Potato starch and normal maize starch were gifts from AVEBE and Cargill, respectively. Starch with 16% water (wet basis) was prepared either by dehydration at ambient temperature or by addition of the calculated amount of distilled water and equilibration for 1 week in a closed container with occasional mixing. The water content was checked from the weight loss of the starch after heating (130 C, 2 h) in a free-ventilating oven. A solution of 0.2621 g/l CaCl2. 2H2O in distilled water served as simulated tap water. Aerosil R972 (Degussa) was used as a flow conditioner