# Gluten-Free Sourdough Based on Quinoa and Sorghum: Characterization and Applications in Breadmaking
## 3 Results
### Sourdough Properties
#### 3.3.2 Effect of Sourdough Addition on Thermo-Mechanical Properties of Dough  
The thermo-mechanical properties of dough prepared with various GF flour blends and supplemented with 20% sourdough are presented in Figures 2-4. Analyzing the Mixolab parameters presented in Tables 5-8, one can observe that the addition of sourdough to the GF dough samples caused important modifications to the thermo-mechanical properties including protein weakening, starch gelatinization and starch retrogradation. The WA values, decided when studying the effect of sorghum flour addition on the thermo-mechanical properties of quinoa flour, were selected for testing the influence of sourdough addition to the corresponding GF dough sample. Under these conditions, the C1 values registered for the sourdough-based samples were 1.10 \(\pm\) 0.05 Nm, with an exception concerning the Q100 CS2 sample, in which case C1 was 1.16 Nm (Table 5). [PERSON] and [PERSON] [29] observed a slight increase in WA needed to obtain the C1 of 1.1 Nm in the case of the samples with sourdough addition, compared to the sample without sourdough addition. The sourdough addition resulted in a decrease in Q100- and Q75-based dough stability (S) with respect to the samples with no sourdough addition. On the other hand, the stability increased in the case of the Q50-based samples supplemented with sourdough (Table 5), in agreement with the trend reported by [PERSON] and [PERSON] [29] regarding the stability of the wheat flour dough which increased upon sourdough. In addition, the S8 of the Q75- and Q50-based doughs increased significantly (\(p<0.05\)) upon sourdough addition, with respect to the corresponding samples with no sourdough (Table 5). In the case of the whole quinoa flour doughs, the addition of the spontaneously and SC1 fermented sourdough resulted in no important modification, but a slight decrease in the S8 value was noticed for Q100 SC2 (Table 5). The addition of sourdough resulted in the improvement of the elastic properties of the dough with the highest levels of sorghum flour. The amplitude of the Q100- and Q75-based dough improved significantly (\(p<0.05\)) upon sourdough addition (Table 5). [PERSON] et al. [60] reported lower values for the \(\delta\) angle parameter, which shows the viscoelastic properties of dough prepared with millet flour and sourdough fermented with different strains of lactic acid bacteria, compared to those obtained with yeasts. The authors assigned these results to the improvement of the elastic properties of the dough, which creates the premises to obtain high-quality baking products. Figure 3: The Mixolab curves for the dough samples prepared with quinoa flour (Q100) and quinoa flour substituted with 25 (Q75) and 50% (Q50) sorghum flour and 20% sourdough fermented with a starter culture (SC1). Figure 2: The Mixolab curves for the dough samples prepared with quinoa flour (Q100) and quinoa flour substituted with 25 (Q75) or 50% (Q50) sorghum flour and 20% spontaneously fermented sourdough (C). The sourdough addition resulted in no decrease in the minimum C2 torque, but the values were recorded at higher temperatures and after a longer mixing time with respect to the corresponding GF samples without sourdough addition. The only exception concerns the Q50 SC2 sample, in which case the C2 was registered at a significantly lower temperature (Table 6). The increase in the dough stability after 8 min, the delay in recording the C2 values and the TC2 increase in the case of the dough samples with a higher percentage of quinoa flour and sourdough might be due to the changes in the ratio between soluble and insoluble fibers. [PERSON] et al. [32] investigated the sourdough from quinoa flour and reported an increase in the soluble fiber content simultaneously with a decrease of 35% of the insoluble fiber content, compared to the dough prepared from quinoa flour without sourdough. On the other hand, higher (C1\(-\)C2) values were noticed for the dough samples with higher percentages of quinoa flour and sourdough (Table 6).