Separation of saturated/unsaturated fatty acids

Fatty acid mixtures can be separated into one fraction rich in saturated fatty acids and the other rich in unsaturated acids. Since saturated fatty acids have a higher melting point than unsaturated, liquid mixture to be fractionated is cooled to a temperature at which the larger part of the saturated acids crystallize, while the greater part of unsaturated acids remain in liquid form. Different industrial methods to separate the two phases are described. The oldest and simplest method is slowly to cool and crystallize the mixture in shallow pans to form cakes which then are pressed in presses of different design. By applying high pressure, the liquid olein is thus squeezed out from the cake, leaving the stearin fraction behind. A new process to separate the phases is to mix an aqueous solution, containing a wetting agent, with the crystallized fatty acid mixture. The stearin crystals are thus wetted and transferred into the aqueous phase, which then can be separated from the olein phase in a centrifuge. The stearin/aqueous suspension is heated to melt the stearin, which can then be separated in a second centrifuge. Other methods to improve phase separation use organic solvents, among which are methanol, acetone, methyl formate and propane. In the solvent fraction process, the miscella has to be cooled to a lower temperature than in the aforementioned methods, due to the solubility effect of the solvents. The solvents are removed by distillation from the fraction. Typical operation results with different types of raw materials are given. The advantages and disadvantages of the different methods are discussed.     

The saturated fatty acids of Japan wax

Summary Myristic and behenic acids, hitherto not reported therein, have been shown to be components of the glycerides of Japan “wax” in contrast to the nonexistence of an alleged heneicosanoic acid. Esterfractionation analysis revealed the following composition: myristic acid 1.9 per cent, palmitic acid 67.5 per cent, stearic acid 11.6 per cent, arachidic acid 0.04 per cent, behenic acid 0.01 per cent, unsaturated acids 13.6 per cent, and dicarboxylic acids 5.3 per cent. A preliminary investigation of the latter resulted in the isolation of an acid which by virtue of its melting point and molecular weight has been tentatively characterized as heneicosane dicarboxylic acid (C₂₃). However, final proof of identity must rest upon subsequent synthesis of this acid. This investigation is being supported by a grant from the Wisconsin Alumni Research Foundation whose aid is gratefully acknowledged.     

Viscosities of fatty acids and methylated fatty acids saturated with supercritical carbon dioxide

The viscosities of several types of lipids saturated with supercritical carbon dioxide (SC-CO₂) were measured with a high-pressure capillary viscometer. Oleic acid and linoleic acid were evaluated from 85 to 350 bar at 40 and 60°C. The more SC-CO₂-soluble methylated derivatives of these fatty acids were evaluated from 90 to 170 bar at 40 and 60°C. The complex mixture of anhydrous milk fat (AMF) was evaluated from 100–310 bar at 40°C. The viscosities of the methylated fatty acids saturated with SC-CO₂ decreased between 5 and 10 times when the pressure increased from 1 to 80 bar, followed by a further decrease by a factor of 2 to 3 when the pressure was increased from 80 to 180 bar. The viscosities of the fatty acids and AMF saturated with SC-CO₂ had viscosity reduction similar to the methylated fatty acids between 1 and 80 bar, but they decreased much less between 80 and 350 bar. At constant pressure, the viscosity of the fatty acids and AMF decreased with increasing temperature, whereas the viscosity of the methylated fatty acids increased with increasing temperature. The lipid/SC-CO₂ mixtures were Newtonian, and their viscosities were best interpreted by using the mass concentration of dissolved SC-CO₂ in the lipids and the pure component viscosities.     

Maleyl esters of monoglycerides of saturated fatty acids

Esterification between maleic anhydride and monoglycerides of saturated fatty acid has been studied. The nature of reaction vessels, temperature and reaction time have been evaluated in view of the product distribution in the final product. Concentration of monoesters (half-esters) diesters and dimers has been calculated and related to the reactants’ ratio, time and temperature of the esterification.     

On the syntheses of branched saturated fatty acids

In order to investigate the relation between the structure of mono-branched saturated fatty acids and their physical properties, a three-factor central composite design was constructed. For this purpose sixteen different fatty acids were prepared. The synthetic strategy was to use if possible, a few common starting materials for the preparation of most of the acids. Thus alkylation and hydrolysis of oxazolines were used for the preparation of 2-butylhexanoic acid, 2-methyloctadecanoic acid, 2-hexadecyloctadecanoic acid and 2-pentyloctadecanoic acid. A number of acids were prepared from thiophene derivatives followed by desulfurization with Raney-Nickel alloy under alkaline conditions. Thus, starting from 3-ethylthiophene, 4-ethyl-2-thiophenecarboxylic acid and 4-ethyl-2-methyl-5-thiophenecarboxylic acid were prepared, which upon desulfurization gave the desired 4-methylhexanoic acid. From 3-bromo-2-methylthiophene, 3-ethyl-2-methyl-5-thiophenecarboxylic acid was preparedvia 3-acetyl-2-methylthiophene and 3-ethyl-2-methylthiophene. Desulfurization gave 4-ethylhexanoic acid. Another approach started with 2-acylthiophenes, which were reacted with Grignard reagent to yield the appropriate olefins. By metalation and reaction with carbon dioxide, these were transformed to the corresponding 2-thiophenecarboxylic acids. Upon desulfurization, the desired fatty acids were obtained. In this way 6-propyldecanoic acid, 6-hexyldodecanoic acid, 6-methyldodecanoic acid and 6-pentylpentadecanoic acid were prepared. The remaining four acids were prepared from some of the branched acids described above through Kolbe reactions of dioic acids. Thus 16-methyloctadecanoic acid and 10-methyl-dodecanoic acid were obtained from 4-methylhexanoic acid, 16-ethyloctadecanoic acid from 4-ethylhexanoic acid and 9-pentyloctadecanoic acid from 6-pentylpentadecanoic acid.     

Crystal structures of binary systems of saturated fatty acids

Data on crystal lattices of 13 different mixtures of the system palmitic acid:stearic acid (C₁₆/C₁₈) could be obtained by means of X-ray and electron diffraction. The modification occurring in all concentrations was found to be in conformity with the known γ₄- or C-form of the pure components. It is characterized by the fact that, in mixtures with 95-60 mol % stearic acid, the shorter chained palmitic acid molecules may be incorporated in the crystal lattice of pure stearic acid without dimension c of the unit cell being changed. In concentration ranges of 50–20% C₁₈-molecules, one form of mixture which proves to be stable is characterized by constancy of nearly all unit cell parameters of various mixture ratios. From SP10 to SP0, the lattice constants of pure palmitic acid are mainly obtained. The occurrence of C₁₈-molecules of up to 10% in the unit cell of palmitic acid results in a slight decrease of the angle β by 1–2^o and an enlargement of the distance to neighbored molecules.     

Effects of dietary saturated andTrans fatty acids on tissue lipid composition and serum LCAT activity in the rat

Groups of rats were fed from weaning with diets containing 5% by wt of hydrogenated coconut oil (HCO), safflower oil, or a concentrate of ethyl elaidate and linolelaidate (TRANS) as the sole source of dietary fat. Fatty acid composition of the lipid classes from serum, liver, heart, and kidney was determined, and the serum lecithin: cholesterol acyl transferase (LCAT) activities were assayed for each animal. Serum LCAT activity was increased by both the HCO and TRANS diets in the early stages of the development of an essential fatty acid (EFA) deficiency but was suppressed in the animals of the TRANS group as they became older. The HCO and TRANS groups exhibited changes in tissue lipid fatty acid composition, as well as reduced growth, characteristic of an EFA deficiency. Conversion of oleic acid to eicosatrienoic acid was impaired in the animals fed the TRANS diet, greatly increasing the octadecenoic acid content of the tissue lipids at the expense of eicosatrienoic acid. The TRANS diet also suppressed incorporation of eicosatrienoic acid into cholesteryl esters of tissue and serum, indicating that, when fed as the sole source of unsaturated fat,trans fatty acids influenced the metabolism of unsaturated fatty acids and cholesterol.     

Synthesis of estolides from oleic and saturated fatty acids

Oleic acid and various saturated fatty acids, butyric through stearic, were treated with 0.4 equivalents of perchloric acid at either 45 or 55°C to produce complex estolides. Yields varied between 45 and 65% after Kugelrohr distillation. The estolide number (EN), i.e., the average number of fatty acid units added to a base fatty acid, varied as a function of temperature and saturated fatty acid. The shorter-chain saturated fatty acids, i.e., butyric and hexanoic, provided material with higher degrees of oligomerization (EN=3.31) than stearic acid (EN=1.36). The individual, saturated fatty acid estolides each have very different characteristics, such as color and type of by-products. The higher-temperature reactions occurred at faster rates at the expense of yield, and lactones were the predominant side products. At 55°C, lactone yields increased, but the δ-γ-lactone ratio decreased; this led to lower estolide yields. The opposite trend was observed for the 45°C reaction. The saturate-capped, oleic estolides were then esterified with 2-ethylhexyl alcohol, and the chemical composition of these new estolides remained consistent throughout the course of the reaction.     

Desaturation of saturated fatty acids by rat liver microsomes

A method was developed for the rapid determination of the initial velocity of the desaturation of saturated fatty acids. In the reaction, DPNH was a more efficient electron donor than TPNH. Fatdeficient rats have a 2.5-fold greater level of acyl desaturase per milligram of liver microsomal protein than did animals fed lab chow. Increasing the chain length of the acyl substrate from 10∶0 to 18∶0 increases the rate of monoene formation, but 19∶0 is desaturated at a rate lower than that for 15∶0. The energy of activation (Ea) for the overall desaturation reaction has been determined for 12∶0 through 19∶0. The Ea values for desaturation of 13∶0 and 16∶0 are markedly lowr than for the other acids. An interaction between the alkyl chain of the substrate and polyunsaturated acids of the microsomal membrane-bound phospholipids is postulated to explain the recurring 3-carbon pattern of the relative reaction rates of the various acyl substrates.     

Thioesterification of platelet proteins with saturated and polyunsaturated fatty acids

We have demonstrated that more than 20 platelet proteins can be acylated with fatty acids via thioester linkages. These include the glycoprotein IX beta chain of glycoprotein Ib, components of the von Willebrand factor receptor on the platelet surface, P-selectin, and α subunits of G_z, G_q, and G_i. Our studies have shown that platelet proteins can be posttranslationally acylated in thioester linkages not only with palmitate but with myristate and also with the eicosanoid precursor fatty acids arachidonate and eicosapentaenoate. Thioesterification of platelet proteins with fatty acids other than palmitate may have significant functional consequences for reversible binding of proteins to membranes.     

On the syntheses of triacylglycerols from branched saturated fatty acids

A number of triacylglycerols with branched acyl groups were prepared via 1,2-isopropylidene glycerol for the purpose of studying three different physical properties: gel point, refractive index, and density. The monoacid triacylglycerols were prepared either via the corresponding acids or the acyl chlorides.     

Effect of diet on fatty acids in the lipoprotein cholesteryl esters of type IIa and normal individuals

Four normal and two individuals with type IIa hyperlipoproteinemia were placed on the National Heart and Lung Institute Type IIa Diet (less than 300 mg of cholesterol per day, high polyunsaturated, low saturated fat diet) for 1 week and on a normal diet the following week. Plasma samples were obtained and the cholesterol contents of plasma and of very low density, low density and high density lipoproteins determined. The cholesteryl esters in one type IIa and two normal individuals were identified. The cholesteryl esters in type IIa very low density lipoproteins from blood drawn 45 min after the last meal in each dietary period, contained less 18:2 than from the normal. After the first dietary period, the very low density lipoprotein cholesteryl ester 18:2 content for the type IIa was 37.2M% and for the normals, 54.7M%. After the second dietary period, the corresponding values were 49.7M% and 56.7M%. Fasting samples had lower 18:2 contents in the low density lipoproteins from the Type IIa subject following both dietary periods and in the high density lipoproteins following the Type II diet.     

Potential of animal nutrition to decrease the saturated fatty acids in meat and milk

Medical authorities recommend that energy intake from saturated fatty acids (SFA) should not exceed 10% of total energy intake. Milk and meat, because of their relatively high SFA concentration and level of consumption, make a large contribution to human SFA consumption. Strategies to decrease the SFA content in meat and milk include inclusion of forage in the ration of ruminants and supplementation of dietary intake of ruminants and monogastrics with unsaturated fatty acid‐rich oilseeds, fish oil or marine algae. The influences of these manipulations will be illustrated and the likely future trends in the SFA content of meat and milk will be suggested.     

Quantitative structure-property relationships for normal saturated and unsaturated fatty acids

Quantitative structure-property relationships, a technique of deriving properties of compounds from knowledge of their structures, has been applied to aliphatic carboxylic acids, an industrially important group of compounds. Equations have been developed from the molecular connectivity of the first order and the molar refraction as inputs which, on testing with data of seven properties, yielded average absolute deviations ranging between 0.9 and 6.7%. The compounds studied ranged between C₁ and C₃₀ for saturated and C₃ to C₂₂ for unsaturated fatty acids. The properties studied are normal melting and boiling points, critical temperature and pressure, and heats of fusion, combustion and formation.     

Influence of dietary saturated fatty acids on the regulation of plasma cholesterol concentration

The specific effects of individual fatty acids (FA) on plasma cholesterol levels, in the range habitually consumed by humans, is not usually presented by the literature. Conclusions have been made regarding the cholesterolemic effect of individual FA, even though these FA cannot be tested individually. It appears that FA balance of the diet may be more important than individual FA intakes. Variation in plasma cholesterol response to diet is influenced by many factors, such as gene-nutrient interactions. The effect on human health of current processes used in the food industry that are certain to change dietary fat composition and TG structure is yet to be fully explored. Some of the relevant research regarding dietary fat and plasma cholesterol levels is reviewed.     

Esterification rates of some saturated and unsaturated fatty acids with glycerol

Esterification rates of eight commonly occurring fatty acids were studied at 180C using equivalent and equimolar amounts of glycerol with and without a cosolvent. The esterification with equivalent amounts of glycerol without cosolvent followed second order kinetics and proceeded at a similar rate for all acids examined. Esterifications with equimolar amounts of glycerol were kinetically complex and their speed depended on the solubility of glycerol in individual fatty acids.     

Effect of ingestion of isomeric fatty acids on cholesterol and lipids of serum and liver

The effect of the ingestion of large amounts of thetrans, trans isomer of linolein upon the cholesterol and lipid levels of the blood and liver was investigated using hypercholesterolemic rats. The serum levels of esterified fatty acids and cholesterol of rats fed the diets containing 30% oftrans, trans linoleic acid glycerides and safflower oil were 15 and 25%, respectively, lower than those fed coconut oil. However, a weight loss associated with less intake of thetrans isomer as compared with a gain with the other two fats must be considered. The serum levels of labeled cholesterol of rats administered radioactive cholesterol along with thetrans isomer were intermediate in maximum value as compared to the levels obtained with coconut and safflower oils. These results suggest that thetrans isomers are not as effective as thecis isomers in lowering the cholesterol and lipids of the blood. The livers of the former group had a lower fat content than the latter which might be accounted for in part by the lower fat intake Presented at AOCS Meeting, Houston, Texas, 1965.