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Studies on radical intermediates in the early stage of the nonenzymatic browning reaction of carbohydrates and amino acids.
J Agric Food Chem. 1999 Feb; 47(2):379-90.JA

Abstract

Determination of the color intensity of heated mixtures of L-alanine and carbohydrate degradation products revealed furan-2-carboxaldehyde and glycolaldehyde as by far the most effective color precursors. EPR studies demonstrated that furan-2-carboxaldehyde generated colored compounds exclusively via ionic mechanisms, whereas glycolaldehyde led to color development accompanied by intense radical formation. In agreement with literature data, these radicals were also detected in heated mixtures of L-alanine and pentoses or hexoses, respectively, and were identified as 1,4-dialkylpyrazinium radical cations by EPR as well as LC/MS measurements. Studies on the mechanisms of radical formation revealed that under the reaction conditions applied, glyoxal is formed as an early product in hexose/L-alanine mixtures prior to radical formation. Reductones then initiate radical formation upon reduction of glyoxal and/or glyoxal imines, formed upon reaction with the amino acid, into glycolaldehyde, which was found as the most effective radical precursor. LC/MS measurements gave evidence that these pyrazinium radicals cations are not stable but are easily transformed into hydroxylated 1,4-dialkyl-1, 4-dihydropyrazines upon oxidation and hydrolysis of intermediate diquarternary pyrazinium ions. Besides other types of color precursors, these intermediates might be involved in the formation of colored compounds in the Maillard reaction.

Authors+Show Affiliations

Deutsche Forschungsanstalt für Lebensmittelchemie, Lichtenbergstrasse 4, D-85748 Garching, Germany. hofmann@dfa.leb.chemie.tu-muenchen.deNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

10563904

Citation

Hofmann, T, et al. "Studies On Radical Intermediates in the Early Stage of the Nonenzymatic Browning Reaction of Carbohydrates and Amino Acids." Journal of Agricultural and Food Chemistry, vol. 47, no. 2, 1999, pp. 379-90.
Hofmann T, Bors W, Stettmaier K. Studies on radical intermediates in the early stage of the nonenzymatic browning reaction of carbohydrates and amino acids. J Agric Food Chem. 1999;47(2):379-90.
Hofmann, T., Bors, W., & Stettmaier, K. (1999). Studies on radical intermediates in the early stage of the nonenzymatic browning reaction of carbohydrates and amino acids. Journal of Agricultural and Food Chemistry, 47(2), 379-90.
Hofmann T, Bors W, Stettmaier K. Studies On Radical Intermediates in the Early Stage of the Nonenzymatic Browning Reaction of Carbohydrates and Amino Acids. J Agric Food Chem. 1999;47(2):379-90. PubMed PMID: 10563904.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Studies on radical intermediates in the early stage of the nonenzymatic browning reaction of carbohydrates and amino acids. AU - Hofmann,T, AU - Bors,W, AU - Stettmaier,K, PY - 1999/11/24/pubmed PY - 2000/9/19/medline PY - 1999/11/24/entrez SP - 379 EP - 90 JF - Journal of agricultural and food chemistry JO - J Agric Food Chem VL - 47 IS - 2 N2 - Determination of the color intensity of heated mixtures of L-alanine and carbohydrate degradation products revealed furan-2-carboxaldehyde and glycolaldehyde as by far the most effective color precursors. EPR studies demonstrated that furan-2-carboxaldehyde generated colored compounds exclusively via ionic mechanisms, whereas glycolaldehyde led to color development accompanied by intense radical formation. In agreement with literature data, these radicals were also detected in heated mixtures of L-alanine and pentoses or hexoses, respectively, and were identified as 1,4-dialkylpyrazinium radical cations by EPR as well as LC/MS measurements. Studies on the mechanisms of radical formation revealed that under the reaction conditions applied, glyoxal is formed as an early product in hexose/L-alanine mixtures prior to radical formation. Reductones then initiate radical formation upon reduction of glyoxal and/or glyoxal imines, formed upon reaction with the amino acid, into glycolaldehyde, which was found as the most effective radical precursor. LC/MS measurements gave evidence that these pyrazinium radicals cations are not stable but are easily transformed into hydroxylated 1,4-dialkyl-1, 4-dihydropyrazines upon oxidation and hydrolysis of intermediate diquarternary pyrazinium ions. Besides other types of color precursors, these intermediates might be involved in the formation of colored compounds in the Maillard reaction. SN - 0021-8561 UR - https://www.unboundmedicine.com/medline/citation/10563904/Studies_on_radical_intermediates_in_the_early_stage_of_the_nonenzymatic_browning_reaction_of_carbohydrates_and_amino_acids_ L2 - https://doi.org/10.1021/jf980626x DB - PRIME DP - Unbound Medicine ER -