Studies on the TBA test for rancidity grading: II. TBA reactivity of different aldehyde classes

Abstract

The TBA reactivities of several aldehydes, most of them known as ordinary products of lipid autoxidation, have been investigated systematically. Gas liquid chromatography-purified alkanals, 2-alkenals and 2,4-alkadienals were reacted with TBA in water solution. The formation of pigments with maximum absorbance at 450 and 530 nm was measured at optimum time-temperature conditions-different for readings at 450 and 530 nm- and values for absorbance per mole aldehyde were calculated. These values show that on reaction with TBA all studied aldehydes build a yellow 450 nm pigment, while only 2,4-alkadienals and, to a lesser extent, 2-alkenals produce the red 530 nm pigment. Consequently both pigments are measures of aldehydic products of lipid autoxidation: In the case of predominant unsaturated aldehyde formation, determination of the pigment with maximum absorbance at 530 nm is preferable. However, if alkanals are predominant, the determination of the yellow pigment at 450 nm is more apporpriate, as it grants higher sensitivity.