An improved GC method for the rapid separation of positional
and geometrical isomers of fatty acid methyl esters has been
developed. The resolution of cis and trans isomers was better in
comparison with previous reports, especially for elaidic and oleic
acid. Its application to the analysis of fatty acids in frying palm oil and
chicken fillets has been shown to be robust and reliable. The results
showed that the rate of isomerization and thermal degradation of
PUFA was drastically higher at the elevated temperatures tested,
forming larger amounts of components with potential harmful
health effects. This suggested that an increase in frying temperature
above 200 C can cause intensive isomerization of PUFA. Besides, by
respective monitoring of TFAs accumulation in frying materials and
frying oil, we found that trans 18:3 FAs could be released from the
chicken fillets to the oil, and similarly the elaidic acid could be
transferred from frying oils to chicken fillets. These results indicated
that the trans level in frying materials and the frying oils can affect
each other due to fast exchange of fats during frying. In addition, this
developed method may be used for the labeling and quality control
of food which contains specific fatty acid profiles.