## 3 Results and Discussion
### Viability of Microencapsulated Probiotics In Vitro Digestion Process
In addition, the samples with core-to-wall ratio 1:1 coated by WP, WP:DWP 1:1, and WP:DWP 1:3 as well as the samples with core-to-wall ratio 1:1.5 coated by WP:DWP = 3:1, WP:DWP 1:1, and WP:DWP 1:3 have significantly higher cell numbers than others' ones. Therefore, the physicochemical composition, formulation, and concentration of coating materials need to be taken into consideration when planning to produce probiotic microcapsules with high gastrointestinal juice resistance. Bile salt is the main component of bile juice that is involved in the digestion and absorption process of fat content. In addition, it can dissolve bacterial cell membranes and results in viability loss [17]; thus, the resistance of probiotic bacteria to bile salt environment is an imperative property [13; 19; 38]. Therefore, the viability of lyophilized _L plantarum_ 299v strain with different core-to-wall ratios and wall material types as well as formulations were investigated. Time, core-to-wall ratio, formulation, and the combination of ratio and formulation have a significant effect on the viability during the in vitro SJ digestion process (Figure 7). The cell number of each sample significantly decreased in the first 3 h of incubation, and then did not change. Similar results were reported by [PERSON] & [PERSON], (2017) of _S. boualdii_ after 180 min incubation. A possible explanation for this phenomenon may be explained by adaptation properties of the cells to the bile salt or synthesizing bile salt hydrolase [19; 39]. The core-to-wall ratio is another factor that influences the cell viability in the SGJ experiment. In the case of core-to-wall ratio 1:1 of cell to coating material, the cell numbers were significantly higher than those with core-to-wall ratio 1:1.5. This means the increase in the amount of wall material did not provide any higher protecting effect than core-to-wall 1:1.5. [PERSON] and [PERSON] (2015) found that single or double coating materials can take advantage in the elimination of the influence of bile salt on the probiotic bacteria [9]. In addition, capsules coated with WP, WP:DWP 1:3, WP:DWP 1:1 and WP:DWP 3:1 contained a significantly higher cell number than ones coated by DWP. Although the differences of cell numbers of those four formulations were not significant. Meanwhile, the capsules coated by WP with core-to-wall ratio 1:1 exhibited the lowest cell number reduction at approximately 0.35 Log (CFU/g), whereas the highest reduction of cell number (approximately 1.27 Log value) was obtained in the case of capsules coated  
Figure 7: Viability of lyophilized _L. plantarum_ 299v strain with different core-to-wall ratios and formulations after exposure to SJJ for 6 h at 37 °C. WP: whey protein, DWP: denatured whey protein. Superscript letters indicate significant differences (_p_ < 0.05). by WP:DWP 3:1 at the core-to-wall ratio 1:1.5. In the case of DWP as coating material and the core-to-wall ratio was 1:1.5, a slight increase in viable cells was observed suggesting that DWP may weaken the toxicity of bile on cell membrane damage [19; 40]. Many more studies are needed to construct in the future to use DWP as wall material in the coating and releasing processes in food application. After the SGJ and SJI tests, the samples were stored for 20 weeks. The average cell numbers of samples were 9.34, 9.53, and 7.86 Log (CFU/g), respectively. It reveals that the group of formulation and the ratio had significantly better protecting ability against high acidity but worse protecting properties against high bile salt content. In conclusion, taking advantage of WP and DWP, they are promising materials [10; 40] as inner coating materials to form a double layer [17] with better protecting ability against both high acidity and bile salt.