Fournier Véronique, Juanéda Pierre, Destaillats Frédéric, Dionisi Fabiola, Lambelet Pierre, Sébédio Jean-Louis, Berdeaux Olivier
UMR FLAVIC Department, INRA, 17 Rue Sully BP 86510, 21065 Dijon, Cedex, France.
J Chromatogr A. 2006 Sep 29;1129(1):21-8. doi: 10.1016/j.chroma.2006.06.089. Epub 2006 Aug 7.
Addition of long-chain polyunsaturated fatty acids (LC-PUFAs) from marine oil into food products implies preliminary refining procedures of the oil which thermal process affects the integrity of LC-PUFAs. Deodorization, the major step involving high temperatures, is a common process used for the refining of edible fats and oils. The present study evaluates the effect of deodorization temperature on the formation of LC-PUFA geometrical isomers. Chemically isomerized eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were used as reference samples. Fish oil samples have been deodorized at 180, 220 and 250 degrees C for 3 h and pure EPA and DHA fatty acid methyl esters (FAMEs) were chemically isomerized using p-toluenesulfinic acid as catalyst. FAMEs prepared from fish oil were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). Geometrical isomers produced by both processes were fractionated by silver-ion thin-layer chromatography (Ag-TLC) and silver-ion high-performance liquid chromatography (Ag-HPLC). The FAME fractions were subsequently analyzed by gas chromatography (GC) on a 100 m highly polar cyanopropylpolysiloxane coated capillary column, CP-Sil 88. Our results show that thermally induced geometrical isomerization appears to be a directed reaction and some ethylenic double bond positions on the hydrocarbon chain are more prone to stereomutation. Only minor changes were observed in the EPA and DHA trans isomers content and distribution after deodorization at 180 degrees C. The analyses of EPA and DHA isomer fractions revealed that it is possible to quantify EPA geometrical isomers by GC using the described conditions. However, we notice that a mono-trans isomer of DHA, formed during both chemical and thermal treatments, co-elute with all-cis DHA. This feature should be taken into consideration for the quantification of DHA geometrical isomers.
将海洋油中的长链多不饱和脂肪酸（LC-PUFAs）添加到食品中意味着要对该油进行初步精炼程序，而热加工过程会影响LC-PUFAs的完整性。脱臭是涉及高温的主要步骤，是用于食用油脂精炼的常见工艺。本研究评估了脱臭温度对LC-PUFA几何异构体形成的影响。化学异构化的二十碳五烯酸（EPA）和二十二碳六烯酸（DHA）用作参考样品。鱼油样品在180、220和250℃下脱臭3小时，使用对甲苯亚磺酸作为催化剂对纯EPA和DHA脂肪酸甲酯（FAMEs）进行化学异构化。由鱼油制备的FAMEs通过反相高效液相色谱（RP-HPLC）进行分离。通过银离子薄层色谱（Ag-TLC）和银离子高效液相色谱（Ag-HPLC）对两种过程产生的几何异构体进行分离。随后在100 m高极性氰丙基聚硅氧烷涂覆的毛细管柱CP-Sil 88上通过气相色谱（GC）对FAME馏分进行分析。我们的结果表明，热诱导的几何异构化似乎是一个定向反应，烃链上的一些烯双键位置更容易发生立体异构化。在180℃脱臭后，EPA和DHA反式异构体的含量和分布仅观察到微小变化。对EPA和DHA异构体馏分的分析表明，使用所述条件通过GC可以定量EPA几何异构体。然而，我们注意到，在化学和热处理过程中形成的DHA单反式异构体与全顺式DHA共洗脱。在定量DHA几何异构体时应考虑这一特性。
