The dielectric properties of salted systems based on different hydrocolloids (native or modified starches, or on iota, lambda, or kappa carrageenan) as models for microwaveable white sauces were studied. Microstructural and rheological properties were also studied to better understand the dielectric behaviour. As expected, salt had a significantly positive effect (p < 0.05) on both dielectric properties. Raising the starch concentration significantly lowered (p < 0.05) the loss factor, whereas increasing the carrageenan did not. None of the hydrocolloids significantly affected the penetration depth. The decrease in the loss factor could be related to a decrease in the free water content which was observed by Cryo-SEM. Free water and salt content seemed to be the major factors to control for microwave heating of hydrocolloid-thickened systems. (C) 2009 Elsevier Ltd. All rights reserved.