SOYBEAN AND HEALTH - University of Macau Library

Conjugated Linoleic Acid: A Milk Fatty Acid with Unique Health Benefit Properties 113HHHCH 3 (CH 2 ) 5 CHC C C (CH 2 ) 7 COOHcis-9, trans-11 CLAHHHCH 3(CH 2 ) 4 C C C C (CH 2 ) 8 COOHHtrans-10, cis-12 CLAFoodstuffTotal CLA(mg/g of fat)FoodstuffTotal CLA(mg/g of fat)Dairy productsMeatsHomogenized milk 4.5 Ground beef 4.3Condensed milk 7.0 Lamb 5.6Butter milk 6.1 Pork 0.6Mozzarella cheese 4.9 Chicken 0.9Plain yogurt 4.8 Salmon 0.3Ice-cream 3.6 Ground turkey 2.5Table 1. CLA content of common foods (Chin et al., 1992)2. Biosynthesis of CLACLA found in milk and meat of ruminants originates from two sources (Griinari andBauman, 1999). CLA is formed during ruminal biohydrogenation of linoleic acid and thesecond source is CLA synthesized by animal tissues from trans-11 C 18:1 , another intermediatein the biohydrogenation of unsaturated fatty acid. Hence, the uniqueness of CLA inruminant edible products relates to incomplete biohydrogenation of dietary unsaturatedfatty acids in the rumen.2.1 CLA synthesis in the rumenDietary lipids undergo two important transformations in the rumen (Devillard et al., 2004).First, lipolysis - hydrolysis of ester linkages catalyzed by microbial lipase and second,biohydrogenation of unsaturated fatty acid.The first reaction in linoleic acid (cis-9, cis-12) biohydrogenation is isomerization of the cis-12double bond. Linoleate isomerase is the enzyme responsible for forming conjugated doublebonds from the cis-9, cis-12 double bond structure of linoleic as well as α and γ linolenicacids. The enzyme is bound to the bacterial cell membrane and demonstrates an absolute