## 3 Results and Discussion
### Viability Rate of Lacticaseibacillus rhamnus After Spray Drying and During Powder Storage
After 4 weeks of storage of the powders at room temperature (with 30% oil added in a ratio to the dry weight of the solution), viability in all samples was similar to the controls of 2-3.3% (except for the borage oil) (Figure 1D). When the powders were stored the highest decrease of viable bacteria was observed for powders with 20% hemp oil stored at 20 \({}^{\circ}\)C from approx. 60% after 1 week to approx. 7.5% after 2 weeks (Figure 1B). Powders with 20% wt. added cedar tree oil and nigella oil stored for 4 weeks were characterized by a similar degree of bacterial viability at both refrigeration and room temperature conditions (Figure 1A or Figure 1B). In the case of storage of the powder with the addition of 30% of cedar tree oil, a significant decrease in LGG viability was observed both during storage at 4 \({}^{\circ}\)C and 20 \({}^{\circ}\)C, with slight differences in viability during 4 weeks of storage at both temperatures. For powder with 30% nigella oil at both storage temperatures, the highest decrease in the percentage of viable bacteria was observed after 1 week, while with the addition of milk thistle oil after 4 weeks (Figure 1C or Figure 1D). These results show that bacterial survival after storage of the powders for 4 weeks with each oil (irrespective of its concentration and storage temperature) was significantly different from the reference sample (\(p<0.05\)) (Figure 1A-D). [PERSON] et al. [38] spray-dried three lactobacilli isolates (LB1, S64, and K67) in 10% w/v sodium caseinate (NaCas) as a control, in 10% w/v NaCas in the presence of either low melting point fat (LMF) or vegetable oil. Among the LB1 isolate samples containing vegetable oil as the core material, viability after the spray drying process was almost the same (about 16%), not significantly different compared to the control sample (\(p<0.05\)). In contrast, the addition of a low melting fat gradually increased the viability of LB1 from 16% to 63% as the LMF to wall ratio increased from 0.25 to 1.00 [38]. [PERSON] et al. [39] observed, that the bacterial viability lasts longest at low temperatures when spray-dried _Lbs. rhamnus_ in the carrier based on the mixture of whey protein isolate and maltodextrin (WPI:MD), with the addition of sucrose or trehalose (S or T) as protective agents. Three formulations were spray-dried: WPI:MD 1:2, WPI:MD:S 1:1, and WPI:MD:T 1:1:1. They observed a decrease in cell viability (-Log N/N0) of _Lbs. rhamnus_, relative to the initial count, in probiotic systems stored for 3 months at 5 \({}^{\circ}\)C 4.5, 1.4, 1.6 and at 4 \({}^{\circ}\)C 3.9, 1.9, 1.9, respectively, for the following systems WPI:MD, WPI:MD:S and WPI:MD:T [39]. In general, the application of oils in this study results in higher viability. However, no direct relationship between a higher concentration of oils and the increase in the viability rate of _Lbs. rhamnus_ after the spray drying process was observed, both during the spray drying and storage (Figure 1A-D). Figure 2 shows the viability rate of bacteria after spray drying as a function of the type and concentration of oil. When higher concentrations of oils such as cedar tree, forage, milk thistle, and pumpkin were applied, the viability of the bacteria after spray drying increased, while in the case of hemp and nigella oil, a decrease in viability was observed. Moreover, the effect of oil concentrations was relatively high, where one could observe the increase in viability for higher concentrations of cedar tree, milk thistle, and pumpkin oils, whereas in the case of nigella oil there is an opposite relation. Surprisingly in the case of hemp and borage oils, the changes were almost negligible (Figure 2).