My daughter was recently pursuing a Girl Scout badge and the project she decided on was to learn how to make bubble tea at home. If you’re not familiar, bubble tea is basically iced tea with little pearls or “bubbles” in it. They can either be a tapioca pearl or a fruit flavored, juicy pearl. She chose the latter, they add a fun snap and burst of complementary flavor to the drink.
We set out to find out how to make these pearls, which turned out to be a rather interesting chemical process and a popular item in “Molecular Gastronomy”. The process is referred to as “spherification” and involves a reaction between Sodium Alginate, which is a seaweed extract, and Calcium Chloride, which is commonly found as pickle juice. When these 2 solutions meet polymerization occurs at the interface between them. When drops of the Sodium Alginate solution are dropped into the Calcium Chloride bath, you get round(ish) pearls with a firm outer shell and a liquid center.
We found many references that turned out to be pretty complex and varied, so we wanted to document our end result in a simple way. The main document we drew from is this one from molecularrecipes.com. The process illustrated here is “Basic Spherification” and is specifically tailored to flavorings with a watery consistency.
You’ll need to gather a few ingredients and items:
- Sodium Alginate
- Calcium Chloride (both are available here)
- Flavoring (we used KoolAid powder) and sugar if needed
- A kitchen or other high precision scale (.1+ gram precision)
- A perforated spoon
- A blender or immersion blender
- An eye dropper or large syringe
- Some bowls and measuring cups
- Any sort of iced tea
The first step is making the flavored liquid. You’ll need to mix your KoolAid, sugar, and water (we used half the directed water for more concentrated flavor) and then add enough Sodium Alginate to make a .5% solution. That is, for every 100g of flavored liquid, you’ll add .5g of Sodium Alginate. In our case we mixed one cup of the prepared KoolAid and 1.2g of Sodium Alginate. This needs to be mixed thoroughly so a blender comes in handy here. Transfer to a cup or bowl and let this sit in the fridge for an hour to dissipate the air bubbles.
The next step is making the Calcium Chloride bath. This is much simpler as the Calcium Chloride is very happy to dissolve in the water. You need the same .5% solution, but will want more of the final solution. We used 4 cups of water and 4.8g of Calcium Chloride. Mix this up with a spoon or whisk until it’s dissolved. You’ll also want to have another bowl of plain water to rinse the bubbles and stop the polymerization.
Finally, you’ll make the bubbles. Using your dropper, drip the flavored liquid into the Calcium Chloride bath. Be gentle and try to space them out. You’ll have to experiment with various pressures and heights to get the best spheres. You can also try different tools and methods to drip the liquid into the bath. You can even make worms! Let the bubbles sit in the bath for about a minute while gently stirring to keep them moving and to avoid flattening.
After a minute, use the perforated spoon to move the bubbles to the water bath. After a rinse in the water, just drop them in your tea and enjoy!
Here’s a closeup of the actual process:
We hope this will help anyone who wants to try making their own. There are many more factors that are discussed in the Molecular Recipes link above, so if you want to try different liquids or processes, check that out. Good Luck!