## 3 Results and Discussion
### Viability of Microencapsulated Probiotics during Storage  
Viability during the manufacturing or storage is also a fundamental standard for the use of probioticic products. Many researchers have demonstrated that microencapsulated probiotics samples have significantly higher cell density than those samples without microencapsulation [19; 22; 35; 36]. Specifically, the membrane lipid oxidation is the main reason that caused the viability loss [9], thus protecting ability or forming ability of coating materials, temperature, water activity, oxygen content, etc. are the main factors during storage. The effectiveness of ratio and formulation on the storage stability of microencapsulated _L. plantarum_ 299v were investigated. The storage was done at 4 \({}^{\circ}\)C and 25 \({}^{\circ}\)C for 70 days and results are demonstrated in Figure 5. In the case of storage at 4 \({}^{\circ}\)C with core-to-wall ratio 1:1, the sample coated by WP:DWP 3:1 has significantly higher cell number loss rate than the other samples. The cell number decreased gradually in the first two weeks, then it remained constant till the 6 th week. After that the cell number started decreasing again. A similar cell losing pattern was found on samples coated by WP. In this case, the cell number started decreasing sharply after the 8 th week. This may be due to the stability of the coating materials WP:DWP 3:1 and WP with core-to-wall ratio 1:1. However, the losing dynamic was quite different for samples coated by WP:DWP 1:1, WP:DWP 1:3, and DWP. The cell number of those three samples started decreasing from the beginning of the storage process and after 4 weeks with almost a constant loss rate. In the case of storage at 4 \({}^{\circ}\)C with core-to-wall ratio 1:1.5, samples coated by DWP exhibited significantly higher loss rate in cell number than the other samples. The cell number decreased slowly at the first 4 weeks while then it started decreasing faster. Samples coated by WP:DWP 3:1 have the same losing pattern as samples coated by DWP after storage for 6 weeks. This may be due to the stability of the coating materials DWP and DWP 3:1 with core-to-wall ratio 1:1.5. The cell numbers decreased sharply after storage for 4 and 6 weeks under 4 \({}^{\circ}\)C, respectively. Additionally, samples coated by WP, WP:DWP 1:1, and WP:DWP 1:3 shared the same losing dynamic. Figure 4: Scanning electron microscope (SEM) images of \(L\). _plantarum_ 299v cells under 1000\(\times\) (**A,C,E,G,I,K,M,O,Q,S,U**) and 14,000\(\times\) (**B,D,F,H**),**J,L,N,P,R,T,V**) magnification. (**A,B**) are free cells. (**C,D**) are core-to-wall ratio 1:1, WP; (**E,F**) are core-to-wall ratio 1:1, WP:DWP is 3:1; (**G,H**) are core-to-wall ratio 1:1, WP:DWP 1:1; (**I,J**) are ratio 1:1, WP:DWP 1:3; (**K,L**) are core-to-wall ratio 1:1, DWP; (**M,N**) are core-to-wall ratio 1:1.5, WP; (**O,P**) are core-to-wall ratio 1:1.5, WP:DWP 3:1; (**Q,R**) are ratio core-to-wall 1:1.5, WP:DWP 1:1; (**S,T**) are ratio core-to-wall 1:1.5, WP:DWP 1:3; (**U,V**) are core-to-wall ratio 1:1.5, DWP. WP: whey protein; DWP: denatured whey protein. In the cases of storage at 25 \({}^{\circ}\)C with core-to-wall ratio 1:1 of bacteria to coating material, the cell numbers of samples coated by WP:DWP 3:1 and WP:DWP 1:1 exhibited the same trends, i.e., decreased in the first 4 weeks, then kept constant till the 8 th week, and at the end phase they dropped drastically. Generally, the cell numbers of samples with core-to-wall ratio 1:1 stored at 25 \({}^{\circ}\)C have a higher losing rate than of samples stored at 4 \({}^{\circ}\)C. This may be due to the change of moisture of the microcapsules and thus caused the disruption and deactivation of the cell membrane. The increase of moisture content during storage period may be linked to the absorption of water from the environment [37]. In the case of storage at 25 \({}^{\circ}\)C with core-to-wall ratio 1:1.5, the cell number of samples coated by WP:DWP 1:1 had a significantly lower loss rate than by other formulation.