Fatty acids, from natural oils unsaturated

There are essentially four steps or unit operations in the manufacture of fatty acids from natural fats and oils (/) batch alkaline hydrolysis or continuous high pressure hydrolysis (2) separation of the fatty acids usually by a continuous solvent crystallisation process or by the hydrophilisation process (J) hydrogenation, which converts unsaturated fatty acids to saturated fatty acids and (4) distillation, which separates components by their boiling points or vapor pressures. A good review of the production of fatty acids has been given (1). 

Most naturally occurring fats and oils are mixtures of triglycerides containing a variety of saturated and unsaturated fatty acids. Even the individual triglycerides are often mixed, containing two or three different fatty acids. In general, oils from plants and cold-blooded animals contain more unsaturations than fats from warm-blooded animals. Table 25-2 gives the approximate composition of the fatty acids obtained from hydrolysis of some common fats and oils. 

The fat in beef, mutton, milk, and cheese contains 2-8% trans fatty acids. These naturally occurring trans fatty acids are formed in the rumen of the stomach (of ruminants) by the action of bacterial enzymes. Most of the trans fatty acids of the diet arise from the industrial hydrogenation of food oils. During this process, most of the unsaturated cis fatty acids are converted to saturated fatty acids, but a fraction is converted to trans fatty acids. In relation to all fatty acids present in the indicated food, salad oils contain 8-17% trans fatty acid, shortening contains 14-60%, and margarines 16-70% (Simopoulos, 1996). Overall, about 6% of our dietary fatty acids are trans fatty acids, where most of these are elaidic acid (McKeigue, 1995). 

Laurie acid is a fatty carboxylic acid isolated from vegetable and animal fats or oils. For example, coconut oil and palm kernel oil both contain high proportions of lauric acid. Isolation from natural fats and oils involves hydrolysis, separation of the fatty acids, hydrogenation to convert unsaturated fatty acids to saturated acids, and finally distillation of the specific fatty acid of interest. 

Clarity at or below ambient room temperature is the primary characteristic of a liquid oil. Natural vegetable oils that are liquid at room temperatures in temperate climates, 75 5°F (23.4 3°C), contain high levels of unsaturated fatty acids with low melting points. Fatty acids with one or more double bonds and 18 carbon atoms are the most important unsaturated fatty acids for liquid oils. Oleic (18 1), a monounsaturated fatty acid, is the most widely distributed and most stable Ci8 unsaturated fatty acid. Linoleic (18 2) and linolenic (18 3) are the most widely distributed di- and triunsaturated fatty acids. Both of these polyunsaturated fatty acids are termed essential because they cannot be synthesized by animals, including man, and must be supplied in the diet. Complete exclusion of the essential fatty acids from the diet results in scaly skin, loss of weight, kidney lesions and eventually death. 

One of our major areas of development was the synthesis and study of the chromatographic (8-10), spectroscopic (11-14), and spectrometric properties of a large number of heteroaromatic fatty acid derivatives (each containing either a furan, pyrrole, thiophene, selenophene, or tellurophene nucleus). These fatty acid derivatives were obtained by total synthesis or by partial synthesis from polyunsaturated unsaturated fatty acids (12,13,15-18) and unsaturated hydroxylated fatty acids, such as ricinoleic acid (from castor oil) (19-24). In this range of heteroaromatic fatty acid derivatives, only fatty acids containing a furan nucleus are found in nature (lipid extracts of the pike and salmon and from the latex of the rubber plant) (25-29). A typical method for the preparation of a disub-... 

The process of destraction dates back to a discovery by Kurt Zosel (1913-1989) at the Max-Planck-Institut fur Kohlenforschung in Miilheim, who was engaged in normal-pressure polymerisation of ethylene. He had incidentally noticed, that residues from the distillation of oU, but also waste oil, vegetable fats and oils from natural products, could be extracted very well with supercritical gases. [514] This methodology offered correspondingly a number of other applications, as to extract hop aroma from hops, unsaturated fatty acids from fish oUs, vitamin E from vegetable oils, and paraffins or phenols from bituminous tar. 

The procedure is employed for two purposes. It separates straight-chain acids from branched-chain or cyclic compounds with the former normally concentrating in the adduct and the latter normally in the mother liquor. It has thus been used to concentrate branched-chain and cyclic acids in natural mixtures particularly when these are present only as trace constituents and to isolate cyclic acids prepared from polyene acids. One report, for example, describes the isolation of cyclic acids produced from linseed oil by high-temperature reaction with alkali in 90-95% yield and 95% purity. Urea fractionation is also used to separate adds or esters of differing unsaturation and is an important step in the isolation of pure oleic, linoleic, and linolenic acids from natural sources (Section 4.7). For example, the mixed fatty acids of cod liver oil containing 21% of n — 3 adds (mainly 18 4, 20 5 and 22 6) form an 85% concentrate of these adds (in 25% yield) after a single treatment with urea. 

The commercial exploitation of sperm oil has led to the depletion of whale populations and is banned in some countries. Attention has, therefore, turned to the jojoba plant whose oil also consists of wax esters. Most fatty chemicals obtained from natural sources have chain lengths of Cig-Cig. The limited availability of compounds with 12-14 carbon atoms, which are important in surfactants, was one of the driving forces behind the development of petrochemical processes for the production of fatty alcohols. Higher alcohols, such as C20-C22 alcohols, can be produced from rapeseed oils rich in erucic acid and fish oils. Unsaturated fatty alcohols may be manufactured in the presence of selective catalysts. 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

Carboxylate soaps are most commonly formed through either direct or indirect reaction of aqueous caustic soda, ie, alkaH earth metal hydroxides such as NaOH, with fats and oils from natural sources, ie, triglycerides. Fats and oils are typically composed of both saturated and unsaturated fatty acid molecules containing between 8 and 20 carbons randomly linked through ester bonds to a glycerol [56-81-5] backbone. Overall, the reaction of caustic with triglyceride yields glycerol (qv) and soap in a reaction known as saponification. The reaction is shown in equation 1. 

Cobalt in Driers for Paints, Inks, and Varnishes. The cobalt soaps, eg, the oleate, naphthenate, resinate, Hnoleate, ethyUiexanoate, synthetic tertiary neodecanoate, and tall oils, are used to accelerate the natural drying process of unsaturated oils such as linseed oil and soybean oil. These oils are esters of unsaturated fatty acids and contain acids such as oleic, linoleic, and eleostearic. On exposure to air for several days a film of the acids convert from Hquid to soHd form by oxidative polymeri2ation. The incorporation of oil-soluble cobalt salts effects this drying process in hours instead of days. Soaps of manganese, lead, cerium, and vanadium are also used as driers, but none are as effective as cobalt (see Drying). 

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