Oils and fats

Fats and oils of vegetable and animal origin belong to the most important renewable raw materials used in the chemical industry. The fats and oils are mainly applied in human alimentation only 10% of the oils are converted into technical products. The total global market for fats and oils amounts to about 130 million tonnes. Soybean oil (31 million tonnes per year), a by-product of soybean flour production, and palm oil (31 million tonnes per year) are the most important fatty raw materials worldwide. Animal fats (22 million tonnes per year) arise as by-products of meat fabrication and processing and are used for nutrition and technical purposes. 

Fats and oils are triglycerides, triesters composed of glycerol linked to three fatty acids, as shown in the following block diagram. 

Triglycerides form by the reaction of glycerol with three fatty acids. 

The bonds that join the glycerol to the fatty acids are called ester linkages. Tristearin—die main component of beef fat—is formed from the reaction of glycerol and three stearic acid molecules. 

If the fatty acids in a triglyceride are saturated, the triglyceride is called a saturated fat and tends to be solid at room temperature. Lard and many animal fats are examples of saturated fat. On the other hand, if the fatty acids in a triglyceride are xmsaturated, the triglyceride is called an unsaturated fat, or an oil, and tends to be liquid at room temperature. Canola oil, olive oil, and most other vegetable oils are examples of xmsaturated fats. 

Identify tire triglycerides and classify each as saturated or xmsaturated. 

Since fats and oils form essential nutrient of human diet, it is necessary to identify a pure fat or to determine the proportion of different types of fat or oil mixed as adulterant in edible oils and fats like butter and ghee. With an adequate knowledge of the characteristic composition of fats or oils, it is possible to identify the fat or oil under investigation. The chemical constants also give an idea about the nature of fatty acids present in fats or oils. Eventhough gas chromatographic method is available to identify and quantify the fatty acids present in fat or oil, the physical and chemical constants are still used in routine public health laboratories where such sophisticated facilities are lacking. 

Under ordinary conditions, oils and melted fate do not mix 

Fixed oils.—These substances are designated as fixed, to distinguish them from other vegetable products having an oily appearance, but which differ from the true oils in their chemical composition and in their physical properties, especially in that they are volatile without decomposition, and are obtained by distillation, while the flxed oils are obtained by expression, with or without the aid of a gentle heat. 

Palm-oil is a reddish-yellow solid at ordinary temperatures, has a bland taste and an aromatic odor.. It saponifles readily, and is usually acid and contains free glycerol liberated by spontaneous decomposition. 

Kape-seed and colza oils, produced from various species of Jirassica, are yellow, limpid oils ha ng a strong odor and disagreeable taste. 

Croton-oil—Oleum tiglii (TJ. S.)—Oleum crotonis (Br.)—varies much in color and activity, according to its source that which is obtained from the East is yellowish, liquid, transparent, and much less active than that prepared in Europe from the imported seeds, which is darker, less fluid, caustic in taste, and wholly soluble in absolute alcohol. Croton-oil contains, besides the glj -cerids of oleic, crotonieand fatty acids, about four per cent, of a peculiar principle called crotonol, to which the oil owes its vesicating properties. It also contains an alkaloid-like substance, also existing in castor-oil, called ricinin. Kone of these bodies, however, are possessed of the drastic powers of the oil Itself. 

Triacylglycerols (fats and oils) store the majority of the energy in most animals and plants. Fats such as beef tallow remain solid or semisolid at room temperature while oils such as olive oil or corn oil are liquid at that temperature. Oils solidify only at lower temperatures—in a refrigerator, for example. The different kinds of fatty acids found in the side chains of the triacylglycerol cause the different melting temperatures. The fatty acids of oils contain more double bonds than do those of fats. 

These molecules make good energy-storing units because their oxidation releases more energy than the oxidation of carbohydrates or amino acids. The caloric density of triacylglyerols is about 9 kilocalories per gram, compared to 5 kilocalories per gram for the latter biomolecules. 

Essential fatty acids are precursors to membrane lipids and to compounds that serve as intercellular signals in animals. 

The caloric density of lipids is due to the side chain carbons of fats being more reduced (hydrogen-rich) than the side chain carbons of carbohydrates, for example  

Naturally occurring oils and fats constitute another important source of renewable raw materials [198]. Whether they are referred to as fats or oils depends on whether they are solid or liquid at room temperature, respectively. They are composed primarily of triglycerides (triesters of glycerol) together with small amounts of free fatty acids, phospholipids, sterols, terpenes, waxes and vitamins. Oils and fats are either of vegetable or animal origin and are produced in the approximate proportions 55% vegetable oils, 40% land-animal fats and 5% marine oils [199]. 

—It is interesting to know, that both of these practical applications of nitro-glycerine, viz., dynamite and gelatin powder were invented by a Swede by the name of Nobel who left his money made from the invention of these powerful explosives, for the establishment of prizes in connection with the promotion of peace and known as the Nobel Peace Prizes. 

The most important esters of this class are, the neutral or tri-acid esters of glycerol with the higher acids of the saturated and the unsdtu-rated series. The most important acids, in this connection, are given in the following list  

Butyric acid.. Caproic acid.. Caprylic acid. Capric acid... Laurie acid... Myristic acid. Palmitic acid. Stearic acid... Arachidic acid 

C3H6—COOH C16H29—COOH CnHay-COOH Acid (CfiH2n-4)02 

Constitution of Fats and Oils.—These acids which have all been previously discussed (pp. 136 and 170) embrace the more common ones that are found as esters in most oils and fats. The tri-acid ester of glycerol and palmitic acid may be taken as an example of a typical fat. It is exactly analogous to the ester of glycerol and acetic acid which we have just considered, and its formula is  

Despite the potential advantages of employing IR spectroscopy in fats and oils analysis, the only recognised application of IR spectroscopy in this area is the determination of isolated trails isomers in fats and oils by dispersive IR spectroscopy, which is an official method of the American Oil Chemists  

3 p becomes significant. The AOCS method requires that samples containing less than 15% isolated trans isomers be saponified and methylated prior to analysis. For such cases, calibration is performed with methyl elaidate in place of trielaidin. 

Peak Positions of the Functional Groups Absorptions of Reference Compounds Representative of Products Formed in Oxidised Oils 

Note a) bold face indicate functional groups involved b) All double bonds in the trans form. 

Another potential area of application of FTIR spectroscopy is in the determination of the oxidative status or stability of an oil. Autoxidation is a major deteriorative reaction affecting edible fats and oils, and it is of major concern to processors and consumers from the standpoint of oil quality, as the oxidative breakdown products cause marked off flavours in an oil. A wide range of end products are associated with the autoxidative deterioration of fats and oils, the most important being hydroperoxides, alcohols, and aldehydes. Moisture, hydrocarbons, free fatty acids and esters, ketones, lactones, furans, and other minor products may also be produced, with the free fatty acids becoming more important in thermally stressed oils. In addition, there is significant cis to trans isomerisation and conjugation of double bonds in the hydroperoxides formed as an oil oxidises. 

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The fatty acids occur in nature chiefly as glycerides see fats), which constitute the most important part of the fats and oils, and as esters of other alcohols, the waxes. The naturally occurring fatty acids are mostly the normal straight-chain acids with an even number of carbon atoms. 

CH20H-CH(0H)-CH,0H, C3HHO3. Normally obtained as a colourless, odourless, viscous liquid with a very sweet taste. M.p. 20 C, b.p. 182 C/20mm. It absorbs up to 50% of its weight of water vapour. It occurs (glycerides) in combination with various fatly acids in all animal and vegetable fats and oils. 

Colourless liquid. B.p. 286 C/100 mm., insoluble in water. Oleic acid occurs naturally in larger quantities than any other fatty acid, being present as glycerides in most fats and oils. It forms one third of the total fatty acids of cow s milk. A crude grade from inedible tallow is used in the production of lubricants, detergents, resins and other products. 

Detergents are made by, for example, treating petroleum hydrocarbons with sulphuric acid, yielding sulphonated products which are water soluble. These can also solubilise fats and oils since, like the stearate ion, they have an oil-miscible hydrocarbon chain and a water-soluble ionic end. The calcium salts of these substances, however, are soiu u-ic in water and, therefore, remove hardness without scum formation. 

Hydrocarbons are divided into two mam classes aliphatic and aromatic This classifi cation dates from the nineteenth century when organic chemistry was devoted almost entirely to the study of materials from natural sources and terms were coined that reflected a substance s origin Two sources were fats and oils and the word aliphatic was derived from the Greek word aleiphar meaning ( fat ) Aromatic hydrocarbons irre spective of their own odor were typically obtained by chemical treatment of pleasant smelling plant extracts... 

Fats and oils are naturally occurring mixtures of glycerol tnesters Fats are mixtures that are solids at room temperature oils are liquids The long chain carboxylic acids obtained from fats and oils by hydrolysis are known as fatty acids... 

Esters can participate m hydrogen bonds with substances that contain hydroxyl groups (water alcohols carboxylic acids) This confers some measure of water solubil ity on low molecular weight esters methyl acetate for example dissolves m water to the extent of 33 g/100 mL Water solubility decreases as the carbon content of the ester increases Fats and oils the glycerol esters of long chain carboxylic acids are practically insoluble m water... 

Fats and oils are naturally occurring mixtures of triacylglycerols also called triglyc erides They differ m that fats are solids at room temperature and oils are liquids We generally ignore this distinction and refer to both groups as fats... 

Acetyl coenzyme A is the biosynthetic precursor to the fatty acids, which most often occur naturally as esters Fats and oils are glycerol esters of long chain carboxylic acids Typically these chains are unbranched and contain even numbers of carbon atoms... 

Aliphatic (Section 2 1) Term applied to compounds that do not contain benzene or benzene like rings as structural units (Historically aliphatic was used to descnbe compounds de rived from fats and oils )... 

Fats and oils (Section 26 2) Tnesters of glycerol Fats are solids at room temperature oils are liquids Fatty acid (Section 26 2) Carboxylic acids obtained by hydro lysis of fats and oils Fatty acids typically have unbranched chains and contain an even number of carbon atoms in the range of 12-20 carbons They may include one or more double bonds... 

Kalbus, G. E. Lieu, V. T. Dietary fat and Health An Experiment on the Determination of Iodine Number of fats and Oils by Goulometric Titration, /. Chem. Educ 1991, 68, 64—65. 

The iodine number of fats and oils provides a quantitative measurement of the degree of unsaturation. A solution containing a 100% excess of IGl is added to the sample, reacting across the double-bonded sites of unsaturation. The excess IGl is converted to I2 by adding KI. The resulting I2 is reacted with a known excess of Na2S203. To complete the analysis the excess 8203 is back titrated with coulometrically generated I2. 

Eatty acids from commercial fats and oils, such as peanut oil, are extracted with methanolic NaOH and made volatile by derivatizing with a solution of methanol/BE3. Separations are carried out using a capillary 5% phenylmethyl silicone column with MS detection. By searching the associated spectral library students are able to identify the fatty acids present in their sample. Quantitative analysis is by external standards. 

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