For the samples containing high fat content, a high g1 value and a low Ea value were observed. Ea represents the activation energy of the flow and it indicates a large effect of temperature on viscosity (Steffe, 1996; Telis-Romero et al., 1999). The highest Ea value was exhibited by the sample containing 15% fat and the Ea values decreased markedly with an increase in fat content (i.e. suspended particles). The explanation is that there was an effect of fat contributing in the change of apparent viscosity. This observation is consistent with the work of Saravacos (1970). They reported that the activation energy of flow decreased significantly when suspended particles were present in the product.