Revealing the heat-induced cis-trans isomerization of unsaturated fatty acids in camellia oil

Abstract

The regularity of cis-trans isomerization of unsaturated fatty acids in camellia oil under heating was revealed adopting fatty acid profile evolution coupled with reaction kinetics. The temperatures of generating mono-trans linoleic acids (C18:2-9c12t and C18:2-9t12c) and linolelaidic acid (C18:2-9t12t) were at 220 °C and 280 °C respectively, both of which were significantly higher than that of elaidic acid (180 °C). And the total trans fatty acids (TFAs) content was increased with the elevating of heating temperature. Furthermore, the reaction rate constants (k) of cis-trans isomerization were observed according to the rate equations. In accordance with the k, the activation energy (Ea) of the cis-trans isomerization was calculated referring to the Arrhenius equation, the Ea of generating elaidic, mono-trans linoleic and linolelaidic acids reactions were 97.22 kJ/mol, 127.4 kJ/mol and 112.6 kJ/mol, respectively. These results indicated that oleic acid is more prone to be converted into trans isomer than linoleic acid, the mono-trans linoleic acids are the precursors of linolelaidic acid in heat-induced camellia oil. This study provides a reference for the potential inhibition of TFAs formation during camellia oil processing.