Conjugated linoleic acid of foods originated from ruminant animals and its precursor in feeds

共轭亚油酸(CLCs)是亚油酸的异构体，近年来在食品中作为生物活性物质越来越受到重视。在各种CLA异构体中，在牛肉中发现的9顺，11反CLA(9c，11t CLA)已被证明具有抗突变和降低血清胆固醇活性等有益作用。本研究的目的是建立一种准确、重复性好的测定9c，11t共轭亚油酸的方法，并用该方法测定各种肉类中9c，11t共轭亚油酸的含量，评价饲喂不同饲料的反刍动物肉中9c，11t共轭亚油酸的含量，考察加热、储存和脂肪氧化对肉中9c，11t共轭亚油酸含量的影响，从而阐明饲料脂肪中是否存在亚麻酸作为9c，11t共轭亚油酸的前体。反刍动物的肉比非反刍动物的肉含有更多的9c，11t共轭亚油酸。饲喂高粗饲料日粮的反刍动物的肉和脂肪显著高于高精料日粮饲喂的反刍动物。此外，结果还表明，粗饲料脂肪中亚麻酸的含量可能会影响肉类和脂肪中9c，11t共轭亚油酸的含量。结果还表明，肉和肉制品中的9c，11t共轭亚油酸可能对热处理、贮藏和脂肪氧化有很高的稳定性，即使在肉和肉制品的脂质过氧化过程中形成9c，11t共轭亚油酸，其产率也可能很小。在瘤胃液与亚麻酸盐的孵化中。后者异构化为9c，11t，15c十八碳三烯酸。结果还表明，9C，11T，CLA可能是通过氢化9C，11T，15C十八碳三烯酸制得的。

Conjugated linoleic acids (CLCs) are isomers of linoleic acid which have recently gained importance as one of the biologically active substances in food. Among the various CLA isomers, the 9cis,11trans CLA (9c,11t CLA) found in beef has been shown to have beneficial effects such as antimutagenic and serum cholesterol-lowering acitivities etc.. The objectives of this study are to develop a precise and reproducible method for determining 9c,11t CLA, to determine the 9c,11t CLA contents in various meats by using this developed method, to evaluate the 9c,11t CLA contents in meats from ruminants fed different feeds, to investigate the effects of heating, storage and lipid oxidation on 9c,11t CLA contents in meats, and then to elucidate wethere linolenic acid in feed lipids serves as a precursor of 9c,11t CLA or not .We have devolved a capillary gas liquid chromatographic method for determining 9c,11t CLA in meat. Meat from ruminants contained considerably more 9c,11t CLA than meat from nonruminants. Meat and fat from the high roughage ration-fed ruminants were significantly higher than those from the high concentrate ration-fed ruminants. In addition, the results suggested that the amount of linolenic acid in roughage lipids may affect the 9c,11t CLA content of meats and fats. The results also suggested that 9c, 11t CLA in meat and meat products might be highly stable against heat treatment, storage and lipid oxidation, and that its yield may be quite a small even if 9c,11t CLA should be formed during the progress of lipid peroxidation in meat and meat products. In the incubation of rumen liquor with linolenate. The latter is isomerized to 9c,11t,15c octadecatrienoic acid. The results also suggested that 9c, 11t, CLA might be formed via a rout of hydrogenating 9c,11t,15c octadecatrienoic acid.