Bovine milk lipids fatty acids

TABLE 5. Positional and Geometric Isomers of Bovine Milk Lipid Fatty Acids (wt. %) (16). 

Table 4.1. Fatty Acid Composition of Bovine Milk Lipids as of August 1983.

The composition and structure of bovine milk fat have been reviewed extensively. There are early reviews by Morrison (1970), Christie (1978, 1995), Jensen and Clark (1988), and Jensen and Newberg (1995) recent articles include a comprehensive review of recent research by Jensen (2002) and two book chapters by Vanhoutte and Huyghebaert (2003), and Zegarska (2003). Bovine milk lipids are similar to the milk lipids of other species as they are largely composed of triacylglycerols however, there are also minor amounts of diacyl-glycerols, monoacylglycerols, free (unesterified) fatty acids, phospholipids and... 

Few compilations of the extensive fatty acid distributions in butter fat have been made since Iverson et al. (17) reported quantitative data on 82 fatty acids that were detected by means of urea fractionation and gas-liquid chromatography (GLC) (Table 6). Table 7 provides the fatty acid composition of bovine milk lipids. 

Wonsil, B.J., Herbein, J.H., and Watkins, B.A. 1994. Dietary and ruminally derived trans-18 1 fatty acids alter bovine milk lipids. J. Nutr. 124, 556-565. 

Bovine milk fat is made up of 97-98 (wt% of total lipids) triacylglycerols accompanied by much smaller amounts of diacylglycerols (0.36%) and monoacylglyc-erols (0.03%), free cholesterol (0.31%), trace amounts of cholesteryl esters, phospholipids (0.60%), and minor amounts of free fatty acids. For reviews of the composition of bovine milk lipids, the reader is referred to Christie (4) and Jensen and Clarke (5). More than 400 fatty acids have been identified in milk fat, although it is generally accepted that 15 major and 12 minor fatty acids dominate the fatty acid spectrum. The major fatty acids found in milk are long chain (Cj. , myristic Ci6-o. palmitic Cjg., stearic Cjg.j, oleic) and the minor fatty acids are short chain... 

Table 16.3 Total fatty acid composition of bovine milk lipids...

Milk fats, especially ruminant fats, contain a very wide range of fatty acids more than 400 and 184 distinct adds have been detected in bovine and human milk fats, respectively (Christie, 1995). However, the vast majority of these occur at only trace concentrations. The concentrations of the principal fatty acids in milk fats from a range of species are shown in Table 3.6. Notable features of the fatty acid profiles of milk lipids include ... 

Timmen and Dimick (1972) characterized the major hydroxy compounds in milk lipids by first isolating the compounds as their pyruvic ester-2,.6-dinitrophenylhydrazones. Concentrations as weight percent of the compounds from bovine herd milk lipids were 1,2-DGs 1.43, hydroxyacylglycerols 0.61, and sterols 0.35. Lipolysis tripled the DG content. The usual milk fatty acids were observed, except that the DGs lacked 4 0 and 6 00, again indicating that these lipids were in part intermediates in milk lipid biosynthesis. With the large hydrazone group... 

Phospholipids. The phospholipids comprise approximately 1 % of the total lipid in bovine milk (ca.0.3 to 0.4 g/liter). While quantitatively minor, the ability of the phospholipids to form stable colloidal suspensions or emulsions in aqueous solution cause them to be important in the formation and secretion of milk fat. (Long and Patton 1978 Patton and Keenan 1975). Their physical properties as bipolar molecules and their relatively high concentration of unsaturated fatty acids also make them an important factor to consider during the storage and... 

Smith et al. (1978) have described a procedure for the GLC determination of cis and trans isomers of unsaturated fatty acids in butter after fractionation of the saturated, monoenoic, dienoic, and polyenoic fatty acid methyl esters by argentation TLC. Total trans acids were much higher, as measured by infrared spectrophotometry than by GLC, probably because some of the acids could have two or more of the trans bonds designated as isolated by infrared spectrophotometry. Enzymatic evaluation of methylene-interrupted cis, cis double bonds by lipoxidase resulted in lower values than those obtained by GLC. The authors mention that the lipoxidase method is difficult, requiring considerable skill, and suggest that their method is suitable for the determination of the principal fatty acids in complex food lipids such as bovine milk fat. 

Breckenridge, W. C. and Kuksis, A. 1968. Specific distribution of short chain fatty acids in molecular distillates of bovine milk fat. J. Lipid Res. 9, 388-393. 

Hay, J. D. and Morrison, W. R. 1971. Polar lipids in bovine milk. III. Isomeric cis and trans monoenoic and dienoic fatty acids, and alkyl and alkenyl ethers in phosphatidyl choline and phosphatidyl ethanolamine. Biochim. Biophys. Acta 248, 71-79. 

Morrison, W. R., Jack, E. L. and Smith, L. M. 1965. Fatty acids of bovine milk glyco-lipids and phospholipids and their specific distribution in the diacylglycerophos-pholipids. J. Am. Oil Chem. Soc. 42, 1142-1147. 

Clegg (1980) reported that bovine serum and high-density lipoprotein (HDL) caused an increase in free fatty acid levels in unpasteurized bulk milk. Lipoprotein free serum, apo HDL, all individual HDL tested, and the unfractionated C-peptide fractions had no lipolytic effect. HDL-lipid in the presence of 2 C-peptides and the combination of HDL-lipid with unfractionated C-peptide caused a considerable stimulation of lipolysis. 

While bovine milk is a rich source of xanthine oxidase, milks from some species do not necessarily contain appreciable amounts of enzymatically active xanthine oxidase. For example, human milk contains only traces of xanthine oxidase activity as measured by oxidation of xanthine or hypoxanthine (Zikakis and Treece 1971 Zikakis et aL 1976), yet a band corresponding in electrophoretic mobility to xanthine oxidase is a major constituent of human milk lipid globule membrane (Freudenstein et al. 1979 Murray et cd. 1979). Evidence that the membrane-bound form of xanthine oxidase in bovine lipid globule membrane contains small amounts of tightly bound fatty acid has been obtained (Keenan et al. 1982). Whether this property promotes attraction between the membrane or membrane-associated coat and the surface of the globule core remains to be determined. 

The fatty acids of bovine milk fat arise from two sources synthesis de novo in the mammary glands and the plasma lipids originating from the feed. The fatty acids from these two sources differ in their structure. The fatty acids that are synthesised de novo are short-chain and medium-chain length acids, from 4 0 to 14 0 and also some 16 0, while the Cis fatty acids and some 16 0 arise from the plasma lipids. De novo fatty acid synthesis accounts for approximately 45% (w/w) of the total fatty acids in milk fat, while lipids of dietary origin account for the rest (Moore and Christie, 1979). 

Precht, D., Molkentin, J. 2000. Trans unsaturated fatty acids in bovine milk fat and dairy products. Eur. J. Lipid Sci. Technol., 102, 635-639. 

Among the biological lipids, few exceed bovine milk fat in the complexity of fatty acids present and triacylglycerol (TAG) structure. This, together with its importance commercially as a human food, has generated very large data bases on the synthesis and composition of milk fat. In spite of this, Jensen (2002) lamented the paucity of new information on the content of trace fatty acids and complex lipids in milk fat. 

The complex lipids in milk fat are comprised of the phosphoglycerides, phosphatidyl choline, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidylinositol and plasmalogens. Also, the non-glyceride phospholipid, sphingomyelin, occurs in important amounts (Jensen, 2002). Bitman and Wood (1990) described the distribution of phospholipid classes in bovine milk and their fatty acid composition. The phospholipids comprise about 1% and cholesterol 0.4—0.5% of the total milk fat. These occur almost completely in the milk fat globule membrane. 

Morrison, I.M., Hawke, J.C. 1977b. Positional distribution of fatty acids in the triglycerides of bovine milk fat with elevated levels of linoleic acid. Lipids. 12, 1005-1011. 

The major differences between the lipids of bovine and human milk are in fatty acid composition and triacylglycerol structure. Bovine milk contains substantial quantities of C4 o-Ci0 o, about 2% Cis 2 and almost no other long-chain polyunsaturated fatty acids. The fatty acid composition is not altered by ordinary changes in diet. Human milk contains very little C4 o-C10 o, 10-14%i (w/w of fat) Ci8 2, and small quantities of other polyunsaturates. The triacylglycerol structure differs, with much of the sn-2 position in human milk lipids occupied by C16 0 and the sn-2 position of bovine milk-fat occupied by C4 o-Ci0 o-... 

Milk fat contains a number of different lipids, but is predominately made up of triacylglycerols (TAG) (98%). The remaining lipids are diacylglycerols (DAG), monoacylglycerols (MAG), phospholipids, free fatty acids (FFA) and sterols. Milk fat contains over 250 different fatty acids, but 15 of these make up approximately 95% of the total (Banks, 1991) the most important are shown in Table 19.1. The unique aspect of bovine, ovine and caprine milk fat, in comparison to vegetable oils, is the presence of high levels of short-chain volatile FFAs (SCFFA), which have a major impact on the flavor/aroma of dairy products. Most cheeses are produced from either bovine, ovine or caprine milk and the differences of their FFA profile are responsible for the characteristic flavor of cheeses produced from such milks (Ha and Lindsay, 1991). 

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