Aldehyde‐Amine Condensation Reaction: A Possible Fate of Carbonyls in Foods

Abstract

SUMMARY The reaction rate of L‐tyrosine ethyl ester with π‐heptanal was determined at 10, 20, 30, and 40°C by following the change in optical rotation. The reaction‐rate data indicate that two consecutive first‐order reactions occur. The apparent energies of activation for the first and second reactions were calculated to be 5.8 and 6.4 kcal, respectively. Infrared spectral data suggest the presence of the imine linkage in the product. Colored pigments of the reaction of glycine with n‐heptanal were fractionated, but the fractions were not pure enough for further study. Alk‐2‐enals were the only class of carbonyls noted in the nitrogen‐free pigments. A mechanism consistent with the available experimental information is proposed for the removal of carbonyls with simultaneous formation of unsaturated‐polymeric pigments in foods.