# Effect of Citrus Fiber on the Rheological Properties of Dough and Quality of the Gluten-Free Bread
## 3 Results and Discussion  
### Rheological Properties of Dough  
The rheological characteristics of the dough, and especially the evaluation of its viscoelastic properties, enable the quantification of the influence of changes in bread formulation. Gluten-free dough based on starch typically behaves as a weak gel in the region of small deformations [4]. Mechanical spectra, showing a dependence of the storage modulus (G\({}^{\prime}\)) and loss modulus (G\({}^{\prime}\)) on angular frequency (\(\omega\)), are shown in Figure 1a. In all cases, the values of the storage modulus dominated over the values of the loss modulus (G\({}^{\prime}\) > G\({}^{\prime\prime}\)), indicating the viscoelastic character of the dough. The proportion of citrus fiber modified the viscoelastic characteristics of the samples, causing an increase in the values of both modules, with the greatest influence being observed for the highest concentration of fiber. The significant dependence of G\({}^{\prime}\) and G\({}^{\prime\prime}\) modules on angular frequency and their relative changes are confirmed by the values of the phase shift tangent (0.1 < tan \(\delta\) < 1) (Figure 1b), indicating the characteristics of weak gels, which confirms previous observations for gluten-free systems [4; 31]. The share of citrus fiber in the amount of 15-20% significantly decreased the values of tan \(\delta\), indicating a strengthening of the dough structure. In an earlier study conducted by [PERSON] and co-authors [26], a 5.5 g addition of orange pomace to the formulation based on 100 g of rice flour and potato starch also resulted in an increase in stiffer or stronger batter. The parameters of power models describing the changes in the value of storage and loss modules in relation to angular frequency are presented in Table 1. The lowest values of K\({}^{\prime}\) and K\({}^{\prime\prime}\) constants corresponding to the initial values of G\({}^{\prime}\) and G\({}^{\prime\prime}\) modules were found for the control (Table 1). Partial replacement of starch with citrus fiber in the amount of 10% even with simultaneous increase in the amount of added water did not significantly affect the changes in the rheological characteristics of the dough. On the other hand, a higher share of fiber in the recipe (15-20%) resulted in a significant increase in K\({}^{\prime}\) and K\({}^{\prime}\) parameters. (Table 1), confirming at the same time the increase in the share of both elastic and viscous characteristics. A significant decrease in the tangent value of the phase shift angle (Table 1) also indicates a strengthening of dough structure under the influence of 15-20% fiber, which is a component with a high swelling capacity. The presence of citrus fiber had only a slighteffect on the values of n\({}^{\prime}\), which indicates the dependence of the value of the storage modulus on the angular frequency, and only its greatest share caused a significant decrease in the value of this parameter (Table 1). On the other hand, the values of the n\({}^{\prime}\) parameter increased significantly with the amount of fiber in the system (Table 1), indicating an increase in the dependence of the G\({}^{\prime}\) module, exhibiting the viscous character of the system, on angular frequency. Figure 1: Mechanical spectra (**a**) and tangent of shift angle (tan \(\delta\) = G\({}^{\prime\prime}\)/G\({}^{\prime}\)) (**b**) of control gluten-free dough and samples with citrus fiber, G\({}^{\prime}\)—filled symbols, G\({}^{\prime\prime}\)—empty symbols. The creep and recovery curves of control dough and samples with an increasing share of citrus fiber are shown in Figure 2. The control sample was most susceptible to the applied stress. With an increasing proportion of citrus fiber in the bread recipe, the susceptibility of the dough to the applied stress was significantly reduced.