To determine trans fatty acid (TFA) distribution of contemporary foods, especially regarding individual trans octadecenoic acids (trans C18:1), 339 German foods of six categories (semi-solid fats, deep-fried potato products, bakery products, confectioneries, instant products and butter) were analysed using two GC methods. Results showed a high variation of TFA content between and within the categories containing between 0 and 40.5% of FAME except in butter, which is a source of natural TFA. The mean TFA values were below 2.0% of FAME, however, bakery products contained 4.5% and butter fat 3.2%, respectively. In addition, the distribution of individual trans C18:1 differed. In samples containing ruminant fat (butter and various confectioneries), vaccenic acid (t11-C18:1, t11) predominated, while in foods containing industrially hydrogenated fats, elaidic acid (trans-9, t9-) and t10-C18:1 were the major trans isomers.. This was reflected by a low t9/t11 index of 0.3 and 0.5 in butter and ruminant fat containing confectioneries, respectively, whilst the highest index was observed in shortenings and deep-fried potato products at 5.2 and 6.8, respectively. In conclusion, the TFA content of foods available on the German market is generally declining, but substantial variations are present. The t9/t11 index could be used as an indicator to determine ruminant fat. Practical applications: A number of studies provide evidence that a high TFA intake, particularly of industrial origin, adversely affects human health. The TFA content of foods could be reduced due to the introduction of several mandatory regulations and modifications regarding the hydrogenation process of oils. The most abundant dietary TFA are the isomers of trans C18:1. Unfortunately, the differentiation of these isomers is not yet very common, though the trans C18:1 profile differs depending on its origin (bacterial hydrogenation in the rumen or industrial hydrogenation). To date, data for TFA content including the trans C18:1 profile of different food categories are limited. The present study confirmed that the TFA contents in German foods are declining. However, TFA are still elevated, especially in bakery products and confectioneries, which are produced using mainly industrial but also ruminant fats. Therefore, the t9/t11 index imparts important information on the source of TFA in processed foods.

中文翻译：

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含脂肪食品中的反式脂肪酸异构体和反式 9/反式 11 指数

确定当代食品的反式脂肪酸 (TFA) 分布，尤其是单个反式十八碳烯酸 (trans C18:1)，6 类 339 种德国食品（半固体脂肪、油炸马铃薯制品、烘焙食品、糖果、速溶食品）产品和黄油）使用两种 GC 方法进行分析。结果表明，除黄油之外，FAME 含量介于 0 至 40.5% 之间的类别之间和内部的 TFA 含量差异很大，黄油是天然 TFA 的来源。平均 TFA 值低于 FAME 的 2.0%，然而，烘焙产品分别含有 4.5% 和 3.2% 的黄油脂肪。此外，个体反式 C18:1 的分布不同。在含有反刍动物脂肪（黄油和各种糖果）的样品中，异油酸（t11-C18:1，t11）占主导地位，而在含有工业氢化脂肪的食品中，反式酸（trans-9, t9-）和 t10-C18:1 是主要的反式异构体。在起酥油和油炸马铃薯产品中观察到的指数分别为 5.2 和 6.8。总之，德国市场上食品的 TFA 含量普遍下降，但存在很大差异。t9/t11 指数可作为测定反刍动物脂肪的指标。实际应用：许多研究提供的证据表明，摄入过多的反式脂肪酸，尤其是工业来源的，会对人类健康产生不利影响。由于引入了一些关于油加氢过程的强制性法规和修改，食品中的 TFA 含量可能会降低。最丰富的膳食 TFA 是反式 C18:1 的异构体。不幸的是，这些异构体的区分还不是很常见，尽管反式 C18:1 的特征因来源（瘤胃中的细菌氢化或工业氢化）而异。迄今为止，包括不同食品类别的反式 C18:1 在内的 TFA 含量数据是有限的。目前的研究证实，德国食品中的反式脂肪酸含量正在下降。然而，TFA 仍然升高，特别是在主要使用工业脂肪和反刍动物脂肪生产的烘焙产品和糖果中。因此，t9/t11 指数提供了有关加工食品中 TFA 来源的重要信息。1 型材因其来源（瘤胃中的细菌氢化或工业氢化）而异。迄今为止，包括不同食品类别的反式 C18:1 概况在内的 TFA 含量数据是有限的。目前的研究证实，德国食品中的反式脂肪酸含量正在下降。然而，TFA 仍然升高，特别是在主要使用工业脂肪和反刍动物脂肪生产的烘焙产品和糖果中。因此，t9/t11 指数提供了有关加工食品中 TFA 来源的重要信息。1 型材因其来源（瘤胃中的细菌氢化或工业氢化）而异。迄今为止，包括不同食品类别的反式 C18:1 在内的 TFA 含量数据是有限的。目前的研究证实，德国食品中的反式脂肪酸含量正在下降。然而，TFA 仍然升高，特别是在主要使用工业脂肪和反刍动物脂肪生产的烘焙产品和糖果中。因此，t9/t11 指数提供了有关加工食品中 TFA 来源的重要信息。尤其是烘焙产品和糖果，它们主要使用工业脂肪和反刍动物脂肪生产。因此，t9/t11 指数提供了有关加工食品中 TFA 来源的重要信息。尤其是烘焙产品和糖果，它们主要使用工业脂肪和反刍动物脂肪生产。因此，t9/t11 指数提供了有关加工食品中 TFA 来源的重要信息。