Bubble Tea bubbles can be produced using multiple methods, but products on the market are generally produced using the principle called spherification.
Spherification is a type of gelling reaction.
Spherification can be defined as a solution containing calcium lactate or calcium chloride dropped into a sodium alginate solution taking a spherical shape and gelling.
Spherification Mechanism
Spherification is triggered by the movement of calcium ions towards sodium ions, that is, the ions in the dropped liquid moving towards the sodium ions in the solution (from inside to outside).
This ion movement causes the gelling part to take a spherical shape, and while the inside of the structure remains liquid, a shell, membrane, or film layer forms on the outside.
Reverse Spherification Method
The exact opposite of this reaction is also possible. When a solution containing Alginate is dropped into a Calcium solution instead of dropping a solution containing Calcium into an Alginate solution, the spherification reaction still occurs.
However, since the ion movement will be from the surface to the center rather than from the center to the surface, the center of the gel-structured product cannot remain liquid and the entire structure turns into gel form.