# Nutrition, Flavor, and Microbial Communities of Two Traditional Bacterial Douchi from Gansu, China
## 3 Results and Analysis
### Analysis of Nutritional Components of Longnan and Qingyang Douchi
#### 3.1.2 Analysis of FFAs in the Two Types of Douchi  
The results of FFA content determination in Longnan and Qingyang douchi are shown in Table 2. A total of 16 FFAs were detected in Longnan douchi, whereas only 14 were detected in Qingyang douchi. Among them, there were the most types of saturated fatty acids (SFAs) and the highest content of polyunsaturated fatty acids (PUFAs). Longnan and Qingyang douchi contained seven types of SFAs, namely, myristic acid, palmitic acid, heptadecanoic acid, stearic acid, arachidonic acid, behenic acid, and lignoercic acid, accounting for 14.7% and 14.0% of the total FFA content, respectively. Both types of douchi had the highest content of palmitic acid and the next highest content of stearic acid among the SFAs. The two types of douchi contained five monounsaturated fatty acids (MUFAs), namely, _cis_-10-heptadecenoic acid, oleic acid, _cis_-11-eicosenoic acid, erucic acid, and _cis_-15-tetracosenic acid, accounting for 19.2% and 20.1% of the total FFAs content, respectively. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Physicochemical Indicators** & **LN Douchi** & **QY Douchi** \\ \hline Moisture (\%) & 33.96 \(\pm\) 0.44 b  & 37.24 \(\pm\) 0.47 a  \\ Fat (\%) & 2.09 \(\pm\) 0.01 b  & 9.19 \(\pm\) 0.05 a  \\ Amino acid nitrogen (g/100 g) & 1.16 \(\pm\) 0.01 a  & 0.78 \(\pm\) 0.00 b  \\ Salt (g/100 g) & 5.92 \(\pm\) 0.21 a  & 4.19 \(\pm\) 0.13 b  \\ Total acid (g/100 g) & 1.98 \(\pm\) 0.02 a  & 2.04 \(\pm\) 0.02 a  \\ Protein (g/100 g) & 34.14 \(\pm\) 0.26 a  & 28.49 \(\pm\) 0.16 b  \\ \hline \hline \end{tabular} Note: Letters indicate [PERSON]’s pairwise differences among different samples (\(p<0.05\)).  
\end{table} 
Table 1: Test results of basic nutritional components in Longnan and Qingyang douchi. Both types of douchi had oleic acid as the highest content among MUFAs. The two types of douchi contained four PUFAs: linoleic acid, linolenic acid, docosadienoic acid, and _cis_-11, 14-eicosadienoic acid, accounting for 66.1% and 65.9% of the total FFA content, respectively. The PUFAs in both types of douchi with the highest content were linoleic acid followed by linolenic acid. The content of palmitic acid, _cis_-10-heptadecenoic acid, and erucic acid in Longnan douchi was significantly higher than in Qingyang douche (\(p\) < 0.05), which were 10.6%, 33.3%, and 250.0% higher, respectively. _cis_-15-tetracosenic acid and docosadienoic acid were not detected in Qingyang douchi. The content of arachidonic acid and lignoceric acid in Qingyang douchi was significantly higher than in Longnan douchi (\(p\) < 0.05), which were 38.1% and 83.3% higher, respectively. There was no significant difference in the content of stearic acid, behenic acid, _cis_-11-eicosenoic acid, or _cis_-11, 14-eicosadienoic acid between the two types of douchi (\(p\) > 0.05). The main components of common fermented soybean conditions including proteins, fats, sugars, etc., are degraded by a series of enzymes such as proteases, amylases, cellulases, and lignases provided by microorganisms, producing a variety of metabolites such as fatty acids, amino acids, and organic acids, which contribute to the unique nutrition, flavor, taste, and functionality of douchi [15]. The intake of FFAs in food is closely related to human health. Some studies have found that the intake of foods with appropriate ratios of SFAs and PUFA can reduce the morbidity and mortality of some diseases [16]. It was reported that a PUFA/SFA ratio that is less than 0.45 is unhealthy [17]. The PUFA/SFA values of Longnan and Qingyang douchi were 4.49 and 4.71, respectively, indicating that the ratios of FFAs in the Longnan and Qingyang douchi were reasonable and healthier.