## 3 Results and Discussion
### Freeze-Dried Powders  
To each juice before freeze-drying, 15% \(v/v\) of maltodextrin DE = 10 was added. Dried beetroot and red bell pepper juices without the addition of a carrier agent were very hygroscopic, and after a few minutes the FD powder's structure collapsed and the glass transition process took place. Obtained after freeze-drying the fermented juices, beetroot powders were characterized by a high dry matter content (84-98%); beetroot powders had a higher total acidity (TA), approximately 3 g lactic acid/100 g, higher lightness (L*) and redness (a*), and lower yellowness/greenness (b*) than in juices (Table 2). For red bell pepper powders, almost the same correlation was observed as for beetroot powders. The smallest differences were observed for the color coefficients a* and b * with respect to the juices (Tables 1 and 2). The higher total acidity of red bell pepper compared to beetroot powders could be related to the concentration of salt in the marinade and lactic acid concentration in the powder. Freeze-drying causes a decrease in microbial survival, but it is less than while spray-drying or convection-drying. The number of lactic acid bacteria in the powders obtained as a result of lyophilization is presented in Table 2. A decrease in approximately one to three cycles of the powders' log number of LAB in relation to juices was observed. The influence of the lactic acid bacteria used and the fermentation method (fermented  
Figure 2: Carotenoids content in juice and its powders; A, B, C, and other letters—different indexes for series mean statistically significant differences for given values at the level of \(p<0.05\). quices or juices obtained as a result of squeezed fermented vegetables) on the LAB number was not observed. Storage conditions for powders from fermented juices obtained by freeze-drying can be predicted on the basis of thermal analysis methods. The differential scanning calorimetry (DSC) method determines the glass transition temperature (Tg) below which materials should be stored. In the powders obtained, the temperatures ranged from 59 to 66 \({}^{\circ}\)C for beetroot and 46 to 61 for red bell pepper (Table 2). The obtained values allow that the obtained powders can be stored at room temperature, as the literature suggests values lower than the Tg by about 20 \({}^{\circ}\)C are safe [45; 46; 47]. Similar values for dried beetroot powders with maltodextrin were obtained by [PERSON] et al. [48] and reached 61 \({}^{\circ}\)C. Those values for powders can be related to the addition of maltodextrin to juices before freeze-drying. The glass transition is related to the molecular weight of the compound and water content in the sample. It was measured that for maltodextrin, the Tg is above 140 \({}^{\circ}\)C, for sucrose 60 \({}^{\circ}\)C, and for glucose 31 \({}^{\circ}\)C [49; 50]. The mixture of 15% MD with vegetable juices that contained approximately 4-7 g/100 g of sugars could result in a decrease in the Tg to the level mentioned in Table 2.  
In addition to the DSC method, thermal analysis predicts changes during storage. The TGA method can show phase transitions or chemical reactions in powders, which can occur when temperature increases. Thermogravimetry shows \"changes in the mass of a substance during heating or cooling as a function of time and temperature\" [51]. In the TGA analysis, specific regions can be selected by using steps in measurement. In the analysis provided in this research, three steps were used: In the first step, the temperature ranged from 30 to 140, the second step was 140-420, and the third step was 420-600 \({}^{\circ}\)C. The first step is associated with the loss of moisture, whereas the second step, above 120 \({}^{\circ}\)C, shows decomposition processes of, e.g., proteins and carbohydrates [52; 53; 54].