反刍动物源和工业源反式脂肪酸的摄入对心脏代谢风险标志物的影响

反式脂肪酸(TFA)主要来源于氢化植物油和反刍动物(瘤胃中通过生物氢化途径合成)源食品。人类膳食中总反式脂肪酸的摄入量与心血管代谢疾病危害因子的升高和心血管疾病的发展紧密相关。但有关工业源反式脂肪酸(iTFA)与反刍动物源反式脂肪酸(rTFA)对心血管代谢疾病危害因子影响的差异仍存争议。鉴于此,本研究查阅国内外有关反式脂肪酸对心血管代谢疾病影响的最新研究成果,在综合考虑研究对象性别、年龄、反式脂肪酸摄入量以及食物营养构成等因素的基础上,系统分析工业源和反刍动物源反式脂肪酸的摄入量对成人心血管代谢疾病危害因子的影响。结果表明:两种来源的反式脂肪酸都会增加心血管疾病代谢风险因子,反刍动物源反式脂肪酸对心血管疾病代谢风险的影响要高于工业源反式脂肪酸,并且对女性的影响要高于对男性的影响。此外,引起风险的大小除了与TFA来源有关外,还与性别、摄入量以及膳食结构存在紧密的关系。建议加大对不同人群、不同膳食模型条件下反式脂肪酸对心血管疾病风险影响的研究,为指导并制定我国居民膳食中反式脂肪酸的允许安全摄入量提供科学依据。     

国内外对膳食反式脂肪酸的研究概况

反式脂肪酸是植物油经过部分氢化处理过程中产生的,所以通常又被称为氢化植物油。它在加工食品和餐厅中经常被使用,以改善口感、延长保质期或增添香味等。已有研究证明反式脂肪酸与心血管疾病、Ⅱ型糖尿病、婴幼儿发育等息息相关。就反式脂肪酸的定义、来源、主要危害、各国限量标准、分析方法等进行综述。     

反式脂肪酸的研究进展

本文对反式脂肪酸的结构、来源、摄入量、生理作用和检测方法等进行综述。研究表明日常食用的人造奶油、起酥油和焙烤食品中存在大量反式脂肪酸,它们主要是在油脂的氢化过程中产生的。天然的反式脂肪酸主要是在反刍动物的瘤胃菌作用下产生的,存在于乳制品中,含量较低;乳制品中主要的反式脂肪酸—18∶111t,已证实可在体内转化为对人体有益的18∶29c11t。反式脂肪酸能提高冠心病和Ⅱ型糖尿病的发病率,并且干扰不饱和脂肪酸代谢、影响婴儿的生长。人们对不同来源的反式脂肪酸的生理作用还存在争议,反式脂肪酸的作用可能与其异构体种类有关。     

从油脂加工控制反式脂肪酸

随着氢化油的大量使用,反式脂肪酸的危害逐渐显现。过量摄入反式脂肪酸会增加心血管疾病的危险性、诱导血栓形成,还能干扰脂肪酸代谢,影响青少年儿童的生长和智力发育。近年来,公众对反式脂肪酸的担忧越来越强。本文综述了反式脂肪酸的产生、来源及对人体的危害。反式脂肪酸有两个来源,天然存在和油脂加工过程中产生,其危害主要来自油脂氢化、精炼及煎炸过程产生的反式脂肪酸。因此,本文提出主要从以下3个方面控制反式脂肪酸:(1)寻找氢化油的替代品:酯交换油脂、酯化产品、油凝胶、棕榈油分提物等;(2)采用油脂提取新技术:水酶法提油、冷榨提油、超临界萃取提油等;(3)减少煎炸。旨在从源头把关,从根本上消除反式脂肪酸可能引起的健康隐患。     

如何限制油脂反式脂肪酸含量和摄入量

反式脂肪酸对人体有一定的负面作用,如引发冠心病、导致乳腺癌、影响必需脂肪酸的消化吸收等.反式脂肪酸存在于精炼油脂和氢化油脂中,为了减少油脂中反式脂肪酸的含量,应采用合适的设备、并控制油脂精炼过程中的脱臭条件,对于氢化油脂还需要控制氢化条件、选择合适的氢化油原料.通过低温、短时间的脱臭可以使精炼油脂中反式脂肪酸含量降到最低.另外,建议我国有关食品立法部门规定对反式脂肪酸加以标识,以正确引导消费.     

低反式脂肪酸油脂替换高反式脂肪酸油脂的研究

我们日常食用的很多食品中存在不同程度的反式脂肪酸.一些焙烤和油炸食品如油饼、丹麦馅饼,深度油炸食品如炸鸡、炸土豆条等,以及假奶酪、人造奶油、冰淇淋、糖果中的反式脂肪酸含量可能较高,其中有很大部分是由于加工时使用了部分氢化油脂所致,也有的是加工过程中由于热作用产生的,它们的反式脂肪酸含量大都随加入的氢化油量的不同而存在较大差异.当煎炸油或加工原料中含有较多的反式脂肪酸时,产品中便会有较多的反式脂肪酸存在.传统的油脂氢化方法是在镍催化下,将氢气直接加成到脂肪酸不饱和位点处,对植物油脂或动物油脂进行部分氢化,高温、高压的催化条件能导致TFA的大量产生.传统的氢化工艺产生的反式脂肪酸较多,但通过控制工艺参数可一定程度上降低反式脂肪酸的形成量. 现在许多国家都已经将食品中的反式脂肪酸含量写入食品标签,美国FDA的规定已于2005年1月正式启用,即每份食品中的反式脂肪酸含量大于5％时,须在标签中标明.而我国在反式脂肪酸的研究方面还远远落后于国际,还没有关于反式脂肪酸含量的相应标准.     

GC-MS法检测食品中反式脂肪酸的研究进展

反式脂肪酸是指含一个以上独立反式构型双键的不饱和脂肪酸.食品中的反式脂肪酸主要来源于氢化植物油.科学研究表明摄入过量的反式脂肪酸可能会对机体造成不良的健康影响.能够增加患心脏病、冠心病、乳腺癌的几率,同时还有抑制幼儿生长发育的负面作用.本文介绍了反式脂肪酸的性质、来源、危害及GC-MS分析方法研究进展.     

植物油的营养和如何在加工中减少反式酸

介绍了油脂脂肪酸对人体的关系及反式脂肪酸对人体的负面作用。在油脂加工过程中,反式酸含量的增加主要在脱臭工段和氢化工段,为了降低油脂中反式脂肪酸含量,在脱臭段设计填料和板式相结合的脱臭塔,要控制操作条件。在我国间歇氢化过程中,反式酸增加量超过20%,要总结影响因素并加以控制反式酸的含量。超声波氢化、电化学催化氢化和生物酶技术可以减少油脂中反式酸含量。     

轻度氢化对精炼巴沙鱼油品质影响

该文研究了轻度氢化对精炼巴沙鱼油品质的影响,主要包括风味稳定性、氧化稳定性、反式脂肪酸、固体脂肪含量、过氧化值和酸值。结果显示:轻度氢化可以明显提高精炼巴沙鱼油的风味稳定性和氧化稳定性;对固体脂肪含量影响较大;对过氧化值有一定的降低作用,但与氢化程度无关;对酸值无明显影响;轻度氢化后反式脂肪酸含量有所增加,但与碘值下降程度不呈确定关系。虽然轻度氢化后反式脂肪酸含量增多到2.5%左右,但远远低于氢化油反式脂肪酸含量20%的平均值。     

反式脂肪酸生成机理的研究

反式脂肪酸的危害越来越被人们所熟知。反式脂肪酸的形成机理也各不相同。食品中的反式脂肪酸主要来自于反刍动物代谢过程中生成与食品加工过程中形成的反式结构的脂肪酸。反刍动物体内的反式脂肪酸是由氢化细菌-丁酸弧菌酶促氢化作用下形成。植物油氢化工艺中,在金属催化剂参与下产生反式异构体。在高温烹调条件下,发现反式脂肪酸含量不断增加,通过量子化学密度泛函理论推导(能量计算)与试验验证相结合,发现在150°或更高的温度下油酸发生异构化生成反式油酸。     

高分辨率反式脂肪酸测定方法的建立及市售食用油反式脂肪酸的测定

本文建立了高分辨率的反式脂肪酸测定方法,并考察了市售食用油的反式脂肪酸含量及其种类的情况。结果表明:采用高极性的色谱柱HP-88在优化后色谱条件下,可以实现4种亚油酸异构体、8种亚麻酸异构体、37种常见脂肪酸良好的色谱分离,而且反式脂肪酸与常见的顺式脂肪酸在同时检测条件下出峰时间不重叠,可以进行高分辨率的脂肪酸包括反式脂肪酸组成分析;市售主要品种的食用油都存在一定量的反式脂肪酸,其中调和油、花生油、大豆油含有2~3%的反式脂肪酸(反式亚麻酸含量在1.5~2%之间);玉米油和葵花籽油中反式亚油酸的含量在0.7~2%之间;稻米油的反式脂肪酸的含量最高,接近4%;橄榄油和山茶油的反式脂肪酸含量一般在0.5%以下;各油样的反式脂肪酸异构体的种类也存在区别。     

反式EPA/DHA的来源、检测技术与生理功能研究进展

反式脂肪酸是脂肪酸链上至少含有1个非共轭反式双键的不饱和脂肪酸异构体。反式脂肪酸（C18）会提高血液胆固醇水平,增加心血管疾病的风险,给人体造成不利的影响。EPA/DHA是重要的长链多不饱和脂肪酸,具有多种生物活性,对维持人体健康具有重要意义。EPA/DHA在精炼加工过程中会发生反式异构化。与全顺式EPA/DHA相比,反式EPA/DHA的生理功能发生了显著变化。从反式EPA/DHA的来源、检测技术、生理功能等方面进行了综述,以期为EPA/DHA的综合开发利用提供科学依据和理论基础。     

酸碱对大豆油脂中反式脂肪酸的影响

以常规加热为对照组,通过气相色谱法分析H3PO4处理或NaOH处理对非共轭亚油酸(C18∶2)的热诱导顺/反异构化的分子机制。由加热试验可知,C18∶2-9c,12t和C18∶2-9t,12c为加热大豆油脂中的主要反式异构体。随着加热温度逐渐升高、加热时间的逐渐增强,反式亚油酸含量随之增加。3种油样加热后产生反式脂肪酸的量的排序为:NaOH处理后油样>H3PO4处理后油样>未处理油样。在加热过程中,生成单反式亚油酸的量高于生成双反式亚油酸的量。在温度260℃加热8 h时,经NaOH处理的加热油脂产生的单反式亚油酸(C18∶2-9c,12t)最多,达1.222%。通过Gauss软件对油脂中的双键进行分析,可知常规加热形成C18∶2-9t,12t需要跨越能量分别为235.986,223.846 kJ/mol两个能垒,而当油脂进行H3PO4处理或NaOH处理后产生的反式亚油酸的能垒降低,表明H3PO4处理或NaOH处理均会增加加热油脂反式异构体的几率,其中NaOH处理的影响最大。     

TRANS FATTY ACID CONTENT OF SOME FOOD PRODUCTS IN POLAND

The fatty acid composition of chips, cakes and ice creams was determined with particular attention to their trans fatty acid content. The trans C18:1 content was determined by a combined capillary gas-liquid chromatography (GLC) and silver thin-layer chromatography (Ag-TLC). Six of ten types of chips examined contained more than 10% trans C18:1 (in the range of 10.3 to 17.3% of the total fatty acids), and the other four had below 0.5%. In the lipids of cakes trans C18:1 isomers occurred at 1.49 to 41.44% and only four types of cakes contained less than 5% of trans C18:1. The cis-trans and trans-cis C18:2 isomers were present among the fatty acids of the majority of chips and cakes investigated. Six types of chips contained trans-trans C18:2 in the 1.2–1.6% range. Trans fatty acids were absent in the lipids of 6 types of ice cream, but two types contained 11.3 and 19.4% trans C18:1.     

银离子固相萃取法测定反刍动物反式脂肪酸异构体含量

利用氨丙基硅胶柱从反刍动物脂质中分离甘油三酯和磷脂,以氢化大豆油作为对照。采用银离子固相萃取柱分离甘油三酯和磷脂中反式脂肪酸异构体,气相色谱仪测定反式脂肪酸含量。结果显示:在3种反刍动物脂质中检测出trans-16:1,trans-18:1和trans18:2 3类反式脂肪酸,其中总脂质和甘油三酯总反式脂肪酸含量最高的是羊肉脂质,分别占总脂肪酸的7.64%和7.38%;磷脂中总反式脂肪酸最高的是牛肉脂质,占总脂肪酸的5.89%。银离子固相萃取柱能够从反刍动物脂质中分离出9种trans18:1异构体,其中含量最高的是11t18:1,分别为总脂质、甘油三酯和磷脂trans18:1的30.33%~39.03%,38.08%~45.09%和27.10%~44.47%。通过PLS-DA分析3种反刍动物反式脂肪酸异构体之间的差异,羊肉脂质中甘油三酯中的9t18:1和磷脂中的11t18:1含量均显著高于牛奶脂质和牛肉脂质(P<0.05);牛肉脂质中磷脂中的9t18:1和15t18:1含量均显著高于牛奶脂质和羊肉脂质(P<0.05);牛奶脂质磷脂中的12t18:1和16t18:1的含量均显著高于牛肉脂质和羊肉脂质(P<0.05)。反刍动物磷脂中的反式脂肪酸异构体有较大差异。     

EFFECTS OF DIETARY 18:3 N-3 TRANS ISOMERS ON THE Δ6 DESATURATION OF α-LINOLENIC ACID

Trans isomers of polyunsaturated fatty acids (PUFA) are formed during heat treatment of oils. In the present work, the effect of dietary geometrical isomers of α-linolenic acid (18:3 n-3) on the Δ6 desaturation of all cis 18:3 n-3 was investigated, using rat liver microsomes. The desaturation rates were higher in microsomes from animals fed a cis n-3 deficient diet, as compared to those from the control group or those from rats fed 18:3 n-3 and its trans isomers. These data and the incorporation of long chain trans PUFA in microsomal lipids suggest that geometrical isomers of 18:3 n-3 are probably slowly desaturated and elongated into long chain trans polyunsaturated fatty acids compared to 18:3 n-3.     

载气类型对气相色谱法分离顺-反脂肪酸异构体的影响

采用气相色谱-火焰离子化检测器,CP-Sil88毛细管柱为分析柱,考察在不同载气（氦气和氮气）和不同加热温度（等温180 ℃和梯度升温）条件下对不同食品基质中C18:1、C18:2和C18:3顺-反脂肪酸异构体分离度和定量的影响。结果显示,以氦气为载气,在起酥油、黄油、饼干和蛋糕4 种食品基质中,C18:1 13t,14t(6-8c)和C18:1 9c的分离度大于1.0,可清晰分辨并准确定量不同浓度C18:1的4t～13t,14t异构体,不会低估C18:1反式脂肪酸异构体总量。在植物油中,载气类型对C18:2顺反异构体的分离度和含量无影响;相比氮气,氦气在C18:3顺反异构体分离上具有一定优越性,但总量无显著差异。氦气作为同时测定食品中的反式脂肪酸、饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸的载气,定量准确且样品适用性广。     

The composition of bovine milk lipids: January 1995 to December 2000

Data from recent publications on bovine milk lipids are presented and discussed. This includes extraction of lipids, triacylglycerols, phospholipids, other complex lipids, sterols, isoflavones, and fatty acids. Improved gas-liquid and high performance liquid chromatography were used. Data on the trans and cis isomers of fatty acid and of conjugated linoleic acids are given, and the analyses are described. Papers about the lipids in milks and dairy products from the United States are few; where with the exception of trans-fatty acid isomers and conjugated linoleic acids, almost no research has been reported.     

Occurrence of trans-C18:1 fatty acid isomers in goat milk: effect of two dietary regimens

Trans-octadecenoic acid composition of goat milk fat was studied by using silver-ion thin layer chromatography combined with gas-liquid chromatography. This analytical procedure also was used to investigate the effect of diet on trans-C18:1 fatty acid content in goat milk. Thirty-two goats were used in a 2 x 2 factorial arrangement and treatments. Two groups of goats received alfalfa hay at either a high or a low level of forage and two other groups received Rumiluz (dehydrated alfalfa from France Luzerne, Chalon en Champagne, France) at either a high or a low level of forage. Trans-C18:1 isomer proportions (relative to total fatty acids) were, respectively, 2.02% for the Rumiluz low-level group and 1.75% for the Rumiluz high-level group versus 1.71% for the alfalfa low-level group and 1.21% for the alfalfa high-level group. Goats fed on Rumiluz thus produced relatively higher levels of trans-C18:1 fatty acids than animals fed alfalfa hay. The results also showed that production of trans-C18:1 fatty acids increased when the level of forage in the diet decreased. Moreover, goat milk trans-C18:1 composition appeared similar to the cow milk profile. Vaccenic acid, trans-11-C18:1, was the major component and represented about 36.2% of total trans-C18:1 isomers.     

An implementation of central composite design: Effect of microwave and conventional heating techniques on the triglyceride composition and trans isomer formation in corn oil

Triglyceride composition and trans fatty acid content of corn oil subjected to microwave and conventional heating were evaluated with the aid of central composite design methodology. Oil samples with and without α-tocopherol were prepared on the basis of central composite design and, the effects of the main three factors (temperature, contact time, and the amount of α-tocopherol) were tired to investigate 10 at different five levels. Linoleic acid-linoleic acid-linoleic acid content in triglyceride structure of corn oil and the amount of trans fatty acids in the same oils were taken as response values for evaluation of central composite design assays. Based on the response surface, the optimum conditions (at which trans fatty acid formation and the change in the triglyceride composition are minimum) were determined for both heating procedures. The results showed that the increasing of the temperature and contact time increased the trans fatty acid formation and changed triglyceride structure of the oil in both heating techniques, although, the addition of α-tocopherol at high concentration caused pro-oxidant effect on triglyceride composition (bad effect), while reducing the formation of trans fatty acid (good effect). The results revealed that the heating 20 treatments caused significant changes in the triglyceride composition and trans fatty acid isomers of unsaturated fatty acids of the oil, while the saturated fatty acid contents did not change substantially. These alterations were much greater in microwave-heated samples (trans fatty acid ≤ 7.26%) than in Q3 corresponding samples heated in a conventional stove (trans fatty acid ≤ 0.56%).