Milk phospholipids

Table 4.10. Fatty Acid Composition (Mole %) of Various Bovine Milk Phospholipids.9...

Hay and Morrison (1971) did not neglect the alkyl and alkenyl ethers in milk phospholipids, finding 4% of the latter in phosphatidylethanolamine and 1.3% in phosphatidylcholine. Trans isomers were not found. The authors postulated that the branched chain compounds in the alkenyl ethers were derived from rumen microbial lipids. 

Barbano and Sherbon (1981) found that feeding cows a protected poly unsaturated fat supplement had little influence on the fatty acid composition of the milk phospholipids. The biosynthesis of the pools of fatty acids from which milk phospholipids are synthesized is apparently independent of dietary input. 

Barbano, D. M. and Sherbon, J. W. 1981. Polyunsaturated protected lipid Effect on milk phospholipids. J. Dairy Sci. 64, 2170-2174. 

Patton, S. and Keenan, T. W. 1971. The relationship of milk phospholipids to membranes... 

The positional distribution of the fatty acids in two phospholipids, phosphatidylcholine and phosphatidylethanolamine, in bovine and human milk is described in Table 1.13 (Christie, 1995). The fatty acids in bovine milk phospholipids have a lower degree of unsaturation than those in human milk phospholipids. However, the distribution of fatty acids between the two positions is similar. Polyunsaturated fatty acids are attached preferentially at the sn-2 position, the monounsaturates are distributed similarly between the two positions, and 18 0 is esterified preferentially at the sn-1 position while the other saturated fatty acids (14 0, 16 0) are distributed more evenly (bovine phosphatidylethanolamine being an exception). The phospholipids in human milk show remarkable selectivity for 18 0 at the sn-1 and 18 2 at the sn-2 positions. 

Bitman, J., Wood, D.L. 1990. Changes in milk phospholipids during lactation. J. Dairy Sci., 73, 1208-1216. 

Fagan, P., Wijesundera, C. 2004. Liquid chromatographic analysis of milk phospholipids with on-line pre-concentration. J. Chrom. A, 1054, 241-249. 

Morrison, W.R., Smith, L.M. 1967. Fatty acid composition of milk phospholipids. II. Sheep, Indian buffalo and human milks. Lipids, 2, 178-182. 

Synthesis of phosphatidylinositol follows a slightly different pathway from the other phosphoglycerides. Phosphatidate is activated by CTP-phos-phatidate cytidyl transferase to form CDP-diacylglycerol. Free inositol is then incorporated by CDP-diacylglycerol inositol transferase, with the release of CMP. Phosphatidylinositol usually constitutes less than 5% of total milk phospholipids (Bitman and Wood, 1990). 

The distribution and fatty acid composition of phospholipids in skim milk are similar to those in the MFGM. This has led to the suggestion that these membrane-associated constituents originate from a common cellular source and that the skim milk membranes, which contain much of the skim milk phospholipid pool, may be shed MFGM (for review, see Keenan and Dylewski, 1995). This assumption remains to be tested critically. 

Dial, E. J., Lichtenberger, L.M. 1984. A role for milk phospholipids in protection against gastric acid. Studies in adult and suckling rats. Gastroenterology. 87, 379-385. 

Kivinen, A., Tarpila, S., Salminen, S., Vapaatalo, H. 1992. Gastroprotection with milk phospholipids a first human study. Milchwissenschaft. 47, 694-696. 

The composition of the milk phospholipids is also an important factor in the structure and transport of lipids in both human and bovine milk. The phospholipids are found predominately in the milk fat globule membrane. 

Cows milk LPL has phospholipase Ai activity (Scow and Egelrud, 1976), but its action on milk phospholipids has not been recorded. Freshly secreted goats milk has been shown to have phospholipase A activity (Long and Patton, 1978) but it is not known whether this can be attributed to the LPL of that milk. Human milk contains an acid sphingomylinase C, as well as ceramidase activity provided by the bile salt-stimulated lipase present (Nyberg et al., 1998). 

Milk phospholipids were shown to protect against stress, bacterial, and chemical-induced gastric mucosal damage. 

Mammals are dependent on dietary sources of essential fatty acids as they lack the desaturase enzymes necessary to synthesize them. Kao et al. (2006) engineered transgenic mice expressing the ffl-3 fatty acid desaturase enzyme from the nematode Caenorhabditis elegans, which synthesizes a wide range of PUFA and possesses the only known example of an ffl-3 desaturase enzyme in the animal kingdom. The milk from these mice had more ffl-3 and less ffl-6 PUFA, and hence had showed an overall decrease in the ffl-6 ffl-3 PUFA ratio in the milk. The milk phospholipids from the transgenic mice had an ffl-6 ffl-3 ratio of 1.78 as compared to 9.82 in the control animals. The authors anticipate that this maybe a suitable method to improve the nutritional profile of dairy-based diets. 

Although in fluid milk the phospholipid fraction is more susceptible to oxidation than the triacylglycerol fraction, in dry milk products, the triacylglycerol fraction is more susceptible to oxidation and the phospholipids act as antioxidants. Thus, solvent-extracted milkfat containing phosphohpids is much more stable to oxidation than milkfat free of phospholipids, obtained by melting churned butter (also called butter oil). The susceptibility of milk phospholipids to oxidation appears to be dependent on whether they are suspended in water or fat. This difference of oxidahve stability influences the development of different flavor defects in various dairy products. With butter, which is a water-in-oil emulsion system containing an aqueous phase of phospholipids dispersed in fat, the phosphohpids oxidize more readily than the triacylglycerol components. 

Morrison, W. R., and Smith, L. M. Fatty Acid Composition of Milk Phospholipids. II. Sheep, Indian Buffalo, and Human Milks Lipids 2(2) 178-182 (1967) CA 67 1330c... 

Umansky MS and Melnikova LV (1986) Influence of milk phospholipid hydrolysis products on the quality of Soviet cheese. Information Bulletin no. 195-86, Barnaul Van Bogelen RA, Kelley PM and Neidhardt FC (1987) Differential induction of heat shock, SOS, and oxidation stress regulons and accumulation of nucleotides in 5c/ierrc/i/a coli. J Bacteriol 169 26-32... 

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