The effects of alpha-amylase and extrusion on the viscosity and energy density of uji, a spontaneously fermented thin porridge from different combinations of maize, finger millet, sorghum and cassava, were investigated. Fermentation alone was not able to reduce the viscosity of uji, but addition of 0.1-2.1 ml/100 rut alpfia-amylase to the fermented slurry or extrusion of the fermented and dried flour at 150-180degreesC and a screw speed of 200 rpm reduced the viscosity of 20 g/ 100 in] uji from 6000-7000 to 1000-2000 cP, measured at 40degreesC and Lt shear rate of 50 s(-1). The amount of flour required to make uji could thus be increased by a factor of 2.0-2.5 and consequently it was possible to produce uji with acceptable energy densities (0.6-0.8 kcal/g) for child feeding. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.