# Effect of Citrus Fiber on the Rheological Properties of Dough and Quality of the Gluten-Free Bread
## 3 Results and Discussion
### Bread Characteristics  
The basic parameters characterizing the physical properties of control bread and loaves with citrus fiber are summarized in Table 2. The quality of bread after baking could be initially assessed by the volume of its loaves, and in this case the greatest value was determined for control bread. The share of citrus fiber in the recipe significantly reduced the volume of bread. The biggest decrease in volume was recorded when a 10% share of fiber was applied and reached about 20%. Further increases in the fiber share resulted in a smaller decrease in volume, and at a 20% concentration of fiber the volume was no longer affected in relation to the sample with a 15% share. In earlier studies concerning wheat bread [24; 25], and gluten-free bread based on rice flour and potato starch with methylcellulose [27], the addition of citrus-derived preparations, resulted in a decrease in bread volume, although the effect visibly depended on the formulation which was used as a control [28]. The key factor affecting the volume of bread is the ability of the dough structure to retain fermentation gases. The presence of citrus fiber significantly increases the water absorption of the dough, forcing the addition of water to bread formulation. This in turn leads to the dilution of structure-forming gums. As a result, the dough is more compact and less flexible, which may limit its ability to retain fermentation gases. The decrease in the volume of bread could be limited or reversed by increasing the addition of the structure-forming gums. The presence of citrus fiber in the bread recipe visibly affected crumb characteristics (Table 2, Figure 4). An increase in the porosity of bread with fiber was observed in relation to the control sample and it was the greater the more fiber was in the recipe \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Volume (cm\({}^{3}\))** & **Porosity (-)** & **Cell Density (cm\({}^{-2}\))** & **Average Pore Size (mm\({}^{2}\))** \\ \hline Control GFB & 135.8 \(\pm\) 6.7 \({}^{\circ}\) & 0.416 \(\pm\) 0.009 \({}^{\mathrm{a}}\) & 49.4 \(\pm\) 2.4 \({}^{\mathrm{d}}\) & 0.84 \(\pm\) 0.06 \({}^{\mathrm{a}}\) \\
10\% CF & 110.0 \(\pm\) 6.3 \({}^{\mathrm{b}}\) & 0.431 \(\pm\) 0.007 \({}^{\mathrm{a,b}}\) & 38.1 \(\pm\) 1.4 \({}^{\mathrm{c}}\) & 1.13 \(\pm\) 0.07 \({}^{\mathrm{a,b}}\) \\
15\% CF & 98.3 \(\pm\) 4.1 \({}^{\mathrm{a}}\) & 0.436 \(\pm\) 0.007 \({}^{\mathrm{b}}\) & 32.6 \(\pm\) 2.2 \({}^{\mathrm{b}}\) & 1.37 \(\pm\) 0.15 \({}^{\mathrm{b,c}}\) \\
20\% CF & 95.0 \(\pm\) 5.5 \({}^{\mathrm{a}}\) & 0.455 \(\pm\) 0.018 \({}^{\mathrm{c}}\) & 29.5 \(\pm\) 0.8 \({}^{\mathrm{a}}\) & 1.56 \(\pm\) 0.37 \({}^{\mathrm{c}}\) \\ \hline \hline \end{tabular}  
Mean value of four replications \(\pm\) standard deviation. Mean values signed the same letters in particular rows are not significantly different at 0.05 level of confidence.  
\end{table} 
Table 2: Bread volume and digital image analysis parameters of control gluten-free dough and samples with citrus fiber (CF) addition. Figure 3: Viscosity (b) curves of control gluten-free dough and samples with citrus fiber. (Table 2). In parallel to the increase in porosity, the average pore size increased while cell density decreased (Table 2). Similarly, in the study of [PERSON] and co-workers, the number of cells decreased with increasing orange pomace levels [27]. The data presented in Table 2 are confirmed by the photographs of the cross-section of the loaves of the analyzed bread shown in Figure 4. Especially with a higher content of citrus fiber (15%-20%), a decrease in volume in relation to the control sample (Figure 4a) is clearly visible, as well as an increase in porosity and pore size, with a simultaneous decrease in their density per unit area (Figure 4c,d). The changes in crumb characteristics are confirmed by the results concerning the decrease in loaf volume due to the introduction of highly water-absorbent fiber and water into the recipe.