The analysis of trans fatty acid profiles in deep frying palm oil and chicken fillets with an improved gas chromatography method

• 52 kinds of fatty acids have been separated simultaneously.
• Higher temperature leads to drastic isomerization of PUFA.
• The peak elution sequence is Rt Cn < Rt Cn + 1,2,3 …; Rt trans-Cn < Rt cis-Cn.
• A fast exchange of FAs is found between chicken fillets and the oil.

An improved gas chromatography method for the simultaneous separation of 52 fatty acids (FAs) has been developed. For both oleic acid and linoleic acid, a good resolution was achieved for their positional and geometrical (cis/trans) isomers. This method was validated to be precise, accurate and sensitive. With this method, the FAs profiles in palm oil and chicken fillets were analyzed. In general, small changes were observed in the composition of FAs and formation of trans isomers after 8 h frying at the temperature lower than 200 °C. However, with extreme deep-frying process, the thermal degradation and TFAs formation in frying oil increased in direct proportion to frying temperature and time. Moreover, the FAs composition of fried chicken fillets was found to be mostly in correspondence with that of the frying oil, which might be due to the oil absorption or interaction between the frying oils and frying materials.