Milk fatty acid

One frozen dessert is made with Simplesse, a protein-based fat mimetic that contains no fat (37). Other dairy product developments include a fat flavor, produced by encapsulating milk fatty acids in maltodextrins (38) fat-free cottage cheeses and 2% fat milk, prepared by steam stripping cream with partial fat addback, with a cholesterol level about 60% lower than the starting material (39). 

Saturated fatty acids (no double bonds), such as myristic, palmitic, and stearic, make up two-thirds of milk fatty acids. Oleic acid is the most abundant unsaturated fatty acid in milk, with one double bond. Triglycerides account for 98% of milk fat. The small amounts of mono-, diglycerides, and free fatty acids in fresh milk may be... 

Laiho, K., Lampi, A. M., Hamalainen, M., Moilanen, E., Piironen, V., Arvola, T., Syrjanen, S., and Isolauri, E. (2003). Breast milk fatty acids, eicosanoids, and cytokines in mothers with and without allergic disease. Pediatr. Res. 53, 642-647. 

Synthesis of fatty acids via the malonyl CoA pathway does not proceed beyond palmitic acid (C16 0) and mammary tissue contains an enzyme, thioacylase, capable of releasing the acyl fatty acid from the carrier protein at any stage between C4 and C16. Probable interspecies differences in the activity of thioacylase may account for some of the interspecies differences in milk fatty acid profiles. 

The application of several chromatographic procedures to the separation and identification of milk lipids was mainly responsible for these endeavors. The first gas-liquid chromatographic (GLC) analysis of milk fatty acids was published by James and Martin (1956). By 1960, many laboratories were using GLC for routine analysis of fatty acids. For example, Jensen et al. (1962) reported the fatty acid compositions of 106 milk samples taken during 1 year. In comparison, Hansen and Shorland (1952) analyzed only six samples in a year, using distillation of methyl esters. 

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... 

Gas liquid chromatography is still the method of choice for the routine separation and tentative identification of common milk fatty acids, as well as for the resolution of the less abundant and less common acids. Although several hundred fatty acids are listed here and elsewhere as being present in milk, we remind the reader that not all of these have been rigorously identified. Some of the pitfalls in qualitative and quantitative GLC of milk fatty acids are discussed by Jensen et al. (1967) and those of fatty acids in general by Ackman (1980). 

Iverson and Sheppard (1977) have compared the method above, substituting sodium butoxide for sodium methoxide to H2S04 and boron trifluoride-catalyzed butyrolyses. Butyl esters were used by these and other investigators to improve the resolution of short chain esters and to reduce their volatility. They recommend the boron trifluoride method for preparation of butyl esters of milk fatty acids, although the other catalysts gave satisfactory results. Analysis of methyl esters resulted in lower values for the short chain fatty acids. 

The results from the analyses of milk fatty acids as butyl esters by Jensen et al. (1962), Parodi (1970) and Iverson (1983) are remarkably consistent, considering that the analyses were widely separated by time and distance. The differences in quantities between June and December reflect the influence of season, that is, the availability of pasture. Determination of butyl esters as described by Iverson and Shep-... 

Cyclohexylundecanoic acid has been isolated from bovine milk and characterized (Schogt and Haverkamp Begemann 1965). Brewington et al. (1974) found glucuronides of 17 milk fatty acids in bovine milk. These were presumably detoxification products formed in the liver and, interestingly, included the odd-chain acids, 9 0-17 0. 

Smith, S. 1980. Mechanism of chain length determination in biosynthesis of milk fatty acids. J. Dairy Sci. 63, 337-352. 

Gonthier, C., Mustafa, A.F., Ouellet, D.R., Chouinard, P.Y., Berthiaume, R., and Petit, H.V. 2005. Feeding microionized and extruded flaxseed to dairy cows Effects on blood parameters and milk fatty acid composition. J. Dairy Sci. 88, 748-756. 

Ward, A.T., Wittenberg, K.M., and Przybylski, R. 2002. Bovine milk fatty acid profiles produced by feeding diets containing solin, flax and canola. J. Dairy Sci. 85, 1191-1196. 

Wright, S. and Bolton, C.H., Breast milk fatty acid composition in mothers of children with atopic eczema, Br. J. Nutr., 62, 693, 1989. 

Hermansen, J.E. (1995) Prediction of milk fatty acid profile in dairy cows fed dietary fat differing in fatty acid composition. J. Dairy Sci., 78, 872-879. 

Chen, S., Bobe, G., Zimmerman, S., Hammond, E.G., Luhman, C.M., Boylston, T.D., Freeman, A.E., Beitz, D.C. 2004. Physical and sensory properties of dairy products from cows with various milk fatty acid compositions. J. Agric. Food Chem., 52, 3422-3428. 

Iverson, S.J., Arnould, J.P.Y., Boyd, I.L. 1997. Milk fatty acid signatures indicate both major and minor shifts in diet of lactating Antarctic fur seals. Can. J. Zool., 75, 188-197. 

Forty to sixty per cent of milk fatty acids are long-chain (predominantly Ci 8) fatty acids derived from the diet, dependent on the amount of fat in the diet. Fatty acids from C4 to C14 are synthesized de novo in the mammary gland whereas Ci6 arises from both diet and de novo synthesis. 

Future advances in the science of milk fat and nutrition will come from focusing on the unique biological properties of minor milk fatty acids arising from ruminal biohydrogenation and possibly some of de novo mammary origin. 

Acyl chain length (Ci6 vs Cis) influences the proportions of these in milk fat the effects of are more subtle because of compensation by reduced de novo synthesis of Ci6 o when long-chain fatty acids are supplemented in the diet. Palmitic acid was increased from 45% of milk fatty acids to 53% when a high (68%) Ci6 o supplement was added to a low-fat diet. 

Similarly, supplementing soy oil (90% Cis) increased the total Qg of milk fat from 25% to 60% of milk fatty acids. Yields of Q, to C14 were reduced by both supplements, whereas the yield of Ci6 o was increased by palm oil and reduced by soya oil (Banks et al., 1976) these effects are typical (Noble et al., 1969). Similarly, supplementing increasing amounts of coconut oil (high in Ci2 o and Ci4 o) increased the proportions of these in milk fat and reduced the proportions and yields of short-chain fatty acids and Ci6 o (Storry et al., 1971). 

Oleic acid was increased to 48% of total milk fatty acids by feeding oleamide as a rumen-protected source of oleic acid (Jenkins, 1998). The response was nearly linear up to 5% of supplement in the diet dry matter. Proportions of all de uovo-synthesized milk fatty acids, except butyric, were reduced (Jenkins, 1999). LaCount et al. (1994) abomasally infused fatty acids from canola or high oleic acid sunflower oil into lactating cows. The transfer of oleic acid to milk fat was linear (slope = 0.541 0 350 g infused/ day) the proportion of oleic acid in milk fat increased and proportions of all de novo-synthesized fatty acids, except C4 and C6 decreased. The proportion of Ci8 o also was unchanged. Linoleic acid from canola also was transferred linearly (slope = 0.527 0-90 g infused/day). These transfers from the intestine are nearly identical to that reported by Banks et al. (1976). Hagemeister et al. (1991) reported 42 to 57% transfer of abomasally-infused linolenic acid to milk fat. 

Feeding for Specific Milk Fatty Acid Profiles... 

The earliest efforts to modify the composition of milk fat used an insoluble formaldehyde-crosslinked protein to encapsulate unsaturated vegetable oils. In numerous studies using this approach, linoleic acid was increased to as high as 35%, w/w, of the total milk fatty acids (reviewed by McDonald and Scott, 1977). Bitman et al. (1973) fed increasing amounts of safflower oil encapsulated in formaldehyde-treated casein. The content of milk fat increased linearly from 3.5 to 4.6% as supplemental protected oil was increased from 0 to 1320 g/day per cow. The concentration of linoleic acid increased to 33% of total milk fatty acids, with a compensating decrease in Ci6 o and a smaller decrease in Ci4 0. The concentration of milk fat decreased to lower than pretreatment levels when the supplement was removed, a common observation (Pan et al., 1972). A typical milk fatty acid profile from cows fed a protected sunflower/soybean (70/30) supplement is shown in Table 2.1. 

Figure 2.8. Changes in proportions of milk fatty acids relative to control treatments with increasing supplementation of fats or oilseeds A. C4 to Ci4 o B. Ci6 o C. Cig o + C18 1. (From Grummer, 1991, J.Dairy Sci. 74, 3244-3257).

Shingfield, K.J., Ahvenjarvi, S., Toivonen, V., Arola, A., Nurmela, K.V.V., Huhtanen, P., Griinari, J.M. 2003. Effect of dietary fish oil on biohydrogenation of fatty acids and milk fatty acid content in cows. Anim. Sci. 77, 165-179. 

Bauman, D.E., Lock A.L., Corl B.A., IpC., Salter A.M., Parodi P.W. 2005. Milk fatty acids and human health potential role of conjugated linoleic acid and trans fatty acids. In Ruminant Physiology Digestion, Metabolism and Impact of Nutrition on Gene Expression, Immunology and Stress. (K. Sejrsen, T. Hvelplund, and M.O. Nielsen, eds.), pp. 523-555, Wageningen Academic Publishers, Wageningen, The Netherlands. Academic Publishers. 

Chouinard, P.Y., Corneau, L., Barbano, D.M., Metzger, L.E., Bauman, D.E. 1999a. Conjugated linoleic acids alter milk fatty acid composition and inhibit milk fat secretion in dairy cows. /. Nutr. 129, 1579-1584. 

Loor, J.J., Herbein, J.H. 2001. Alterations in blood plasma and milk fatty acid profiles of lactating Holstein cows in response to ruminal infusion of a conjugated linoleic acid mixture. Anim. Res. 50, 463 476. 

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