals for 5.0-mm path length cells allow reliable measurements of even the darkest virgin-olive-oil samples.     

Iron accumulation in oil during the deep-fat frying of meat

Iron accumulation in oil is a potential problem when frying food containing substantial amounts of iron. Selected meat products (skinless chicken breast, beef liver, and lean beef) were ground and fried (ca. 2-cm spheres, ca. 10 g/sphere) in partially hydrogenated soybean oil (PHSBO). Samples (450 g) of ground meat were fried 3 times/h for 8 h/d for 3 d. Oil samples were collected for analysis for iron (every 8 h) and oil degradation (every 4 h) and replaced with fresh oil. The iron contents of oil samples after 3 d of frying were approximately 0.11, 0.48, and 4.01 mg of iron/kg of PHSBO for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in color and an increased tendency to foam for the beef liver oil sample compared with the other samples. After frying, the acid values were 0.9, 1.1, and 1.4 for the oil samples for chicken, beef, and liver, respectively. After frying, the p-anisidine values were 11.5, 12.8, and 32.6 for the oil samples for chicken, beef, and liver, respectively; the food oil sensor values were 0.96, 0.96, and 0.83 for the oil samples for chicken, beef, and liver, respectively.     

Oil and water analysis of sunflower seed by near-infrared reflectance spectroscopy

The applicability of NIR for oil and moisture analyses of sunflower seed was determined using a NIR spectrocomputer system. The method was compared with the wide-line NMR method for oil analysis and with the A.O.C.S. oven method for moisture analysis. The NIR was calibrated with 120 samples for oil (96 for calibration, 24 for prediction) and 63 samples for moisture (55 for calibration, 8 for prediction). Twenty-two sunflower seed samples were analyzed for oil and moisture by NIR and by methods used by industry. The oil contents of the samples by NMR and NIR were not significantly different. The overall mean oil contents and mean of the standard deviations for the samples were: NMR, 44.2%±0.35% and NIR, 44.34%±0.74%. A significant difference was found between the moisture values obtained by the oven-drying method and NIR. The average standard deviation for moisture by NIR was 0.57% compared with 0.07% for the oven-drying method. The variability of the oil content in one of the commercial seed samples was 1.52% oil as determined by NMR and 2.52% as determined by NIR. The advantages and disadvantages of both methods are discussed.     

The isolation of pyrolysis oil from castor seeds via a Low Temperature Conversion (LTC) process and its use in a pyrolysis oil-diesel blend

A Low Temperature Conversion (LTC) process carried out on a sample of castor seeds, Ricinus communis, generated fractions of pyrolysis oil, pyrolitic char, gas and aqueous extracts in the following relative amounts, respectively: 50%, 28%, 10% and 12% [w/w]. The pyrolysis oil was added at loadings of 2%, 5%, 10%, 20% and 30% [w/w] to commercial diesel. The density, viscosity, sulfur content, glow point, volatility and cetane index of these mixtures were determined. The results indicate that the addition of pyrolysis oil to commercial diesel results in fuel mixtures within the norms of ANP diesel directive no 15, made on 19. 7. 2006, with the exception of the 20% mixture (which has an unfavorable viscosity) and the 30% mixture (which has an unfavorable viscosity and volatility).     

碱源/氟体系Ti-MWW分子筛的合成

使用不同的碱源(氨水、己二胺和三乙醇胺)替代合成Ti-MWW分子筛所用40%的模板剂哌啶,并添加适量的氟化氢铵作为矿化剂。所得的样品通过XRD、UV-Vis、FT-IR和SEM进行表征分析,并考察不同碱源替代合成Ti-MWW分子筛在过氧化氢为氧化剂丙烯醇环氧化反应中的催化性能。结果表明,使用不同碱源合成的Ti-MWW分子筛均具有良好的MWW拓扑结构。相比于常规方法合成的Ti-MWW分子筛,氨水为碱源时,丙烯醇转化率增加了12个百分点,选择性下降了1个百分点;三乙醇胺作为碱源时,丙烯醇转化率增加了2.9个百分点,缩水甘油选择性上升5.5个百分点。采用三乙醇胺为碱源合成的Ti-MWW分子筛显著提高了缩水甘油选择性。     

Physical Characteristics of Peanut Butter Influenced by Fully Hydrogenated Flixweed Seed Oil (Descurainia sophia L.) as a Stabilizer

The functional benefits provided by flixweed seed oil (FSO) warrant its application as an alternative to current commercial stabilizers used in peanut butter. The extracted FSO was fully hydrogenated and added to the lab‐made peanut butter in quantities of 1, 1.5, and 2 % (w/w). Samples were stored at 4, 21, and 40 °C, and tested at 2, 6, 16, and 24 weeks for oil separation tests and texture characteristics including hardness, adhesiveness, cohesiveness, and gumminess. Fully hydrogenated flixweed seed oil (FHFO) improved the oil holding capacity of peanut butter at 1, 1.5 and 2 % (w/w). Peanut butter containing FHFO, at a quantity of 2 % (w/w), showed the least oil separation and had comparable or less oil separation than the sample containing 1.5 % commercial stabilizer. Other physical properties were comparable between these two samples.     

Physical characteristics of mustard oil solvent miscella

During commercial solvent extraction of oil from an oil-seed, it is necessary to determine oil content in the miscella, drawn intermittently from the extractor, to obtain an overall extraction rate. We measured optical density, specific gravity, refractive index and viscosity of miscella of different known oil concentrations. These four characteristics were measured by calculating deviations from the actual values. The deviations were maximum for optical density, intermediate for specific gravity and viscosity, and small for refractive index, suggesting the latter to be an appropriate rapid method of determining miscella oil content.     

Comparison of the whole fruit and component methods of analysis of tung fruit

Summary The effect of moisture content and fineness of grinding on the percentages of oil extracted by the whole fruit method were investigated and the results compared with those obtained by the component method. The spacing of the plates on the Bauer laboratory mill used for grinding whole tung fruit for oil analysis was found not to be critical within certain narrow limits. No differences were found in the oil content when samples of fruit were ground with plate spacings from 0.004 inch to 0.012 inch, but the results were lower with plate spacings of 0.020 inch. No difference was found in the percentages of oil obtained by the component and the whole fruit methods when the results were calculated on the basis of the original moist sample and no correction had to be applied in the calculation of the results by the whole fruit method. The average percentage of moisture obtained by the two methods differ, consequently care must be used in comparing oil contents calculated to a moisture-free basis since the differences in moisture content will be reflected in the values for the apparent oil content. Careful analyses of tung fruit by either the whole fruit or the component method yield reliable results over a wide range of moisture content although in the case of the component method unusually wet kernels (above 10% moisture) must be partially dried before regrinding in a mortar and pestle during the extraction operation. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.