Precision of low trans fatty acid level determination in refined oils. Results of a collaborative capillary gas‐liquid chromatography study

Abstract

The results of a collaborative study by 38 laboratories were analyzed statistically to calculate the precision of a novel capillary gas-liquid chromatography (GLC) method for the determination of low levels of trans fatty acids (TFA) in edible oils. The participants came from 17 countries, mainly European, and were spread evenly between Unilever companies and external laboratories. All participants used the same GLC method, including a temperature optimization step, which is suitable for the determination of a large range of TFA levels in refined oils and fats and for the determination of total saturated fatty acid, cis mono-and cis-cis methylene-interrupted polyunsaturated fatty acid isomers. For TFA levels down to 0.5%, the collaborative study yielded values for R within that ranged from 0.08 to 0.13% (absolute values) and for R between from 0.2 to 0.4%, depending on the isomer distribution in a particular edible oil. The proposed GLC method allows reliable TFA analysis at low levels that is suitable for monitoring oil processing practices and intake control. JAOCS 75, 483-488 (1998). FIG. 1. Representative bar graph of the accepted data for one batch of soybean oil [target trans fatty acid (TFA) level 0.90%]. For each of the 38 participants, the blind duplicate results are given in adjacent bars.

Nondestructive NMR determination of oil composition in transformed canola seeds

“…Identification of cis and trans isomers is problematic with GC methods. A 38-laboratory study concluded trans acyl chain analyses of unhydrogenated seed oils can give variable results (22). This study and another (23) found that canola oil contains 1 to 4% trans acyl chains.…”

Comparison of geometrical isomerization of unsaturated fatty acids in selected commercially refined oils

“…The distribution of the C18:1, C18:2, and C18:3 acids in the starting vegetable oils is quite different. Consequently, the amounts of detectable trans FA formed during refining are different (Bruggen et al, 1998). Also, fluctuations in the conditions of industrial processing such as temperature, duration, vacuum, humidity, stripping steam dosage and different sample origin can cause variations in trans polyunsaturated FA concentrations (Tasan and Demirci, 2003;Martin et al, 2008).…”

“…This phenomenon is described in the literature (Wolff 1992) and explained by the fact that the probability for a C18:3 molecule to be isomerized during heat treatment is about 10 to 12 times high than for a C18:2 acid molecule. Bruggen et al (1998) reported that the lowest isomerization rate is observed for the monoenoic FA. For the formation of geometrical isomers of unsaturated FA to be avoided during deodorization, the temperature in the deodorizer should be 4 Sum of trans isomers were calculated as one group for the C18:3.…”

“…However, the high temperature used in this stage may induce the geometrical isomerization of unsaturated FA, such as C18:2 and C18:3 (Tasan and Demirci, 2003). During this stage, other factors which also affect the formation of trans FA include heating time, pressure and stripping steam dosage (Wolff, 1993;Bruggen et al, 1998;Martin et al, 2008). The rate of conversion also depends on the level of unsaturation of the FA molecule (Bruggen et al, 1998).…”

“…During this stage, other factors which also affect the formation of trans FA include heating time, pressure and stripping steam dosage (Wolff, 1993;Bruggen et al, 1998;Martin et al, 2008). The rate of conversion also depends on the level of unsaturation of the FA molecule (Bruggen et al, 1998). On the other hand, trans FA isomers that may be formed in vegetable oils during refining are quite different in type and level from those formed during the hydrogenation process (Ackman et al, 1974).…”