73-5 |
Changes in the DHA, CLA and trans-18:1 content in milk fat from cows fed with a diet containing fish meal |
C. CRUZ-HERNANDEZ1, J. K. G. Kramer2, and A. R. Hill1. (1) Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada, (2) Food Research Program, Agriculture and Agri-Food Canada, 93 Stone Road west, Guelph, ON N1G 5C9, Canada Beneficial health effects have been demonstrated for n-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), as well as conjugated linoleic acid (CLA). Several studies have been conducted to increase the level of these fatty acids (FAs) in milk fat. Yet, there is still limited information available on chemical and positional analyses of n-3 FAs and CLA. Our objective was to fully characterize the complete FA profile of a DHA enriched milk from cows fed with a diet containing fish meal. An attempt to relate changes in both FA composition and previously observed physical properties. Total milk fat from milk and cheese was extracted using a chloroform/methanol/water system. Fatty acid methyl esters (FAME) were prepared and analyzed by gas chromatography (GC) using a 100 m CP Sill 88 capillary column. Silver ion thin layer chromatography was combined with GC to resolve, identify, and quantify all possible positional cis and trans monoens. DHA enriched milk fats showed decreased levels of the short chain FA (C6 to C10), and increased levels of many n-3 polyunsaturated fatty acids (PUFA; 20:5n-3, 22:5n-3 and 22:6n-3), CLA and total trans 18:1 FAs. A significant increase was noted in D10trans-18:1. This isomer has been associated with milk fat depression. Stability of long chain PUFA in cheese, including DHA, during 18 months ripening was confirmed. The DHA and CLA enriched milk and cheese fats showed FA changes that reflect an improved nutritional status of this product. Good resolution and quantification of more than 100 FAME were obtained by the used chromatographic methods. Stability of long chain PUFA in cheese, including DHA, during 18 months ripening was confirmed. These results showed marked changes in the milk and cheese fatty acid composition with improved nutritional characteristics.
Session 73, Dairy Foods: Probiotics and bioactive components in milk
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