This rheological model adjusts the experimental values reasonably well for the different purees. As shown in table 3 the model gave a very good fit showing in all cases a coefficient R2 higher than 0.84 in the shear rate range applied. The model gives a very good fit for the peach and apple purees realized in 2009, while the fit was little good for the other purees. Besides the Casson model was applied because the yield stress is considered. Yield stress is an important quality control parameter in industrial applications, particularly for comparing the overall characteristics of products made on different production lines. A true value of the yield stress could be beneficial for the optimal design of food-processing systems such as those required during thermal processing [10]. As demonstrated by Steffe and Mizrahi the yield stress value is strongly dependent on the shear rate range, type of model, and shape and size of particles forming the purees [4]. The yield stress increased with soluble solids content. In fact the peach purees, having the highest value of solid content, showed the highest value of yield stress.