Detection of adulteration

A program of work is in progress to establish the levels and ranges of fatty acids and other components present in the major edible vegetable oils. Authentic samples from the major producing areas for such oil have been obtained and analyzed. In the case of palm oil, ranges of the fatty acid composition and of the acids at the triglyceride 2-position, have been obtained for about 40 samples. These data were used to calculate enrichment factors, and triglyceride carbon number compositions, using a small computer program. Comparison with experimentally determined carbon number compositions were then made. Good correlations were found for whole unadulterated oils, but not for oil fractions. Unfortunately, these differences were insufficient to detect contamination of palm oil by 10 or 20% levels of other oils, or of palm fractions. Compositional ranges of sterols and tocopherols have also been determined on a selection from the original set of palm samples. Work on sunflower seed and groundnut oils has followed the same lines, particular attention having been paid to linolenic acid and, in the case of groundnut oil, also erucic acid, levels. Some groundnut kernels were found to have an oil with a component which cochromatographed with methyl erucate during fatty acid determination. This unknown constituent was studied by gas chromatography-mass spectrometry, and is thought to comprise a mixture of epoxy fatty acids. Analysis of the triglyceride fraction isolated from groundnut oil by thin layer chromatography removes this unknown constituent, and simplifies interpretation of the fatty acid composition of groundnut oil.     

Composition of oil

International trade in palm oil has increased considerably over the last ten years, and so too has the trade in processed palm oil products, especially palm fractions. It is important to establish reliable purity criteria for palm oil, not only because of the commercial need to verify oil authenticity, but also to comply with foodstuff labelling legislation in many countries. Palm kernel and coconut oils both contain about 47% lauric acid. This gives the oils close similarities in physical and chemical properties. The oils do differ, however, and it is important to be able to distinguish between them. Purity problems can arise as a result of commingling of oils with one another, or as a result of fractionation perhaps coupled with subsequent blending. A research program jointly funded by the (U.K.) Ministry of Agriculture, Fisheries and Foods, the Federation of Oils, Fats & Seeds Associations Ltd (FOSFA International), and the Leatherhead Food RA, was established to study purity characteristics of the major edible vegetable oils. Forty-seven samples of crude palm oil were obtained from reliable sources, often plantation managers, together with five samples of palm olein and eight samples of palm stearin. Fifty-four palm kernel and 23 coconut oils were obtained in the laboratory from seed samples of known geographical origins and authenticities. These oil samples were analyzed for fatty acid, triglyceride, sterol and tocopherol compositions; the melting properties were also determined, and in the case of palm oil the compositions of the acids at the triglyceride 2-positions were measured. Compositional ranges will be presented for the different geographical production areas in each case and related to existing data, e.g., of PORIM and Codex. An initial statistical analysis of the results has shown that a combination of values from the carbon number analysis differentiates palm kernel and coconut oils, and can be used to decide on the proportion of each in a blend. In the case of palm oil samples suspected to be contaminated with palm fractions, it was found useful to plot melting point against iodine value, and to compute the product of the C48 triglyceride content and the palmitic acid enrichment factor.     

Purity assessments of major vegetable oils based on δ13C values of individual fatty acids

The fatty acid compositions and δ¹³C values of the major fatty acids of more than 150 vegetable oils were determined to provide a database of isotopic information for use in the authentication of commercial maize oil. After extraction of oils from seeds, nuts or kernels, and methylation, fatty acid compositions were determined by capillary gas chromatography. All compositions were within the ranges specified by the Codex Alimentarius. Gas chromatography combustion-isotope ratio mass spectrometry was employed to determine the δ¹³C values of the major fatty acids of the oils. A large number of pure maize oils and potential adulterant oils from various parts of the world were studied to assess the sources of variability in δ¹³C values. Such information is vital to establishing the compound specific isotope technique as a reliable means of assessing vegetable oil purity. Variability in δ¹³C values was related to the geographical origin of the oil, year of harvest, and the particular variety of oil. This suggests that the ultimate δ¹³C values of fatty acids are determined by a combination of environmental and genetic factors.     

木本油料脂肪酸组成、提纯及其应用研究进展

木本油料是我国传统工业油料,应用领域广泛,可作为优质的食用植物油的来源,也可作为生产生物柴油的原料,并且还被用于饲料添加剂和化妆品行业。木本油料中C12~C18不饱和脂肪酸含量高,易被人体吸收,不同提取技术(压榨法、水酶法、超声波辅助法、浸出法等)对木本油料的脂肪酸组成及含量的影响较小。本文对橡胶籽油、核桃油、椰子油、山苍子核仁油、牡丹籽油、油茶籽油和棕榈油等7种木本油料的资源量、应用情况做了简单介绍,并综述了7种木本油料的脂肪酸组成及其提取纯化技术,重点介绍了木本油料中的中长碳链不饱和脂肪酸的提纯技术,并对提纯后的月桂酸、油酸、亚油酸、亚麻酸的应用进行了综述和展望。     

Chemical evaluation of egyptian citrus seeds as potential sources of vegetable oils

Seeds of the citrus fruits orange, mandarin, lime and grapefruit were analyzed. Petroleum ether-extracted oils of such seeds amounted to more than 40% of each. Physical and chemical properties of the extracted oils are presented. Samples of the extracted oils were saponified and the unsaponifiables and fatty acid fractions isolated. The isolated unsaponifiables and fatty acids were analyzed by GLC. GLC analysis of the unsaponifiables revealed compositional patterns differ-ent in number, type and relative concentration of fractions according to type of citrus seed oil, depending on the solvent system used for oil extraction and unsaponifiable matter isolation. The compositional patterns of the unsaponifiables were similar to that of cottonseed oil. Mandarin and grapefruit oils are free of cholesterol. The data demonstrate that the fatty acid compositional patterns of the oils differ; Mandarin seed oil contains the largest number of fatty acids, and grapefruit seed oil contains the lowest. The total amounts of volatile fatty acids in these oils are generally higher than those of other edible oils. Lime seed oil is similar, in the degree of unsaturation, to soybean oil. The orange oil pattern is similar to cottonseed oil. The amount of total essential fatty acids in lime seed oil is the highest of the oils studied.     

滇产植物油理化指标测定

研究滇产食用植物油的理化特征与储藏期品质变化规律。以两种特色植物油为对照,对云南出产的五种植物油脂的理化指标进行评价和对比。同时使用过氧化值和酸价,对所研究的油脂的储藏期品质变化进行初步探索。结果表明:云南产植物油质量均满足国标要求。但由于其加工工艺原因,植物油级别较低。含有不饱和脂肪酸的植物油在光照情况下过氧化值和酸价明显改变,可作为质量变化的主要指标。云南出产的四种特色植物油脂不饱和脂肪酸含量较高,是良好的食用油产品;但仍需改善加工工艺以提高其级别。葡萄籽油、红花籽油需添加额外抗氧化剂稳定其品质;过氧化值是最适于进行日常油品质量控制的指标。     

A conversion factor to determine phospholipid content in soybean and sunflower crude oils

The major phospholipids (PL) from soybeans and sunflowers were separated by 2-dimensional thin layer chromatography (TLC) and the fatty acid composition of each PL was determined by gas liquid chromatography (GLC). PL from soybeans and sunflowers contained high percentages of linoleic and palmitic acids. Only phosphatidylinositol (PI) from both oilseeds were similar in fatty acid composition and the principal acid was palmitic acid. Sunflower phospholipids, except for PI, contained twice as much oleic acid as did those from soybeans. Sunflower PI contained very low but measurable quantities of heptadecanoic acid. The molecular weights (MW) of individual PL were based on their fatty acid composition. The MW found for soybeans and sunflower PL were quite similar even though their fatty acid compositions were different. The average MW of PL in crude soybean and sunflower oils was determined based on the MW of individual PL and their composition in the PL fraction. From that MW, a factor for converting phosphorous content in oil to its PL content was calculated. For both oils, the factor was 25.     

Preparation and analysis of some food fats and oils for fatty acid content by gas-liquid chromatography

The fatty acid compositions of some food fats and oils were determined by gas-liquid chromatography (GLC) before and after application of reagents and conditions of some extraction procedures. The extraction procedures studied had a nonsignificant effect on the fatty acid compositions. Procedures leading to methyl ester formation through a series of room temp reactions were selected over procedures requiring higher temp reactions, on the basis of yield of products, fatty acid compositions of food lipids of simple composition, or both. These procedures were then used to prepare some food fats and oils for analysis by GLC and the fatty acid compositions determined in this manner are presented. Food Composition Laboratory, ARS, USDA.     

Studies in interesterification. II. Acidolysis of some vegetable oils with lauric acid

Acidolysis reactions of cottonseed oil, peanut oil, mahua oil (Madhuca latifolia), and palm oil with lauric acid were investigated with special reference to the influence of catalysts and the relative proportions of oil and lauric acid on the extent and type of fatty acids displaced from an oil. Catalysts such as sulfuric acid, zinc oxide, calcium oxide, magnesium oxide, aluminum oxide, and mercuric sulfate were used. The reaction generally was carried out by heating oil and lauric acid at 150C±2 for 3 hr. The reaction products were separated and then analyzed by UV spectrophotometry and GLC. Sulfuric acid was found to be the best catalyst with 1 part of oil and 1.2 parts of the displacing acid (lauric acid) for displacement of high-molecular-weight fatty acids from an oil by low-molecular-weight fatty acids. The nature of the displacement of fatty acids varied from oil to oil, depending on their compositions. It was further indicated that linoleic acid was displaced preferentially over oleic acid in an amount dependent on its initial content in an oil with a corresponding increase in saturated acids content. A broad similarity in displacement patterns, in general, was noted; the fatty acids above C₁₈ were not displaced as in the case of peanut oil. The results demonstrate the feasibility of introducing lauric acid in the vegetable oils for the production of interesting oils with vastly different physical and chemical properties.     

Vegetable oil raw materials

Vegetable oils that are important to the chemical industry include both edible and industrial oils, which contribute 24% and 13.5%, respectively, compared to 55% for tallow, to the preparation of surfactants, coatings, plasticizers, and other products based on fats and oils. Not only the oils themselves but also the fatty acids recovered from soapstock represent a several billion pound resource. Coconut oil is imported to the extent of 700-1,000 million pounds per year. Its uses are divided about equally between edible and industrial applications. Safflower oil has a relatively small production, but 15–25% of the oil goes into industrial products. Soybean oil, the major edible oil of the world, is produced in the United States at the rate of 11,000 million pounds per year with more than 500 million pounds going into industrial uses, representing 5% of the total production. Castor oil is imported to the extent of about 100 million pounds per year. Linseed oil production has declined drastically over the last 25 years but still amounts to about 100 million pounds per year. Oiticica and tung oils are imported in lesser amounts than castor and linseed oils. New crops that have industrial potential, as well as the traditional vegetable oil crops, include seed oils from crambe,Limnanthes, Lesquerella, Dimorphotheca, Vernonia, andCuphea plants. Crambe oil contains up to 65% erucic acid. Oil fromLimnanthes contains more than 95% of fatty acids above C₁₈.Lesquerella oil contains hydroxy unsaturated acids resembling ricinoleic acid from castor oil.Dimorphotheca oil contains a conjugated dienol system.Vernonia oils contain as much as 80% epoxy acids. TheCuphea oils contain a number of short chain fatty acids. Of these, crambe,Limnanthes, andVernonia are probably the most developed agronomically. Competition between vegetable oils and petrochemicals for the traditional fats and oil markets has been marked over the past 25 years, but prices for petrochemicals have accelerated at a greater rate than those for vegetable oils; and, it is now appropriate to reexamine the old as well as the new markets for fatty acids.     

Enzymatic synthesis of capric acid-rich structured lipids (MUM type) using Candida antarctica lipase

The objective of the work was to produce capric acid rich structured lipids starting from various Indian indigenous vegetable oils, such as rice bran, ground nut and mustard oils. Acidolysis reaction between individual vegetable oils and capric acid in one is to three molar ratios at 45 degree centigrade temperature was carried out using position specific Candida antarctica lipase so as to protect the Sn-2 position of the oils which are rich in unsaturated fatty acids. The incorporation of capric acid depended on the reaction time showing 6 % within 6 h and 30.8 % in 72 h with rice bran oil. Similarly, in ground nut oil incorporation of capric acid was 34.2 % in 72 h compared to 5.3 % in 6 h. Thus mustard oil showed much lower incorporation than the other two oils, with 3.3 % and 19.5 % in 6 and 72 h respectively. The incorporation of capric acid was influenced by the nature of the fatty acids present in the original oil. The fatty acid composition of Sn-2 position of the structured triacylglycerols of the three oils revealed that capric acid was mainly replacing the fatty acids occupying the Sn-1 and 3 positions of the triglyceride molecule.     

Insights into the compatibility of vegetable-based plasticizers on the performance of filled rubber vulcanizates

Substitution of petroleum-based processing oils with eco-friendly sustainable plasticizers in rubber compounds has gained much global attention due to their toxicity. In this regard, so far, the major attempts have focused on substituting aromatic oils with fatty acid based vegetable oils. In this work, the chemical and physical effects of canola oil as a model of fatty acid based vegetable oils on the process-ability, vulcanization kinetics, and final properties of carbon-black filled styrene–butadiene rubbers are systematically investigated. In contrast to the previous studies, it was shown that although these types of vegetable oils have a plasticizing impact, they can indeed threaten the requirements of reinforcing criteria in rubber vulcanizates. The final properties of the vulcanizates were found to be deteriorated due to the incompatibility of canola oil fatty acids constituents with rubber matrix and especially as a result of chemical interference of their unsaturated bonds in sulfur vulcanization kinetics.     

Extraction of omega‐6 fatty acids from speciality seeds

‘Omega‐6 vegetable oils’ are a small but important group of vegetable oils used widely in the food, neutraceutical, cosmetic and pharmaceutical industries for their linoleic acid (18:2 n‐6) and more importantly gamma linolenic acid (18:3 n‐6) content. These omega‐6 fatty acids have numerous health benefits recognized worldwide. With linoleic acid being readily available from many dietary sources, one wonders why there is a need to extract the oil from speciality oilseeds, however those that suffer with many of the conditions that omega‐6 fatty acids are said to be beneficial for are frequently advised to take extra supplements of these fatty acids. Due to their wide use as a nutraceutical, omega‐6 fatty acids are in high demand, causing a niche market for extraction of these oils from speciality seeds.     

Low linolenic soybeans and beyond

Low linolenic soybean oil is the first in a series of modified oilseed products to be introduced to meet food company and consumer needs. Consumer packaged goods and foodservice companies are currently using this oil to successfully replace partially hydrogenated soybean oil, resulting in the reduction of trans fatty acids from the food supply. In addition to meeting consumer demand for healthier foods, many food processors have chosen low linolenic soybean oil based on taste, performance and cost benefits. Seed companies continue to utilize traditional breeding, marker assisted breeding and biotechnology approaches to modify oilseeds that produce oils with health and nutrition benefits. Additional modified oilseeds are at various stages of development. Soybeans with increased levels of stearic acid are being developed as an alternative to partially hydrogenated fats and high saturate fats required to provide solids and structure to food. High stability fry oils with increased levels of oleic acid, reduced levels of linolenic acid as well as a version with lower saturated fat are being developed. Soybeans are also being modified to offer more sustainable sources of omega‐3s including stearidonic acid and eicosapentaenoic acid/docosahexaenoic acid which will result in more efficacious sources of omega‐3s compared to alpha‐linolenic acid‐containing vegetable oil and improved functionality/stability compared to fish and algal oils.     

Physical refining

By reviewing current commercial physical refining processes a prospectus is suggested for the future objectives in this field of edible oil processing. The paper reviews widely used physical refining processes for the relatively high free fatty acid (FFA) laurics and palm oil and a commercial operation for physical refining of maize and sunflower oils. In addition, the relatively new departure of physical refining of soybean oil is discussed using data from recent development work. This system is used to demonstrate present trends in the development sector of the industry. Reference to similar work on pretreatment of rapeseed oil is included. The discussion is used to suggest guidelines for design of a flexible physical refining system for application to major oils processed by European refiners. There is still no physical refining process that can handle successfully on a commercial scale all qualities of soybean oil. We must envisage a system of physical refining that is able to deal with the most difficult soybean oil and thus assume it will handle all the less difficult oils.     

Linolenic Acid as the Main Source of Acrolein Formed During Heating of Vegetable Oils

Acrolein, which is an irritating and off-flavor compound formed during heating of vegetable oils, was estimated by the gas–liquid chromatography (GLC). Several vegetable oils such as high-oleic sunflower, perilla, rapeseed, rice bran, and soybean oils were heated at 180 °C for 480 min and then the concentration of acrolein in the head space gas was determined by GLC. The formation of acrolein was greatest in perilla oil among the tested oils, while it was much lower in rice bran oil and high-oleic sunflower oil. There was a good correlation between the level of acrolein and linolenate (18:3n-3) in the vegetable oils. To investigate the formation of acrolein from linolenate, methyl oleate, methyl linoleate, and methyl linolenate were also heated at 180 °C, and the amounts of acrolein formed from them were determined by GLC. The level of acrolein was the greatest in methyl linolenate. Acrolein was also formed from methyl linoleate, but not from methyl oleate. Acrolein in vegetable oils may be formed from polyunsaturated fatty acids, especially linolenic acid but not from glycerol backbone in triacylglycerols.     

Current advances in sunflower oil and its applications

The fatty acid and triacylglycerol composition of a vegetable oil determine its physical, chemical and nutritional properties. The applications of a specific oil depend mainly on its fatty acid composition and the way in which fatty acids are arranged in the glycerol backbone. Minor components, e. g. tocopherols, also modify oil properties such as thermo‐oxidative resistance. Sunflower seed commodity oils predominantly contain linoleic and oleic fatty acids with lower content of palmitic and stearic acids. High‐oleic sunflower oil, which can be considered as a commodity oil, has oleic acid up to around 90%. Additionally, new sunflower varieties with different fatty acids and tocopherols compositions have been selected. Due to these modifications sunflower oils possess new properties and are better adapted for direct home consumption, for the food industry, and for non‐food applications such as biolubricants and biodiesel production.     

Effects of unsaturation and different ring-opening methods on the properties of vegetable oil-based polyurethane coatings

A variety of vegetable oil-based, waterborne polyurethane dispersions have been successfully synthesized from different vegetable oil polyols exhibiting almost constant hydroxyl functionalities of 2.7 OH groups per molecule. The vegetable oil polyols, which have been prepared from vegetable oils with different fatty acid compositions (peanut, corn, soybean, and linseed oil), range in residual degree of unsaturation from 0.4 to 3.5 carbon–carbon double bonds per triglyceride molecule. The effects of residual unsaturation on the thermal and mechanical properties of the resulting polyurethane films have been investigated by dynamic mechanical analysis, differential scanning calorimetry, and thermal gravimetric analysis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has been used to accurately determine the molecular weight and mass distribution of the vegetable oil polyols. Higher residual unsaturation results in polyurethane films with increased break strength, Young's modulus, and toughness. This work has isolated the effect of unsaturation on vegetable oil-based polyurethane films, which has been neglected in previous studies. The effect of different oxirane ring opening methods (methanol, butanol, acetic acid, and hydrochloric acid) on the properties of the coatings has also been examined.     

Precision of low trans fatty acid level determination in refined oils. Results of a collaborative capillary gas-liquid chromatography study

The results of a collaborative study by 38 laboratories were analyzed statistically to calculate the precision of a novel capillary gas-liquid chromatography (GLC) method for the determination of low levels of trans fatty acids (TFA) in edible oils. The participants came from 17 countries, mainly European, and were spread evenly between Unilever companies and external laboratories. All participants used the same GLC method, including a temperature optimization step, which is suitable for the determination of a large range of TFA levels in refined oils and fats and for the determination of total saturated fatty acid, cis mono- and cis-cis methylene-interrupted polyunsaturated fatty acid isomers. For TFA levels down to 0.5%, the collaborative study yielded values for R_within that ranged from 0.08 to 0.13% (absolute values) and for R_between from 0.2 to 0.4%, depending on the isomer distribution in a particular edible oil. The proposed GLC method allows reliable TFA analysis at low levels that is suitable for monitoring oil processing practices and intake control.     

The development and application of novel vegetable oils tailor‐made for specific human dietary needs

Conventional edible oils, such as sunflower, safflower, soya bean, rapeseed (canola) oils, were modified to obtain high‐oleic, low‐linoleic or even low‐linolenic oils. The aim was to develop salad, cooking and frying oils, that are very stable against lipid peroxidation. They are also suitable for margarine blends, as additives to cheeses and sausages, or even as feed components. Oils containing higher amounts of medium‐chain length or long‐chain polyunsaturated fish oil fatty acids are suitable as special dietetic oils or as nutraceuticals. High‐stearic oils are designed as trans‐fatty acid‐free substitutes for hydrogenated oils. New tailor‐made (designer) oils are thus a new series of vegetable oils suitable for edible purposes, where conventional oils are not suitable.