## 3 Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Colour** & **Taste and Flavour** & **Texture** & **Total Score** \\ \hline A1 & 8.00 \(\pm\) 0.75 a & 29.44 \(\pm\) 1.47 c & 35.75 \(\pm\) 1.46 c & 72.34 \(\pm\) 2.42 d \\ A2 & 8.59 \(\pm\) 0.54 a & 32.56 \(\pm\) 1.32 b & 35.65 \(\pm\) 1.25 c & 75.41 \(\pm\) 2.22 c \\ A3 & 8.74 \(\pm\) 0.60 a & 34.56 \(\pm\) 1.25 ab & 44.32 \(\pm\) 1.59 a & 89.80 \(\pm\) 1.76 a \\ A4 & 8.63 \(\pm\) 0.71 a & 34.12 \(\pm\) 1.11 ab & 40.24 \(\pm\) 1.68 b & 82.80 b \\ A5 & 8.60 \(\pm\) 0.57 a & 33.75 \(\pm\) 1.65 ab & 37.38 \(\pm\) 1.82 c & 77.38 \(\pm\) 1.80 c \\ JD & 8.92 \(\pm\) 0.84 a & 35.79 \(\pm\) 1.49 a & 42.31 \(\pm\) 1.64 ab & 90.19 \(\pm\) 1.76 a \\ \hline \hline \end{tabular} Note: Data are represented as mean \(\pm\) SD; figures in the same column followed by different lowercase letters are significantly different from each other (\(p<\) 0.05).  
\end{table} 
Table 3: Sensory evaluation of yogurts produced through fermentation using different ratios of _L. delbrueckii_ subsp. _bulgaricus_ IMAU20312 and _S. thermophilus_ IMAU80809 in starter cultures compared with the commercial starter culture. higher [37]. In our study, the viable cell counts in all samples and the control were in the range of 5.59-5.75 \(\times\) 10\({}^{7}\) CFU/mL at the end of fermentation. The WHC of fermented dairy products is determined by the ability of three-dimensional reticulation of the proteins to retain water [38], probably due to the continuous increase in acid production and WHC of the strain during fermentation. The viscosity of all samples and the control (JD) increased significantly during fermentation, especially in the A3 sample, which reached 615 mPa\(\cdot\)s, which was higher than the control group (590 mPa\(\cdot\)s). Similarly, the WHC of A3 (57%) was higher than the control (47%) and the difference was significant at the end of fermentation. Flavour is one of the most important characteristics of a food product and is an important determinant of consumer acceptability and preference. The sensory properties of dairy products depend to a large extent on the relative balance of flavour compounds in the milk derived from fat, protein or carbohydrates [39]. The distinctive flavour of yogurt is contributed by lactic acid and a complex mixture of aromatic compounds, including volatiles already present in the milk and particular compounds produced during milk fermentation [40]. GC-MS is the most popular technique used for fragrance analysis because of its ability to detect and quantify known compounds, identify unknown compounds and elucidate the chemical properties of molecules [41]. [PERSON] analysed the volatile components of fresh and fermented camels' milk (_L. delbrueckii_ subsp. _bulgaricus_ and _S. thermophilus_) using GC-MS, and showed that lactic acid bacteria played an important role in the fermentation of this milk [41]. In our study, a total of 63 volatile flavour compounds were detected from the samples using GC-MS. To determine how each volatile compound contributed to the flavour profile of all samples, OAV values were calculated (Table 4). Generally, volatile compounds with OAVs \(\geq\) 1 are considered sufficient to contribute to the flavour profile of the yogurt. In our study, some volatile compounds with OAVs \(>\) 1 were found at the end of fermentation, including acetaldehyde (OAV = 2.57), nonanal (OAV = 2.02), 2-nonanone (OAV = 1.99) and formic acid ethenyl ester (OAV = 1.41). Some volatile compounds were present at levels lower than the threshold value (0.1 \(\leq\) OAV \(<\) 1, Table 4), but might still modify the overall flavour of the samples. There were significant differences in the quantities of these volatile compounds (OAVs \(\geq\) 0.1) between the treatments with different ratios of _L. delbrueckii_ subsp. _bulgaricus_ and _S. thermophilus_ in the starter cultures and the control. Thus, the ratio of _L. delbrueckii_ subsp. _bulgaricus_ and _S. thermophilus_ in the starter cultures might be an important factor affecting the aroma of yogurt.