Molecular structure characteristics and pyrolytic volatiles of hydrosoluble colored fractions from three melanoidins

The melanoidins produced by the Maillard reaction give foods a golden, brown or black color and release aromatic compounds. Investigating the molecular structure and pyrolysis characteristics of melanoidins provides insight into improving food quality. Seven hydrosoluble colored fractions were isolated from three melanoidins (glycine/glucose (Gly-Glc), proline/glucose (Pro-Glc), and phenylalanine/glucose (Phe-Glc)) using size exclusion and C18 chromatography. Fractions with lower molecular weights (Mw: 5958- 20,106 Da) exhibited deeper colors (browning index: 0.783-3.044). For melanoidins derived from polar amino acids (glycine), low-polarity fractions contributed more to color, while for those from non-polar amino acids (proline), high-polarity fractions were more significant. Mass spectrometry revealed consistent polymerization patterns involving glyoxylic acid and glyoxal across fractions (mass-to-charge differences of 74 m/z and 58 m/z). NMR analysis indicated that Pro-Glc fractions contained more glucose skeletons, whereas Phe-Glc fractions exhibited benzene-ring features. After pyrolysis, furans, pyrroles, and cyclopentenones were major volatiles in Gly-Glc fractions, with pyrroles and DDMP dominating Pro-Glc fractions, and phenyl-containing compounds prevalent in Phe-Glc fractions. These findings suggest amino acids influence both melanoidin structure and glucose-derived skeletons, providing a foundation for controlling color and aroma formation during processing such as baked foods, roasted meats, coffee, dairy products and fermented foods.