Clay Surface Catalysis of Formation of Humic Substances: Potential Role of Maillard Reactions
Javier M. Gonzalez, 2009. "Clay Surface Catalysis of Formation of Humic Substances: Potential Role of Maillard Reactions", Carbon Stabilization by Clays in the Environment: Process and Characterization Methods, David A. Laird, Javiera Cervini Silva, Yona Chen, Claire Chenu, Françoise Elsass, Javier M. Gonzalez, Michael H.B. Hayes, David A. Laird, Alain Plante, Andre J. Simpson, Guixue Song, Jorge Tarcjotzly, Michael L. Thompson, I. Virto, Robert L. Wershaw
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Clay minerals are important from the agricultural, environmental, and industrial point of view because of their chemical and physical properties. Surface acidity of clays is of special interest given that clays catalyze several chemical organic reactions. In natural systems, research has suggested that clays play important roles in the formation of soil organic matter; however, the mechanisms of formation and the roles of clays are poorly understood and/or often controversial. Although, several different pathways of secondary synthesis leading to the formation of humic substances have been proposed, none are universally accepted (Stevenson, 1982). The Maillard reaction, condensation of reducing sugars and amino acids, is one of the proposed pathways for formation of humic substances that has received relatively little attention. The starting materials of the Maillard reaction exist in soils; the questions are whether, and to what extent, clay minerals catalyze the Maillard reaction in soil environments? The objective of this chapter is to compile a synthesis of published research on the formation of soil organic matter with emphasis on the Maillard reaction as a potential pathway for the formation of humic substances and the role of clay minerals as catalysts for Maillard reactions.