Spectroscopic Study of Effects of Goethite Surfaces on the Simulated Maillard Reaction Forming Humic-like Substances

Progress of the simulated Maillard reaction for 0.1 mol L−1glycine and ribose mixture solution at 80°C for 0—7 days forming humic-like substances in the presence/absence of goethite was examined by ultraviolet-visible (UV-VIS) spectroscopy. 254 nm and 420 nm absorption intensities for the product solutions with goethite increased faster than for those without goethite, indicating enhancement of the reaction progress in the presence of goethite in several days at 80°C. Adsorption onto goethite of reactants of the reaction were directly monitored by attenuated total reflection infrared (ATR-IR) spectroscopy with thin layers of goethite on the ATR crystal (ZnSe). IR spectral changes with time for the reactant solution (0.1 mol L−1 glycine and ribose mixture solution) on the goethite layer suggested fast adsorption within a few hours at room temperature of oxygenated components of glycine onto positively charged goethite surface. In situ heating ATR-IR kinetic measurements of humic-goethite interfaces will be useful for examining mechanisms of surface processes leading to reaction enhancement. [DOI: 10.1380/ejssnt.2018.411]