What’s the Science Behind Popping Boba?
- Ryan Wu
- Sep 16
- 2 min read
We’ve all seen popping boba, those little balloons of fruity juice that explode in your mouth with just the slightest push of your tongue. You might’ve seen them in drinks, frozen yogurt, or ice cream.
But have you ever wondered how these fragile little popping bubbles get made?
Here’s the simplified two-step process:
Step 1: Mix fluid food (e.g. mango puree or coke) and sodium alginate.
Sodium Alginate
The fluid food is going to be what’s inside the popping boba. Sodium alginate is a compound that’s extracted from seaweed and made up of two parts (sodium ions and alginic acid … who would’ve guessed!). As you probably already know, sodium is an element on the periodic table.
Alginic acid (or alginate once bound to the sodium ion) on the other hand, is a long carbohydrate. When placed in the fluid food solution, these two parts separate and float freely, with sodium having a positive charge and the alginate portion having a negative charge.
Step 2: Drip or submerge the mixed sodium alginate/food fluid solution into calcium chloride solution.
Calcium Chloride
Like sodium alginate, calcium chloride is a compound that separates into its two parts in a solution, this time being calcium and chloride ions, both elements on the periodic table.
The calcium floats around with a positive charge, and the chloride floats around with a negative charge. When you drop the fluid food/sodium alginate solution into the calcium chloride solution, a new compound is formed in the part where they meet.
This compound is called calcium alginate, where the free floating positive calcium ions from the calcium chloride bond to the free floating negative alginates from the sodium alginate.
Calcium, unlike sodium, can bind to two different alginate molecules, making calcium alginate thicker than sodium alginate. This thick calcium alginate forms a wall around the droplets or spheres of the fluid food/sodium alginate mixture, and since there’s only free floating calcium ions on the surface of the spheres, the interior fluid food/sodium alginate mixture remains liquid. The longer you leave the spheres in the calcium chloride solution, the thicker the wall will become.
Be careful not to leave it in there for too long, unless you want to make chewing boba instead!
Ryan Wu is a rising junior at Hunter College High School in New York, New York. He has participated in the highly selective Science Honors Program at Columbia University since 2024, where he studied university-level topics such as immunology, toxicology, bioengineering, and biotechnology. He currently serves as the layout editor and writer for EATS Food Magazine.
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