Determination of trans fatty acids in cold pressed oils and in dried seeds

The adulteration of cold pressed oils (CPO) by refining or by blending with refined oils leads to an increase in their trans fatty acid (TFA) contents. The regulations of the European Union (EU) lay down strict processing conditions without any steam treatment for native olive oils and provide limits for TFA. However, German regulations allow a ''steam washing'' for CPO other than native olive oil and do not limit TFA. Thus, the TFA contents of such oils might exceed the limits for native olive oil. Modern capillary GLC serves as a quick tool for the detection of TFA. However, care should be taken to avoid the formation of TFA as artefacts during analysis. We evaluated the TFA contents in several oils labelled as ''cold pressed'' and the formation of TFA during ,,steam washing'' and deodorization. Analysis of some seeds indicates that preliminary drying of the seeds may also contribute to TFA content.