# Gluten-Free Sourdough Based on Quinoa and Sorghum: Characterization and Applications in Breadmaking
## 3 Results
### Sourdough Properties  
At the end of 20 h of sourdough fermentation at 30 \({}^{\circ}\)C, the number of lactic acid bacteria was evaluated to be between 1.45 \(\pm\) 0.04 \(\times\) 10\({}^{8}\) for Q50 SC2 and 1.16 \(\pm\) 0.04 \(\times\) 10\({}^{9}\) in the case of the Q75 SC1 sample. The increase in lactic acid bacteria concentration was 2-3 log CFU-g\({}^{-1}\), regardless of the ratio between quinoa and sorghum flours. The bacteria from both starter cultures (SC1 and SC2) were able to adapt and grow in the GF flour-based media due to their capacity to degrade and metabolize the carbohydrates existing in the quinoa and sorghum flours. The highest bacterial counts were registered in the case of the G75 (Table 2), suggesting that, in lower quantities, the compounds from the sorghum flour stimulated the bacterial cell growth. Our results are in agreement with those of [PERSON] et al. [32] who reported the density of lactic acid bacteria of 9.3-9.7 log CFU-g\({}^{-1}\) for the quinoa sourdough. Similarly, [PERSON] et al. [33] reported that after the fermentation of quinoa-water media inoculated with 0.2% from the overnight monoculture (which was at 1.3-2.7 \(\times\) 10\({}^{9}\) CFU/mL), the concentration of _L. brevis_ increases to \((8.05\pm 0.1)\times 10^{9}\) CFU/g while _L. acidophilus_ reached (3.2 \(\pm\) 0.1) \(\times\) 10\({}^{10}\) CFU/g, respectively [33]. Moreover, it was stated that the lactic acid bacteria can enhance their fitness by switching from fermentation to respiration metabolism, resulting in a consistent biomass yield and long-term survivability [34; 35] under specific growth conditions, such as the presence of oxygen or specific growth-promoting factors. Regarding the control sourdoughs (C), the growth of the native microbial flora from the flours used for preparing the spontaneously fermented samples was not supported on the MRS media (Table 2). Indeed, [PERSON] et al. [36] compared different available cultivation media, including MRS, used for lactic acid bacteria enumeration and reported that the efficiency in providing quantitative information on the complex sourdough ecosystem is limited. The metabolic profile of the sourdough samples was determined after 20 h of fermentation at 30 \({}^{\circ}\)C by measuring the pH and quantifying the TTA and the main metabolites produced by homo- and heteroferrantative lactic acid bacteria. Analyzing the results presented in Table 3 one can observe that the use of starter culture for preparing the sourdough resulted in significantly higher values of the TTA compared to the corresponding spontaneously fermented samples (_p_ < 0.05). In particular, for all tested GF flour blends, SC1 allowed us to obtain the highest TTA values, ranging from 9.74 to 11.57 mL NaOH 0.1N/10 g, and the lowest pH values in the 4.408-4.454 range (Table 3). Regardless of the starter culture used for fermentation, the increase in the addition of sorghum flour \begin{table}
\begin{tabular}{c c c} \hline  & **Quinoa Flour** & **Sorghum Flour** \\ \hline Moisture, g/100 g & 11.19 \(\pm\) 0.08 \({}^{\mathrm{b}}\) & 11.71 \(\pm\) 0.04 \({}^{\mathrm{a}}\) \\ Protein, g/100 g d.w. & 15.83 \(\pm\) 0.09 \({}^{\mathrm{a}}\) & 9.50 \(\pm\) 0.04 \({}^{\mathrm{b}}\) \\ Fats, g/100 g d.w. & 6.58 \(\pm\) 0.13 \({}^{\mathrm{a}}\) & 3.38 \(\pm\) 0.05 \({}^{\mathrm{b}}\) \\ Fibers, g/100 g d.w. & 6.18 \(\pm\) 0.08 \({}^{\mathrm{b}}\) & 7.19 \(\pm\) 0.28 \({}^{\mathrm{a}}\) \\ Ash, g/100 g d.w. & 2.29 \(\pm\) 0.08 \({}^{\mathrm{a}}\) & 1.89 \(\pm\) 0.10 \({}^{\mathrm{b}}\) \\ \hline \end{tabular} On a line, the average values accompanied by different lowercase letters (a,b) are significantly different (_p_ < 0.05), based on the Tukey test.  
\end{table} 
Table 1: Proximate composition of quinoa and sorghum flours.