Abstract: Rheology properties of wheat flour doughs with different levels of natural inulin were analyzed using rheofermentometer. Inulin addition, fermentation time and yeast inoculum size were investigated as independent variables using one-factor-at-a-time (OFAT) and central composite design (CCD) methods. The response variable was weighted average of bread specific volume, sensory score, hardness and elasticity. The results showed that with the increase of inulin addition, the total amount of CO2 was increased, the maximum expansion height was decreased, and the cavity-forming time of dough was significantly reduced. The retention coefficient of CO2 was increased by 18.0% after substitution of 10% flour by inulin, which was perhaps attributed to a certain amount of oligosaccharides in inulin and the ability to enhance the dough resistance to extension. According to the results of response surface analysis, addition of inulin reduced the hardness but had no significant effect on the springiness, and it slightly increased the specific volume of bread. Bread with the highest weighted average score (94.17) was obtained by addition of 4.43% inulin and 86 min fermentation with 1.08% dry yeast. The estimated values from the regression equation were in agreement well with the experimental data.

Key words: inulin, bread, rheology, response surface optimization, weighed average score