Comparative studies of the hydration of maltodextrins were undertaken by proton, deuterium and oxygen‐17 NMR. The 1H and 2H‐NMR transverse relaxation rates of hydrated maltodextrins were sensitive to both chemical exchange with the solvent and hydrogen bonding involving hydroxyl groups. The short average correlation time of water “bound” to maltodextrins (∼ 47 ps) derived from our 17O‐NMR data shows that water is highly mobile and that maltodextrins–at high moisture contents–contribute little to the stability of food products. The onset of aggregation is monitored by all three nuclei. The mechanism of this aggregation process involves hydrogen bonding in un‐heated polysaccharide mixtures and waxy maize starch samples, and is markedly affected by heating to 60°C. Copyright © 1990, Wiley Blackwell. All rights reserved