It is well established that a wide range of reductones is formed in the course of the Maillard reaction and that these substances contribute to the oxidative stability of food. The aim of this study was to analyze twelve important heterocyclic intermediates with and without reductone structure as well as structural related substances under equal conditions to compare their antioxidant properties in detail. For this purpose, five methods were selected including photometrical methods like the trolox equivalent antioxidant capacity assay and an electron paramagnetic resonance spectroscopic method. Reductones with furan-3-one structure and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one were reducing in all assays while isomaltol and maltol did not react in assays based on the reduction of metal ions because of their complexing abilities. The introduction of protecting groups to the free hydroxyl functions of selected reductones could nearly eliminate their reducing abilities. In addition, the oxidation products of the different reductive heterocycles were compared after treatment with iodine. Mainly short-chained organic acids like lactic, glycolic and glyceric acid are formed as result of the degradation which indicate 1,3-dicarbonyl cleavage reactions of corresponding tricarbonyl compounds as intermediates of the oxidation.
Melanoidins
are formed in foods during processing through the Maillard
reaction between carbohydrates and amino compounds. The aim of this
study was to draw conclusions about the formation mechanism and the
structure of melanoidins formed at low water contents and low temperatures.
In the Maillard reaction of d-glucose and γ-aminobutyric
acid at low water contents 3-deoxyglucosone is the most important
intermediate. Therefore, we used the reaction of 3-deoxyglucosone
with γ-aminobutyric acid or β-alanine as a simplified
model system. The degradation of 3-deoxyglucosone and the color formation
of the formed melanoidins were determined. In addition, the reaction
mixture was analyzed with high-resolution mass spectrometry and a
Kendrick analysis was applied. Oligomers consisting of up to four
molecules of 3-deoxyglucosone and three amino acids and their respective
dehydration products with furanoidic structure were detected. The
melanoidin structure of C–C linked monomeric units postulated
by Kroh et al. could be confirmed.
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