AbstractAcid‐heat treatment is not necessary for the condensation of TBA with malonaldehyde nor for maximum colour development. Free malonaldehyde is produced during the oxidative breakdown of unsaturated fatty acids or food products. The amount of free malonaldehyde produced can be measured without acid‐heat treatment.The reaction between malonaldehyde and TBA in water or 90% glacial acetic acid has been investigated at different temperatures. The results show that acid‐heat treatment of the reaction mixture should be avoided, since the E530M of the coloured complex is considerably affected by the acid. On the contrary, heating without acid accelerates the condensation of TBA with malonaldehyde without affecting the E530M.A modification of the distillation method is proposed, according to which distillates of food products are reacted with TBA without the use of any acid.