## 3 Results and Discussion
### Incubation Time  
Changes in the storage time and temperature of yogurt dry ingredients also influenced the yogurt incubation time to the value of pH 4.6 (Table 7). Storage time statistically increased incubation time, but these values were in a standard time range: 7.2-8.6 h. Only for yogurt dry ingredients stored at 20 \({}^{\circ}\)C for 8 weeks was a sudden increase in incubation time observed--15.6 h.  
Yogurts obtained from the powders stored at lower temperatures needed shorter incubation times. For all bacteria, there was a linear correlation between bacteria counts and incubation time (besides a sample with 15.6 h) (charts are not shown, R\({}^{2}\) > 0.9). Storing the starter culture at 5 \({}^{\circ}\)C between 2 and 8 weeks did not have significant effects (\(p\) > 0.05) on the incubation time required to produce the yogurt (8.1 and 8.4 h, accordingly) (Table 7). The storage time of the starter culture at 5 \({}^{\circ}\)C also did not statistically affect its viability (8.54-8.11 log) (Table 4). These results are consistent with the findings of [PERSON] and [PERSON] [43], who stated that the freeze-dried concentrated starter cultures are stable at 5 \({}^{\circ}\)C without a loss of activity. Furthermore, [PERSON] et al. [44] studied the survival of eight different freeze-dried species of lactic acid bacteria during the storage and found that most cultures could be stored for one year at 5 \({}^{\circ}\)C without any significant loss in viability. However, it is important to point out that the storage stability of freeze-dried starter cultures is intimately related to the types of cryoprotectants added to the initial culture before freeze-drying. The author concluded that the sucrose-based cryoprotectants induced excellent stability under challenging conditions, including storage at high temperatures and exposure to acid and bile [45]. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Firmness** & **Surf.** & **Ultra.** & **Storage Mod.** & **Tan Delta** & **Water** \\  & **(N)** & **Roughness** & **Viscosity** & **at 43.6 \(\mu\)Nm** & **at 43.6 \(\mu\)Nm** & **Activity** \\  & & **R\({}_{\text{q}}\) (nm)** & **(mPas\_gcm\_3)** & **(Pa)** & **(Pa)** & **(Pa)** \\ \hline
**Firmness** & 1 & & & & & \\
**(N)** & 1 & & & & & \\ \hline
**Surf. Roughness R\({}_{\text{q}}\) (nm)** & \(-\)0.96897 & 1 & & & & \\ \hline
**Ultra. viscosity** & 0.981541 & \(-\)0.97781 & 1 & & & \\
**(mPas\_gcm\_3)** & 0.734451 & \(-\)0.84357 & 0.84474 & 1 & & \\
**Storage mod.** & & & & & & \\ at 43.6 \(\mu\)Nm & 0.734451 & \(-\)0.84357 & 0.84474 & 1 & & \\
**Tan delta** & & & & & & \\ at 43.6 \(\mu\)Nm & \(-\)0.36523 & 0.536141 & \(-\)0.52787 & \(-\)0.9 & 1 & \\ \hline
**Water** & & & & & & \\ activity & \(-\)0.97483 & 0.979971 & \(-\)0.99928 & \(-\)0.86402 & 0.55872 & 1 \\ \hline \end{tabular}
\end{table} 
Table 6: Multivariate Pearson coefficients for correlation between all measured properties of yogurt produced from dry ingredients stored at different times and temperatures. The results show (Table 4) that the prolonged storage at high temperatures caused a detrimental effect on the activity of the freeze-dried starter cultures present in the yogurt dry formula. The largest decrease in bacteria count was observed for the samples stored for 8 weeks at 20 \({}^{\circ}\)C, with the highest drop noted for _Bifidobacterium lactis_ (0.85 log). This is consistent with the findings reported by other researchers. [PERSON] et al. [46] studied the survival rates of freeze-dried _Lactococcus_ starter cultures and demonstrated that temperature had a destructive effect on the survival rates.