## 3 Results and Discussion
### Viability of Microencapsulated Probiotics In Vitro Digestion Process  
The stomach is the main digestion process that can cause the loss of viability of probiotics due to the low pH and pepsin enzyme. The acidity of the stomach is usually approximately pH 2, which is affected by eating time, quality and quantity of diet [17; 19]. The viability of lyophilized \(L\). _plantarum_ 299v strain with different core-to-wall ratios, wall  
Figure 5: Viability loss of lyophilized \(L\). _plantarum_ 299v strain with core-to-wall ratios and different formulations at 4 \({}^{\circ}\)C and 25 \({}^{\circ}\)C. (**A**): 4 \({}^{\circ}\)C, core-to-wall ratio 1:1, (**B**): 4 \({}^{\circ}\)C, core-to-wall ratio 1:1.5; (**C**): 25 \({}^{\circ}\)C, core-to-wall ratio 1:1, (**D**): 25 \({}^{\circ}\)C, core-to-wall ratio 1:1.5. WP: whey protein, DWP: denatured whey protein. material types and their formulations after being exposed to SGJ at 37 \({}^{\circ}\)C for 3 h are shown in Figure 6. Core-to-wall ratios, formulation, and the combination of ratio and formulation have a significant effect on the viability during the in vitro SGJ digestion process. As can be seen from Figure 6, almost all samples except sample with core-to-wall ratio 1:1.5 coated by DWP did not show any significant differences in viable cells during the SGJ experiment. This is due to the collective effect of the acidity stress [9; 13; 38] that caused the death of probiotics as well as may release the probiotics from the microcapsules. Hence, it can be as a protecting ability of the coating materials with these formulations and ratios against pepsin and low pH digestion environment. However, the difference in ratios and formulations may affect the releasing characteristics of the microcapsules, for example, the samples with core-to-wall ratio 1:1 coated by WP increased the release of probiotic from microcapsules after 3 h incubation causing suddenly increase in cell number. Or the samples with core-to-wall ratio 1:1.5 and coated by DWP gradually increased the releasing of probiotic from microcapsules during the 3 h of incubation. The samples with core-to-wall ratio 1:1 have a significantly higher cell number than those with ratio 1:1.5. This may be due to the physical properties of the microcapsules, which means under the same circumstance, the higher the viable cells of the probiotics together with properties of the coating materials can exhibit higher protecting ability against pepsin and low pH digestion environment. Formulations of coating by WP, WP:DWP 1:3, WP:DWP 1:1 and WP:DWP = 3:1 have a significantly higher cell number than samples coated by DWP alone. However, there is an interesting phenomenon of samples with ratio 1:1.5 coated by DWP. It showed an increasing cell number during the simulated digestion process, which may indicate that DWP has good protecting and releasing abilities as well as buffering capacity. According to the research of [PERSON] and co-workers (2020), WP has good buffering capacity that can relieve the digestive stress from gastrointestinal juice and maintain the cell number of the probiotic product. In our study, the buffering capacity of DWP was outstanding, even better than WP. This may explain the reason that in some cases, the cell numbers did not decrease, instead even increase over time of SGJ. Based on our overall results of the lyophilization, storage, and digestion process, it can be stated that probably DWP with core-to-wall ratio 1:1.5 may not good choice, but it is worth doing more research to explore the advantage  
Figure 6: Viability of lyophilized _L. plantarum_ 299v with different core-to-wall ratios and formulations after exposed to SGJ at 37 \({}^{\circ}\)C for 3 h. WP: whey protein, DWP: denatured whey protein. Superscript letters indicate significant differences (\(p<0.05\)) among incubation time for a given microcapsule. of DWP as coating material.