BUCHI Encapsulator B-390 - Manual (Page 38)

6 Operation
38 B-390 Operation Manual, Version C
6 .6 Practicing with the Encapsulator, using alginate solution
After getting comfortable with the bead formation controls, perform test runs with non-sterile algi-
nate solutions. Sodium alginate is the most commonly used polymer, but there are others in use
with varying properties. We recommend the low viscosity grade alginate. The alginate concentration
strongly influences the viscosity and this in turn influences the pressure drop in the nozzle. There-
fore, the maximum concentration of the alginate solution is a function of the nozzle diameter (see the
following table).
Table 6-2: Recommended alignate concentration (based on dry weight) for different nozzle diameters
Nozzle diameter
Concentration of low viscosity grade alginate
Working range Recommended concentration
80 to 120 µm 0.75 to 1.4 % 1.1 to 1.2 %
120 to 200 µm 1.0 to 1.6 % 1.3 to 1.4 %
200 to 300 µm 1.2 to 1.8 % 1.5 to 1.6 %
300 to 500 µm 1.5 to 2.5 % 1.8 to 2.0 %
NOTE
Under normal storage conditions the alginate powder contains 10 - 12 % water. Therefore we refer to
the alginate concentration on a dry weight base.
6 .6 .1 Preparation of 1 .5 % Na-alginate solution
1. Take a 400 mL beaker and weigh in 3.3 g Na-alginate powder of low viscosity grade.
2. Add 200 mL of deionized water and mix vigorously with a laboratory mixer for 1 to 2 minutes.
3. Alginate has the tendency to get lumpy. Remove the alginate lumps from the beaker and the mixer
blades with a spatula and mix again for 1 to 2 minutes. If lumps remain in the liquid, repeat mixing.
4. Then let the mixture stand so that the trapped air bubbles will escape from the liquid.
5. If needed, de-gas the mixture under reduced pressure.
6. Dissolution of alginate with a magnetic stirrer takes much more time and should be done over-
night.
NOTE
Alginate solutions will support the growth of microorganisms and are stable for about 2 weeks in a
refrigerator. An indication of microbial contamination is reduction of the mixture’s viscosity. Alginate
solutions can be stored for much longer time, even at room temperature, if sterilized or if preserva-
tives are added, like 0.05 % NaN
3
.