Fatty acids in fats

Historically, many attempts have been made to systematize the arrangement of fatty acids in the glyceride molecule. The even (34), random (35), restricted random (36), and 1,3-random (37) hypotheses were developed to explain the methods nature utilized to arrange fatty acids in fats. Invariably, exceptions to these theories were encountered. Plants and animals were found to biosynthesize fats and oils very differently. This realization has led to closer examination of biosynthetic pathways, such as chain elongation and desaturation, in individual genera and species. 

TABLE 4 Fatty Acids in Fats and Fatty Oils... 

Hefner lamp chem A flame lamp that burns amyl acetate. hef-nar, lamp Hehner number analychem Weight percent of water-insol ubie fatty acids in fats and oils. han-ar, nam-bar ... 

Iverson, J. L., Eisner, J. and Firestone, D. 1965. Detection of trace fatty acids in fats and oils by urea fractionation and gas-liquid chromatography. J. Am. Oil Chem. Soc. 42, 1063-1068. 

Madison, B. L. and Hughes, W. J. 1983. Improved lipoxygenase method for measuring cis, cis-methylene interrupted polyunsaturated fatty acids in fats and oils. J. Assoc. Anal. Chem. 66, 81-84. 

Most of the fatty acids in fats are esterified with glycerol to form glycerides. However, in some fats, particularly where abuse of the raw material has occurred leading to enzymatic activity, considerable (>5%) free fatty acid (FFA) is found. Hydrolysis occurs in the presence of moisture. This reaction is catalyzed by some enzymes, acids, bases, and heat. Most producers of fats attempt to prevent the formation of free fatty acid because certain penalties are assessed if they are present in the trading of crude and refined fats. 

The methods of fractionation listed in Lewkowitsch (1904) soon led to the separation and determination of individual fatty acids in fats. These were listed in Hilditch and Williams (1964) and the values obtained for major components were usually very similar to those later determined by GC. 

Peters, H. and Wieske, Th. (1966) Detection of traces of polybranched fatty acids in fats. Fette Seif. Anstrichm., 68, 947-950. 

Jensen, S.K., Nielsen, K.N. 1996. Tocopherols, retinol, beta-carotene and fatty acids in fat globule membrane and fat globule core in cows milk. J. Dairy Res. 63, 565-574. 

Jeromin, L., Peukert, E., and Wollmann, G. 1987. Process for the pre-esterification of free fatty acids in fats and oils. United States Patent 4698186. 

AAFCO Definitions—Chemical Preservatives (Antioxidants). Antioxidants are used to retard oxidation of unsaturated fatty acids in fats, oils, and fish and meat meals, and to slow the destruction of fat-soluble vitamins, especially vitamin E. Their presence must be identified on the label when used. Use of the following compounds is permitted alone or in combination at levels not to exceed 0.02% of the fat present. 

Burr GO, Brown JB, Kass JP, Lundberg WO. Comparative curative values of unsat urated fatty acids in fat deficiency. Proc Soc Exp Biol Med 1940 44 242-244. Clarke SD. Polyunsaturated fatty acid regulation of gene transcription A molecular mechanism to improve the metabolic syndrome. J Nutr 2001 131 1129-1132. Cuthbertson WFJ. Essential fatty acid requirements in infancy. Am J Clin Nutr 1976 ... 

Acyl-CoAs are intermediates in oxidation of fatty acids, in fat synthesis, in elongation of fatty acids longer than palmitate (16 carbons), in fatty acid desaturation. 

Burr, G.O., Brown, JB.,Kass,JP., and Lundberg,W.O. (1940) Comparative Curative Values of Unsaturated Fatty Acids in Fat Deficiency, Proc. Soc. Exp. Biol. Med. 44,242-245. 

The three R groups can be the same or different groups within the same fat or oil, and they can be saturated or unsaturated. The most common fatty acids in fats and oils are listed in Table 15.2. 

Composition of oil/fat. To study the composition of oil/fat it is essential to test the purity of an oil/ fat for adulteration, accidentally or voluntarily. The specific fatty acid in fat can be determined by GC by preparing methyl esters with sodium methoxide. Mass spectrometry coupled to GC (GC-MS) is the most powerful tool for identification of fatty acids separated by GC. Free fatty acids in oil (index of rancidity) can be determined by titration against standard alkali. Infrared (IR) spectroscopy, Raman spectroscopy, and ultraviolet (UV) spectroscopy (200—400 nm) are used to detect isomers (trans and cis) of unsaturated fatty acids and conjugated double bonds. It is important to study saponification value (depict fatty acid chain length), iodine value (give the degree of unsaturation), and hydroxyl value (free fatty acids present in fats). 

Irwin, W. J. (1982) Analytical Pyrolysis A Comprehensive Guide, Marcel Dekker, New York. Ismail, A. A., van de Voort, F. R., Emo, G. and Sedman, J. (1993) Rapid quantitative determination of free fatty acids in fats and oils by Fourier transform infrared spectroscopy. Journal of the American Oil Chemists Society, 70, 335-41. 

The most abundant saturated fatty acids in fats and oils are lauric, myristic, palmitic, and stearic acids (see Table 19.7). The most abundant unsaturated acids in fats and oils contain 18 carbon atoms and have one, two, or three carbon-carbon double bonds. Their formulas are... 

Widmer, C., and Holman, R. T. 1950. Polyethenoid fatty acid metabolism. Deposition of polyunsaturated fatty acids in fat-deficient rats upon single fatty acid supplementation. Arch. Biochem. 26, 1. 

The most common saturated fatty acids in fats are the following ... 

An overview of the occurrence of saturated fatty acids in fats and oils is given in Table 3.7. Generally, the most common fatty acid is palmitic add, which occurs in virtually aU animal and plant hpids, bound in triacylglycerols and phosphohpids. 

Azizian, H. and Kramer, J.K.G., A rapid method for the quantification of fatty acids in fats and oils with emphasis on trans fatty acids using Fourier transform near infrared spectroscopy (FT-MR), Upids, 40, 855-867, 2005. 

Dionisi, F., Golay, P.A., and Fay, L.B., Influence of milk fat presence on the determination of trans fatty acids in fats used for infant formula, Analytica Chim. Acta, 465, 395-407, 2002. 

Table 8 Saturated Fatty Acids (%) in Fats and Oils... 

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