Trans fatty acids in refined and deodorized oils

2 Trans fatty acids in refined and deodorized oils 

These trans compounds have different physical properties than natural cis isomers and are readily separated with gas chromatography analysis. The detection of trans isomer fatty acids in an olive oil indicates addition of seed oils to olive oil, of refined olive oil to virgin olive oil and of esterified oil to residue olive oil and olive oil. 

Gas chromatography is the most accurate means of quantifying the trans isomers present in fatty acid mixtures. In the GC trace the trans peaks appear broader because they contain isomers whose complete resolution is difficult. Virgin olive oils may show, in the sum of the trans-oleic acid-isomers, a maximum value of 0.05% and in the sum of /ran.v-linoleic and linolenic acid the same maximum value of 0.05%. Lower grade olive oils and refined olive oils are allowed wider limits for fatty acid trans isomers (see Table 2.2). 

A number of alternative methods are available for determining /ram-isomers, including spectroscopy, both infrared (IR) and Raman, and nuclear magnetic resonance (NMR) (Firestone and Sheppard, 1992). 

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