Maillard reaction humic substances

Humic substances. Analogous to the reactions described above, humic substances (the polymeric pigments from soil (humus) and marine sediments) can be formed by both enzymatic and non-enzymatic browning. High concentrations of free calcium and phosphate ions and supersaturation with respect to hydroxyapatite can sustain in soil, because adsorption of humic acids to mineral surfaces inhibits crystal growth (Inskeep and Silvertooth, 1988). A similar adsorption to tooth mineral in a caries lesion can be anticipated for polycarboxylic polymers from either the Maillard reaction or enzymatic browning. 

Birnessite (8-Mn02) Investigation of the effect of light on Maillard reaction—condensation of glucose and glycine (measurement of optical density) yields of humic substances EPR and XANES study of change in speciation of Mn FTIR study of solid residues Jokic et al. (2001a)... 

Little is known on the catalysis of the Maillard reaction and especially the integrated polyphenol-Maillard reaction by natural soils and sediments. Further work is warranted on this subject matter to advance our understanding of the role of abiotic catalysis in the formation of humic substances and related C turnover and N transformations in the environment. 

Burdon542 has surveyed the current hypotheses for the structure of humic substances and has concluded that the various products from chemical degradations and NMR data are all consistent with their being mixtures of plant and microbial materials and their microbial degradation products. The examination of soil carbohydrates, proteins, lipids, and aromatics supported this view the presence of colour, fluorescence, ESR signals, mellitic acid, and other features do not contradict it. Regarding the Maillard reaction, some free monosaccharides and the necessary amino species are present in soil, so it may proceed, but only to a small extent it is not a major process. However, in marine environments, the relative abundance of carbohydrates and proteins makes them more probable precursors of humic substances than lignin or polyphenols. 

The chemical degradation of carbohydrates, particularly under acidic conditions, produces reductones, furan derivatives, pyruvaldehyde, and so on, which can condense, either among themselves or with amino compounds (Maillard reactions), to produce dark-colored, amorphous products, similar to humic substances. Pyruvaldehyde, which has been held to be an intermediate in Maillard reactions, has been identified in many soils. Such con-... 

As suggested by the works of Abelson and Hare (1971), Hoering (1973), and Hedges (1976) on synthetic and natural humic acids and humin, the Maillard reaction involving carbohydrates and amino acids is a probable mechanism of formation of lake humic substances. However, the apparently rapid formation of lake humic substances makes us consider that reactions between carbohydrates and proteins in dead phytoplankton or in surface sediments are also probable. 

In conclusion, in the early stage of diagenesis, biochemical compounds and the hydrolyzable part (including biochemical components) of humic substances decrease gradually with depth primarily by degradation and, in part, by Maillard-type reaction (i.e., humification). 

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