Exploring polymerisation of 1,2-dicarbonyl compounds to decipher the formation of nitrogen-free substructures in melanoidins

Abstract

• MGO or 3-DG can be reacted under different pH conditions to form polymers. • MW of the structural units of the polymers was mainly 54 ± 2 or 72 ± 2 Da. • Polymers can be cross-linked with gluten and dextran to form macromolecules. • Polymers are the nitrogen-free substructure in melanoidins. • Polymers can be used as candidate biomarkers. To decipher the formation mechanism of nitrogen-free substructures in melanoidins, methylglyoxal or 3-deoxyglucosone was used as a substrate to react by aldol reaction under different pH conditionst. The obtained products were characterised by chromatography, mass spectrometry, and spectroscopic methods. Overall, the molecular weights of the polymers structural units varied mainly within 54–56 and 72–74 Da, respectively, due to the different dehydration extent of β-hydroxy aldehyde or ketones, and uneven reduction by NaBH 4 . Moreover, the nitrogen-free substructures formed by this reaction can cross-link with gluten and dextran to form melanoidins. Therefore, the nitrogen-free substructures by this reaction to formed with units of 54–56 and 72–74 Da, which are similar as the typical polymers in food melanoidins. It is inferred that the typical polymers in food may also be formed by this pathway and which can be used as a detectable biomarker in melanoidins.