Wax composition of sunflower seed oils

Waxes are natural components of sunflower oils, consisting mainly of esters of FA with fatty alcohols, that are partially removed in the winterization process during oil refining. The wax composition of sunflower seed as well as the influence of processing on the oil wax concentration was studied using capillary GLC. Sunflower oils obtained by solvent extraction from whole seed, dehulled seed, and seed hulls were analyzed and compared with commercial crude and refined oils. The main components of crude sunflower oil waxes were esters having carbon atom numbers between 36 and 48, with a high concentration in the C₄₀−C₄₂ fraction. Extracted oils showed higher concentrations of waxes than those obtained by pressing, especially in the higher M.W. fraction, but the wax content was not affected significantly by water degumming. The hull contribution to the sunflower oil wax content was higher than 40 wt%, resulting in 75 wt % in the crystallized fraction. The oil wax content could be reduced appreciably by hexane washing or partial dehulling of the seed. Waxes in dewaxed and refined sunflower oils were mainly constituted by esters containing fewer than 42 carbon atoms, indicating that these were mostly soluble and remained in the oil after processing.     

Separation of wax esters from olive oils by high-performance liquid chromatography

To detect adulteration of olive oil with solvent-extracted oils, the determination of the wax ester content has become more important during recent years. Hence, a greater number of wax ester analyses need to be performed by quality control laboratories. The most common method in use requires a liquid chromatographic (LC) separation of the less polar fraction, which contains the wax esters, from the glyceride matter on a hand-filled silica gel column. The aim of this project was to verify the possibility of replacing LC with high-performance liquid chromatography by taking advantage of the greater reliability and repeatability of this technique, as well as of the possibility of making the separation automatic. The paper describes how to perform the analysis and the statistical test that was carried out; furthermore, a comparison has been made with the usual method and results are in good agreement.     

Kinetics of catalytic transfer hydrogenation of some vegetable oils

Catalytic transfer hydrogenation of corn, peanut, olive, soybean, and sunflower oils has been studied with aqueous sodium formate solution as hydrogen donor and palladium on carbon as catalyst. Kinetic constants and selectivity have been determined under intensive stirring in the presence of stabilizing agents. Hydrogenation reactions followed first-order kinetics with respect to fatty acids. Besides good selectivity and short reaction time, this method offers safe and easy handling. The presence of linolenic acid retards the migration of double bonds, which explains why soybean oil is the most appropriate for this hydrogenation process.     

Determination of mixtures in vegetable oils and milk fat by analysis of sterol fraction by gas chromatography

A rapid gas-chromatographic (GC) procedure was developed for the analysis of the total sterol fraction of vegetable oils, milk fat or mixtures, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk fat. The method, which employs alkali-catalyzed transesterification with KOH/methanol, was compared with saponification procedures with and without transformation of sterols into silyl derivatives prior to analysis. Repeatability of the method was assessed, and the coefficient of variation was 6.0 and 8.0% for β-sitosterol in olive and sunflower oils, respectively. Recovery of β-sitosterol ranged from 92.6 to 95.8 for both oils. The GC method assayed in this work requires little analysis time and eliminates the need for saponification, extraction, and derivatization steps. It offers good repeatability and recovery and is thus well suited to routine use.     

AOCS collaborative study on sensory and volatile compound analyses of vegetable oils

An AOCS collaborative study was conducted to determine the effectiveness of sensory analysis and gas chromatographic analyses of volatile compounds in measuring vegetable oils for levels of oxidation that ranged from none to high. Sixteen laboratories from industry, government, and academia in Canada and the United States participated in the study to evaluate the flavor quality and oxidative stability of aged soybean, corn, sunflower, and canola (low-erucic acid rapeseed) oils. Analytical methods included sensory analyses with both flavor intensity and flavor quality scales and gas-chromatographic volatiles by direct injection, static headspace, and dynamic headspace (purge and trap) techniques. Sensory and volatile compound data were used to rank each of the oils at four levels of oxidation—none, low, moderate, and high. For soybean, canola, and sunflower oils, 85–90% of laboratories correctly ranked the oils by either analysis. For corn oil, only 60% of the laboratories ranked the samples according to the correct levels of oxidation by either analysis. Variance component estimates for flavor scores showed that the variation between sensory panelists within laboratories was lowest for the unaged oils. As storage time increased, the variance also increased, indicating that differences among panelists were greater for more highly oxidized oils. Between-laboratory variance of sensory panel scores was significantly lower than within-laboratory variance.     

Effect of randomization on oxidative stability of vegetable oils at two different temperatures

Five vegetable oils were each randomized by chemical means (with the use of a sodium potassium alloy) and by enzymatic means (using a nonspecific lipase). The success of the randomization procedure was confirmed via positional analysis. The oxidative stabilities of the native and chemically randomized oils were determined at storage temperatures of 28°C and 55°C using absorbance at 234 nm as indicative of conjugated diene content. No difference between curves occurred in oils stored at 55°C, however, at the lower temperature all chemically randomized oils had significantly steeper slopes (P<0.05), suggesting a lower stability. When both enzymatically and chemically randomized oils were compared to native oils at 28°C, no significant difference occurred between slopes of native and enzymatically randomized oils, however, the end content of conjugated dienes was significantly higher for chemically randomized canola, corn and soybean oils (P<0.05). No difference was seen between the slopes of the three different oils from either linseed or sunflower. Since both of these oils exhibited higher oxidation rates, it is possible that observation of differences between the stability of native and chemically randomized oild is dependent upon the rate of the reaction.     

Analysis of triacylglyceride hydroperoxides in vegetable oils by nonaqueous reversed-phase high-performance liquid chromatography with ultraviolet detection

Triacylglyceride hydroperoxides (HPO-TAG), the primary autoxidation products of triacylglycerides (TAG), have been analyzed in polyunsaturated vegetable oils by means of nonaqueous reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet detection. Using a retention time model based on equivalent carbon numbers, mono- and bishydroperoxy TAG and hydroxy TAG could be identified. The correlation between the peroxide value (POV) determined by iodometric titration and quantitative HPLC results for HPO-TAG was established for sunflower oil samples with POV between 0.5 and 50 meq/kg. The recovery of HPO-TAG in the HPLC procedure was found to be close to 100% in the POV range of 4 to 71 meq/kg. Absolute quantitative results for HPO-TAG in sunflower oil samples could not be obtained accurately, as molar extinction coefficients of HPO-TAG occurring in natural oils deviate from those of available HPO-TAG reference compounds.     

Characteristics of tea seed oil in comparison with sunflower and olive oils and its effect as a natural antioxidant

A comparison of iodine values showed that the degree of saturation of tea seed oil (Lahjan variety) was intermediate between the oils of sunflowerseed (Fars variety) and olive (Gilezeytoon variety), and the saponification values of these three oils were similar. Tea seed oil consisted of 56% oleic acid (C18∶1), 22% linoleic acid (C18∶2), 0.3% linolenic acid (C18∶3), and therefore, on the basis of oleic acid, occupied a place between sunflower and olive oil. In studies at 63°C, the shelf life of tea seed oil was higher than that of sunflower oil and similar to olive oil. Tea seed oil was found to have a natural antioxidant effect, and it enhanced the shelf life of sunflower oil at a 5% level. In this study, tea seed oil was found to be a stable oil, to have suitable nutritional properties (high-oleic, medium-linoleic, and lowlinolenic acid contents), and to be useful in human foods.     

Assessment of olive oil adulteration by reversed-phase high-performance liquid chromatography/amperometric detection of tocopherols and tocotrienols

A method involving reversed-phase high-performance liquid chromatography with amperometric detection has been developed for the analysis of tocopherols and tocotrienols in vegetable oils. The sample preparation avoids saponification. Recoveries of α-tocotrienol and γ-tocotrienol in extra virgin olive oil were 97.0 and 102.0%, respectively. No tocotrienols were detected in olive, hazelnut, sunflower, and soybean oils, whether virgin or refined. However, relatively high levels of tocotrienols were found in palm and grapeseed oils. This method could detect small quantities (1–2%) of palm and grapeseed oils in olive oil or in any tocotrienol-free vegetable oil and might, therefore, help assess authenticity of vegetable oils.     

Design and operation of a modified silica gel column chromatography

Liquid–solid chromatography (LSC) is the oldest of the various liquid chromatography methods. Despite the fact that high-performance liquid chromatography (HPLC) operation leads to better separation and analysis, classical column chromatography and thin-layer chromatography (TLC) are still widely practiced because of their convenience. In this study, a modified silica gel column chromatography was designed with the objective of reducing the amount of solvent required to achieve the same degree of separation as the classical silica gel column chromatography. The separation of squalene and fatty acid steryl esters (FASEs) from non-polar lipid fraction (NPLF) of soybean oil deodorizer distillate (SODD) was employed as a model system to test the effectiveness of this new design. Modified silica gel column chromatography process is feasible from economic point of view compare to classical silica gel column chromatography because it significantly reduces the amount of solvent and time required to achieve the same degree of separation. By employing modified silica gel column chromatography to obtain the squalene-rich fraction, the mobile phase volume and elution time required as fractions of those needed in classical silica gel column chromatography are 1/73 and 1/18, respectively. To obtain the FASEs-rich fraction, the corresponding mobile phase volume and elution time are 1/221 and 1/23, respectively of those needed in classical silica gel column chromatography.     

Quantitative determination of diesel oil in contaminated edible oils using high-performance liquid chromatography

A simple and reliable high-performance liquid chromatography method for the analysis of diesel oil in contaminated edible oils is described. Analysis performed using a diol column with a mobile phase of heptane and isopropanol (94∶6, vol/vol). Although baseline separation between diesel and other background fluorescent components was not achieved, quantitation was still possible using baseline integration. The method is linear over the range of 5–1000 μg/g with a correlation coefficient (r ²) of 0.9984. Average recoveries from spiked edible oils were 94.4–101.3%, with a limit of quantitation (LOQ) of 5 μg/g for sunflower oil, palm olein, and groundnut oil. Corn oil has a higher content of ester components, thus, LOQ was slightly worse (40 μg/g). The applicability of the method was confirmed by gas chromatography-mass spectroscopic detection to show the presence of diesel hydrocarbons in the suspected contaminated crude palm oil. This procedure provides a simple and sensitive method for determining diesel oil concentration in contaminated edible oils without prior sample cleanup or extraction.     

The triacylglycerol structure of olive oil determined by silver ion high-performance liquid chromatography in combination with stereospecific analysis

The compositions of positionssn-1,sn-2 andsn-3 of triacylglycerols from “extra-virgin” olive oil (Olea europaea) were determined. The procedure involved preparation of diacyl-rac-glycerols by partial hydrolysis with ethyl magnesium bromide; 1,3-, 1,2- and 2,3-diacyl-sn-glycerols as (S)-(+)-1-(1-naphthyl)ethyl urethanes were isolated by highperformance liquid chromatography (HPLC) on silica, and their fatty acid compositions were determined. The same procedure was also carried out on the five main triacylglycerol fractions of olive oil after separation according to the degree of unsaturation by HPLC in the silver ion mode. Although stereospecific analysis of the intact triacyl-sn-glycerols indicated that the compositions of positionssn-1 andsn-3 were similar, the analyses of the molecular species demonstrated marked asymmetry. The data indicate that the “1-random, 2-random, 3-random” distribution theory is not always applicable to vegetable oils.     

Fast quantitative analysis of soybean oil in olive oil by high-temperature capillary gas chromatography

Analysis of glycerides has always been of great interest, especially to the food industry. Several methods have been developed, and attempts to improve analytical conditions are prevalent. Among these methods, high-temperature capillary gas chromatography has received particular consideration because it rapidly provides a glyceride profile. In this paper, we discuss a method to identify and quantitate mixtures of olive and soybean oils with the intention of verifying the latter as an adulterant of olive oils. The contamination of olive oil with soybean oil was detected by the presence of the triglyceride trilinolein, which does not exist in pure olive oil, although it is abundant in soybean oil. A calibration curve was constructed with several levels of contamination, and the lowest amount of detectable soybean oil was determined to be 4%.     

Production and characterization of a swiss cheese-like product from modified vegetable oils

Seven types of Swiss cheese-like products were made by recombining skim milk with various fat sources: higholeic sunflower oil (HOSO), milk fat, randomized milk fat, HOSO with commerical short-chain fatty acids (C₄−C₁₀) (SCFA) interesterified at 100 and 120% of the levels in the milk fat, HOSO with interesterified milk fat SCFA, and HOSO with dissolved free SCFA. Sensory, chemical, and physical analyses were conducted to evaluate the flavor and texture of the cheeses. All cheeses made from HOSO with interesterified SCFA were not significantly different from milk fat controls in typical Swiss flavor and volatile flavor. HOSO with interesterified SCFA scored significantly higher in these flavors than unmodified HOSO. Swiss flavor was positively correlated with sweetness (0.805), volatile flavor (0.737), caramelized flavor (0.703), non-fat solids (0.663), and SCFA (0.639), and negatively correlated with fat (−0.645) and salt (−0.482) content. A linear regression model was established for typical Swiss flavor that included fat, salt, titratable acidity, and medium- and long-chain fatty acids as variables (R ²=0.91). Instrumental texture profile analysis indicated no differences among the treatments in texture atributes except cohesiveness. The production of a good-flavored Swiss cheeselike product from HOSO with interesterified SCFA appears to be commercially feasible.     

Oil fractionation as a preliminary step in the characterization of vegetable oils by high-resolution 13C NMR spectroscopy

One hundred nine oil samples were separated chromatographically to obtain oil fractions with a decreased TAG content but with enhanced levels of the minor components that define oil genuineness and quality. The oils, which included virgin olive oils from different cultivars and regions of Europe and north Africa and refined olive, “lampante” olive, refined olive pomace, hazelnut, rapeseed, high-oleic sunflower, corn, grapeseed, soybean, and sunflower oils, were fractionated on a silica gel column with hexane/diethyl ether as the mobile phase eluent. The method was highly reproducible, and the fraction obtained contained about 15% unmodified TAG and 85% polar compounds, which included polymeric TAG, oxidized TAG, DAG, MAG, and FFA, in addition to other minor polar components of the oils. The presence of these compounds, in an enriched fraction, should provide information about the thermal, oxidative, and hydrolytic alterations of the oils, as well as many compounds of interest in determining oil genuineness. The results indicate that these fractions can provide more information than the original oils for NMR or other spectroscopic studies used in the determination of oil quality.     

Preparation and characterization of a biodegradable mulch: Paper coated with polymerized vegetable oils

Kraft paper was coated with resins based on vegetable oils and then tested for mechanical properties, rate of biodegradation in soil, and ability to inhibit weed growth. Resins included oxidatively polymerized linseed oil (LO) and a polyester formed by the reaction of epoxidized soybean oil and citric acid (ESO–CA). Tensile strength of LO-coated paper (82 MPa) was slightly higher than uncoated paper (68 MPa), while the tensile strength of ESO–CA coated paper was somewhat lower (45 MPa). Elongations to break (3–8%) were similar for all samples. The rates of weight loss and tensile strength during soil burial decreased as follows: uncoated paper > LO coated paper > ESO–CA coated paper. The polymerized oils acted as barriers to penetration of microorganisms to the cellulosic fibers. Resin-coated papers inhibited weed growth for > 10 weeks, while uncoated paper was highly degraded and ineffective by 6–9 weeks. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2159–2167, 1999     

Detection of olive oil adulteration with canola oil from triacylglycerol analysis by reversed-phase high-performance liquid chromatography

The objective of this study was to explore the use of reversed-phase high-performance liquid chromatography (RP-HPLC) as a means to detect adulteration of olive oil with less expensive canola oil. Previously this method has been shown to be useful in the detection of some other added seed oils; however, the detection of adulteration with canola oil might be more difficult due to similarities in fatty acid composition between canola oil and olive oil. Various mixtures of canola oil with olive oils were prepared, and RP-HPLC profiles were obtained. Adulteration of olive oil samples with less than 7.5% (w/w) canola oil could not be detected.     

Separation of stigmasta-3,5-diene, squalene lsomers, and wax esters from olive oils by single high-performance liquid chromatography run

To ascertain the authenticity of olive oils, the European Community Regulation requires the stigmasta-3,5-diene and wax ester contents to be determined. The official methods are time-consuming and not suitable for many daily analyses, as quality-control laboratories need. A method is presented here that allows single high-performance liquid chromatography separation of stigmasta-3,5-diene and wax esters, as well as of the squalene isomers, which give further information on the oil’s authenticity. For stigmasta-3,5-diene, the comparison with results obtained with the official method is good. Also for wax esters, the agreement was good, even if they were compared with results obtained from a quicker method as reliable as the official one. The possibility of separating the squalene isomers also at the same time makes the proposed method more advantageous. On the whole, the method, which is suggested for routine and quick screening but not for the exact evaluation of the analyte contents, seems to be a convenient choice for ascertaining on a daily basis the samples’ legal compliance (i.e., whether the analyte content is or is not below the legal value).     

A comparative study on the susceptibilities of soybean,sunflower and peanut oils to singlet molecular oxygen photooxidation

The susceptibilities of crude soybean, sunflower and peanut oils to singlet oxygen photooxidation were determined in a kinetic study. The accumulation of photosensitized hydroperoxides, determined spectroscopically, and the quenching of singlet molecular oxygen phosphorescence by the crude oils and their fatty acid methyl esters were compared. The relative tendency to photooxidation for the oils and the methyl esters was soybean ≫ sunflower > peanut. This trend was independent of the method employed in the determination of initial photodamaging. Soybean oil was demonstrated to be the most unstable product, not only due to the presence of highly unsaturated fatty acids, but also due to the absence of natural constituents, capable of providing a protective antioxidant effect. This protection was more effective in sunflower and peanut oils.     

Detection of olive oil adulteration using principal component analysis applied on total and regio FA content

Principal component analysis (PCA) has been used to establish a new method for the detection of olive oil adulteration. The data set, composed of values obtained from the determination of the mole percentage of total FA and their regiospecific distribution in positions 1 and 3 in TG of oils (pure or mixtures) by GC analysis, was subjected to PCA. 3-D scatter plots showed clearly that it is possible to distinguish the pure oils from the mixtures. Moreover it is possible to discriminate the different types of seed oil used for the adulteration.