CP-MAS 13C NMR spectral study of the kinetics of melanoidin formation

Abstract

The kinetic parameters of melanoidin formation in the Maillard non-enzymatic browning reaction between D(+)-glucose and aminobutanoic acid isomers have been defined using cross-polarisation-magic angle spinning (CP-MAS)¹³C nuclear magnetic resonance (NMR) spectroscopy. The melanoidins were isolated from heated (313, 343 and 371 K) alkaline solutions (1.5 M, pH 9.0) of reaction mixtures after reaction periods varying from 1.08 × 10⁵ to 3.60 × 10⁵ s. The CP-MAS ¹³C NMR spectra of melanoidins showed an increase in unsaturation and aromaticity with time and temperature, and yielded more non-dialysable melanoidin fractions and more pyrrole and pyrazine derivatives as reaction intermediates.

The approximate constant, K_t, Arrhenius activation energy, E_a, and other thermodynamic values of the examined reaction step were determined.