Fatty acid monoesters of l-ascorbic and d-isoascorbic acids as antioxidants for fats and oils

Summary 1. The fatty acid monoesters of l-ascorbic and d-isoascorbic acids have been tested for antioxygenic activity in different fats and oils under various conditions and in combination with other inhibitors. 2. Traces of soap were found to have a deleterious effect on the stability of fats. This deleterious effect can be counteracted by the use of fat-soluble ascorbyl monoesters. 3. The ascorbyl monoesters used in combination with either α-tocopherol or phospholipids, or both, show a marked synergistic antioxidant effect. 4. Possible explanations are given for certain synergistic phenomena that have been observed.     

Relative nutritional value of various dietary fats and oils

The dietary and nutritional role of fats and oils is quite complex, as evident in the new biological findings about some of their components that are essential to man. Fats and oils must be considered for both their quantitative and qualitative aspects, their fatty acid compositions and relationships with average diets in different countries should be emphasized. Because of some adverse physiological effects ascribed to saturated fatty acids, a tendency to increase the intake of polyunsaturated vegetable oils has occurred to provide a good source of essential fatty acids, mainly linoleic acid. However, saturated fats still are an important part of the diet in developed countries, especially “invisible” fats. Research must continue that is related to modifications fats and oils undergo during industrial processes which affect their nutritional value. Compositions of many fats and oils are provided.     

Fats and oils as feedstocks for oleochemicals

The approximate quantity of 3 million tons estimated to be required at present for the production of oleochemicals is to be covered from a total production of more than 60 million tons of vegetable and animal fats. While the quantity of eleochemicals produced has nearly doubled in recent years, vegetable oil production alone has increased from 25 to 40 million tons in the same period. More than half the feedstocks required for oleochemicals are acid oils and other fats and oils which are unsuitable for human food. The demand for fats and oils for oleochemicals will certainly grow for price and technological reasons, but only the use of large quantities of oils and fats for diesel engines could shift this balance drastically and endanger the world supply of edible fats. A bottleneck may arise in the supply of fatty acids of medium chain length, although the use of coconut and palm kernel oil by the food industry in the highly developed countries has been on the decline. The green revolution goes on and the fat supply grows faster than the population. In addition, new approaches to plant breeding and agriculture, and biochemical processes as well, might help circumvent any conceivable shortage in the supply of oils and fats in general, and in the supply of special fatty acids in particular.     

Fettsäure-Spektren wichtiger Nahrungsfette

Fatty Acid Composition of Important Dietary Fats The recommendations issued by the German Nutrition Association (DGE) include both total fat quantities and the distribution of fatty acids in daily food intake. It is recommended that fats should account for 30% of the daily energy intake, comprising 10% each of saturated, mono-unsaturated and polyunsaturated fatty acids. An increasing number of scientific studies are quoted according to which the chain lengths of saturated fatty acids and the stereoisomers of unsaturated fatty acids play a part in raising the blood cholesterol level. Examples are given of both vegetable oils and fats and a animal and “hidden” fats. Recommendations from DGE for fat intake and fatty acid composition in fat in Germany are not reached yet. The fat intake has to be reduced.     

Seed roasting improves the oxidative stability of canola (B. napus) and mustard (B. juncea) seed oils

Animal fats and partially hydrogenated vegetable oils (PHVO) have preferentially been used for deep‐frying of food because of their relatively high oxidative stability compared to natural vegetable oils. However, animal fats and PHVO are abundant sources of saturated fatty acids and trans fatty acids, respectively, both of which are detrimental to human health. Canola (Brassica napus) is the primary oilseed crop currently grown in Australia. Canola quality Indian mustard (Brassica juncea) is also being developed for cultivation in hot and low‐rainfall areas of the country where canola does not perform well. A major impediment to using these oils for deep‐frying is their relatively high susceptibility to oxidation, and so any processing interventions that would improve the oxidative stability would increase their prospects of use in commercial deep‐frying. The oxidative stability of both B. napus and B. juncea crude oils can be improved dramatically by roasting the seeds (165 °C, 5 min) prior to oil extraction. Roasting did not alter the fatty acid composition or the tocopherol content of the oils. The enhanced oxidative stability of the oil, solvent‐extracted from roasted seeds, is probably due to 2,6‐dimethoxy‐4‐vinylphenol produced by thermal decarboxylation of the sinapic acid naturally occurring in the canola seed.     

Spurennachweis von mehrfach verzweigten Fettsäuren in Fetten

Detection of Traces of Polybranched Fatty Acids in Fats A method for the detection and quantitative determination of saturated polybranched fatty acids in animal and vegetable fats is described. The method is based on gas-chromatographic determination of polybranched fatty acid methyl esters in the methyl esters which do not form urea adducts. The following amounts of polybranched fatty acids were determined in animal fats: whale oil 15 000 ppm., fish oil 6000 ppm., butter fat 4000 ppm., beef tallow 2000 ppm. and lard 110 ppm. In different vegetable oils and fats upto 200 ppm. of polybranched fatty acids were found. Not only the difference in total content of polybranched fatty acids but also differences in their percentage composition and retention volumes in gas-chromatograms were found. This method therefore offers the possibility of identification of some of the animal fats.     

What correlation is appropriate to evaluate biodiesels and vegetable oils higher heating value (HHV)?

The heating value is one of the most important properties of animal fats, vegetable oils and biodiesels for their use as fuels in stead of petroleum.There are lots of formulae or correlations encountered in the literature to evaluate biomass fuels’ higher heating value (HHV). Lots of them are not specially established for vegetable oils, animal fats and their derivatives. In this paper, some correlations previously published and based on ultimate analysis or fatty acid composition are applied to some bio oils samples collected from the literature. The aim of this article is to investigate what of them can be used to estimate animal fats, biodiesels, vegetable oils and their derivatives HHV with a high accuracy. With an absolute average error inferior to 4%, the results show that the formulae of : Channiwala and Parikh, Boie and Vondracek, Boie, Vondracek, Fassinou et al. Milne, IGT, Demirbas and Dulong can be used at this purpose with a high accuracy by comparison to the bomb calorimetric method.     

Investigations on physical refining of animal fats and vegetable oils

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

Some Contemporary Applications of Open-Tubular Gas-Liquid Chromatography in Analyses of Methyl Esters of Longer-Chain Fatty Acids

The application of wall-coated open-tubular (capillary) gasliquid chromatographic columns to some current analytical problems in fat research is described. The liquid phase SILAR-5CP in commercially available stainless steel columns has been found to be particularly suitable for rapid screening of fats and oils for total docosenoic acid without interference from other components. Differentiation of two important 22:1 isomers (erucic acid from vegetable oils and cetoleic acid from marine oils) is possible and the erucic acid content of an oil or fat can be estimated in approximately 20 minutes. The effects of partial hydrogenation of fats on the gas-liquid chromatography of these fatty acid structural details are reviewed. The use of other liquid phases such as butanediolsuccinate polyester, and the advantages of SILAR-7CP for study of geometrical isomers in wall-coated open-tubular columns are discussed briefly, and also the potential of support-coated open-tubular columns for similar analyses of longer-chain fatty acids.     

Antioxidant activity of tocopherols,ascorbyl palmitate,and ascorbic acid and their mode of action

In the quest to use antioxidant compounds occurring in nature or related compounds, extensive studies have been made on vegetable oils, animal fats, apocarotenal, and vitamin A as substrates with ascorbyl palmitate, tocopherols, and ascorbic acid as antioxidants. Antioxidant efficiency varies with the substrate. Ascorbyl palmitate at a level of 0.01% provides a useful increase in the shelf-life of vegetable oils. Alone it is better than butylated hydroxytoluene and butylated hydroxyanisole and in combinations with other known antioxidants improves the shelf-life of all vegetable oils, as well as potato chips. Solubility problems with ascorbyl palmitate and other esters of ascorbic acid are discussed. The tocopherols have their greatest effect in protection of animal fats, carotenoids, and vitamin A. Experiments utilizing tocopherols and tocopherol combinations are presented. The activity of ascorbic acid, an excellent scavenger of oxygen, is reviewed. Quenchers of singlet oxygen do not inhibit the direct oxidation of fats and oils under the conditions used.     

Aspekte bei der Hydrierung von Fetten und Fettsäuren

Aspects of Hydrogenation of Fats and Fatty Acids Hydrogenation of fat products is of great significance, both for human and animal nutrition as well as for technical purposes. In the area of nutrition, adequate food for the increasing world population is unthinkable without utilization of all fat resources, that can be made available as food fats only after catalytic hydrogenation. In the area of technical use, a similar development is observed owing to shortage of mineral oils. Thus, fatty alcohols derived from vegetable oils and waxes can already compete in price with fully synthetic fatty alcohols derived from mineral oils. In the past 70 years of hydrogenation of fats till the present time, catalysts based on nickel have been most commonly used. In addition, small proportions of catalysts based on copper and noble metals have also been used. Homogenous catalysts have been used very recently. The present communication deals primarily with the hydrogenation of neutral fats and fatty acids using nickel catalysts. The aspects of selectivity and isomerization in the partial hydrogenation of neutral fats are discussed. In the hydrogenation of fatty acids and their derivatives, emphasis is laid on other factors, such as activity, poisoning and acid resistance of the catalyst. These factors are discussed.     

Dietary polyunsaturated fat in relation to mammary carcinogenesis in rats

High fat diets promote the development of mammary tumors induced in rats by 7,12-dimethylbenz(a)anthracene (DMBA), and polyunsaturated fats are more effective than saturated fats. This difference is related to the linoleic acid content of polyunsaturated vegetable oils, but the amount of linolealte required for maximum tumor promotion appears to be higher than indicated by earlier experiments. Comparison of the effects of a polyunsaturated vegetable oil (corn oil) containing linoleate with a fish oilo (menhaden oil) containing polyunsaturated fatty acids derived from linolenic acid showed that higher dietary mammary tumors, while corresponding levels of menhaden oil had an inhibitory effect. This is further evidence that promotion of mammary tumorigenesis by polyunsaturated vegetable oils may be mediated by prostaglandins or other biologically active eicosanoids derived from n−6 fatty acids.     

Veränderungen an Fetten bei hohen Temperaturen

Changes in Fats at High Temperatures For an uniform assessment of the continuous changes in animal as well as vegetable oils and fats by long heating at temperatures which are attained while baking and frying, the pre-requisite is, that the chemical changes are enough to be expressed analytically. The special group in the German Society for Fat Research, ?Fats as Foodstuffs”?, has taken the task of scrutinizing the methods for the chemical testing of frying fats, their applicability and reliability of the results obtained by them as evidence in the legal judgement of the foodstuffs. As examples, the provided methods — acid value, smoke point, peroxide value, epoxide value, colour, aldehyde value, oxidized fatty acids and C-polymers are tested.     

A review of methods for determining pesticide residues,contaminants and adulterants in fats and oils

Sensitive chromatographic methods are available for determining chlorinated pesticide residues and chick edema factor contaminants in fats and oils. Determination of chlorinated pesticide residues in fats and oils generally involves acetonitrile extraction, Florisil column cleanup, and analysis by electron capture gasliquid chromatography (ECGLC). However, other procedures are available including dimethyl sulfoxide extraction and sweep codistillation. Sensitive screening tests for chick edema factor involve alumina column fractionation of isolated unsaponifiable matter, sulfuric acid cleanup, and examination by ECGLC. Admixtures of animal and vegetable fats are detected by the gasliquid chromatography (GLC) of isolated sterols, and individual vegetable oils can be characterized by GLC analysis of the sterols as well as of the other unsaponiflable constituents. Presented at the AOCS Short Course, “Processing Quality Control of Fats and Oils,” East Lansing, Mich., Aug. 29–Sept. 1, 1966.     

A review of rapeseed oil uses for edible purposes

Food technological aspects on the use of rape-seed oil and otherCruciferae seed oils as salad oils, in margarine, shortenings and some other foods are briefly reviewed. It is concluded that these oils in hydrogenated or nonhydrogenated form may compete favorably with other vegetable oils and animal fats. One of nine papers published from the Symposium, “Cruciferous Oilseeds,” ISF-AOCS World Congress, Chicago, September 1970.     

Antioxidant activity and stability of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid

6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid in thin layer tests in vegetable oils and animal fats has two-four times the antioxidant activity of butylated hydroxytoluene and butylated hydroxyanisole and is more active than propyl gallate, nordihydroquaiaretic acid, ascorbyl palmitate, and α- and γ-tocopherols. It is also more active than tertiary butylhydroquinone in chicken and pork fats and corn, peanut, sunflower, and safflower oils in thin layer tests. Tertiary butylhydroquinone is slightly more active in corn, soybean, cottonseed, and peanut oils in the active oxygen method, probably due to decomposition of the chroman at 98 C. This decomposition is inhibited by ascorbic acid. The chroman is synergized by ascorbyl palmitate-thiodipropionate and ascorbic acids. Active oxygen method values of 190 hr are obtained in combination with the latter. A spectrofluorometric assay for 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid has been developed. The compound is 95–100% stable for 2 months at room temperature and 45 C, and a low level of toxicity is found. The copper and iron breakdown products of the chroman have been determined. A possible relationship between these products, protection of the chroman by ascorbic acid and ethylene diaminetetraacetic acid, and a mechanism of action is presented.     

生物柴油的制备技术研究进展

生物柴油作为一种可再生的绿色环保燃料,主要是由动植物油脂经过酯交换反应生成。文章概述了国内外制备生物柴油方法,重点介绍了酸、碱、酶催化及超临界工艺方法的研究进展,并对我国生物柴油产业化发展前景进行了展望。     

Techno-economic analysis of a biodiesel production process from vegetable oils

Biodiesel, which is defined as the monoalkyl esters of long chain fatty acids derived from a renewable lipid feedstock, has received considerable attention worldwide as a medium-term alternative to diesel fuel obtained from petroleum. Biodiesel can be produced by the transesterification of vegetable oils or animal fats using short-chain alcohols in the presence of a suitable catalyst and glycerol is the only byproduct obtained in significant quantities. In this work a techno-economic analysis of a process that produces biodiesel from vegetable oils is presented with the aim to investigate the dependence of the critical profitability indicators on the production capacity.     

Biodiesel processing and production

Biodiesel is an alternative diesel fuel that is produced from vegetable oils and animal fats. It consists of the monoalkyl esters formed by a catalyzed reaction of the triglycerides in the oil or fat with a simple monohydric alcohol. The reaction conditions generally involve a trade-off between reaction time and temperature as reaction completeness is the most critical fuel quality parameter. Much of the process complexity originates from contaminants in the feedstock, such as water and free fatty acids, or impurities in the final product, such as methanol, free glycerol, and soap. Processes have been developed to produce biodiesel from high free fatty acid feedstocks, such as recycled restaurant grease, animal fats, and soapstock.     

Fate of dietary sterols in hydrogenated oils and fats

Samples of table margarines, so-called polyunsaturated table margarines, hydrogenated vegetable oils, and so-called polyunsaturated hydrogenated vegetable oils were shown by infrared spectroscopy to contain hydrogenated components. Examination of the sterols from these oils by argentation thin layer chromatography and gas liquid chromatography did not reveal campestanol, stigmastanol, or Δ²²-stigmastenol, the expected hydrogenation products of the natural sterols. The sterol compositions of the above samples, animal fats, and blends of hydrogenated vegetable oils and animal fats were determined. The compound 24-methyl cholest-7-en-3β-ol was identified tentatively in sunflower and safflower oils.