Amine‐malonaldehyde condensation products and their relative color contribution in the thiobarbituric acid test

Different malonaldehyde‐amine condensation products were tested for their relative color contribution to the thiobarbituric acid (TBA) test, an indicator for oxidative rancidity of polyunsaturated lipids. The open chain mono‐ and disubstituted malonaldehyde (M) addition products (R‐N=CH‐CH=CHOH and R‐N=CH‐CH=CH‐NH‐R) gave complete (100%) recovery of M on a mole basis. When the M residue was incorporated into cyclic products which formed between the ureido‐ or guanidino‐ substituents of α‐amino acids such as citrulline or arginine and M , recovery of M by the TBA color test was 30% and 6%, respectively. Products, from imine‐amine type interactions, containing the M residue as in pyrazoline or pyrazole ring systems, released from 4% to no M .