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The Maillard reaction is well known for producing antioxidant compounds alongside colored substances. Low-molecular-weight antioxidant intermediates such as maltol (MAL) or norfuraneol (NF) are well described, but it is still unclear which of these Maillard intermediates are the precursors of antioxidant and colored melanoidins—the so-called late stage Maillard reaction products. This study aimed to provide novel insights into the correlation between browning potential and antioxidant properties of reaction products formed during the heat treatment of prominent Maillard reaction intermediates. It was achieved by the incubation of binary reaction systems composed of methylglyoxal (MGO) or NF in combination with furfural (FF), MAL, and pyrrole-2-carbaldehyde (PA) at pH 5 and 130 °C for up to 120 min. Overall, it could be shown that the formation of colored products in the binary NF reaction systems was more efficient compared to those of MGO. This was reflected in an increased browning intensity of up to 400% and a lower conversion rate of NF compared to MGO. The colorants formed by NF and FF or PA (~0.34 kDa and 10–100 kDa) were also found to exhibit higher molecular weights compared to the analogue products formed in the MGO incubations (<0.34 kDa and 10–100 kDa). The incorporation of NF into these heterogenous products with FF and PA resulted in the preservation of the initial antioxidant properties of NF (p < 0.05), whereas no antioxidant products were formed after the incubation of MGO. [ABSTRACT FROM AUTHOR]

The reaction pathways of amino acids and reducing sugars are now fully understood. The focus in the last few years, however, has turned to the reaction of peptides and proteins with reducing sugars. We have investigated the reaction of γ-aminobutanoic acid, the heptapeptide Nα-Acetyl-Lys-Lys-β-Ala-Lys-β-Ala-Lys-Gly, and the model protein β-casein in Maillard reactions with 1-13C arabinose. Characterization of 13C-labeled acetic acid and norfuraneol by gas chromatography–mass spectrometry and nuclear magnetic resonance revealed new formation pathways. The results demonstrate significant differences in the labeling pattern of the products depending on the amine used, indicating different formation pathways of acetic acid and norfuraneol. [ABSTRACT FROM AUTHOR]