The effect of three fat replacers (xanthan gum, Reihan seed gum & Balangu seed gum) and two sweeteners (sucrose and isomalt) on time-dependent rheological properties of low calorie pistachio butter were analyzed using response surface methodology. The steady shear behavior of all samples was shear-thinning (n= 0.156-0.6175) and power law model was fitted the upward and downward curves properly (R2= 0.847- 0.998). Balangu seed gum (0.01-0.04%wt), Reihan seed gum (0.01-0.023%wt), xanthan gum (0.06-0.1%wt), isomalt (0-1%wt) and sucrose (0.25-1%wt) were the levels investigated. A central composite design was used to develop models for the responses. The obtained experimental data were fitted to a second-order polynomial equation and also analyzed by appropriate statistical methods. In most cases, increasing the sweetener level led to a significant decrease in consistency coefficients. However, the effect on the flow behavior index was not significant. The effect of gum concentration on the rheological parameters was not significant (P 0.1), except for formulas prepared using Balangu seed gum. All studied formulas were stable on shelf.

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