Non-enzymatic browning kinetics analysed through water-solids interactions and water mobility in dehydrated potato

Non-enzymatic browning (NEB) development was studied in dehydrated potato at 70°C. It was related to the macroscopic and molecular properties and to water-solid interactions over a wide range of water activities. Time resolved (1)H NMR, thermal transitions and water sorption isotherms were evaluated. Although non-enzymatic browning could be detected in the glassy state; colour development was higher in the supercooled state. The reaction rate increased up to a water content of 26g/100g of solids (aw=0.84) and then decreased at higher water contents, concomitantly with the increase of water proton mobility. The joint analyses of NEB kinetics, water sorption isotherm and proton relaxation behaviour made it evident that the point at which the reaction rate decreased, after a maximum value, could be related to the appearance of highly mobile water. The results obtained in this work indicate that the prediction of chemical reaction kinetics can be performed through the integrated analysis of water sorption, water and solids mobility and the physical state of the matrix.