Challenge level: 3
Time: 1 hour hands-on, plus 2 hours to overnight refrigeration
Yield: 3/4 cup (175 ml) fruit juice/sodium alginate mixture for making boba or fruit spaghetti
Use technology adapted from scientific research labs to polymerize tasty fruit spaghetti and popping boba.
- 3/4 cup (175 ml) fruit juice, such as mango/orange juice (no added calcium)
- 1/4 teaspoon sodium alginate
- 2 teaspoons calcium chloride
- 4 cups (946 ml) water, plus extra
- 2 large bowls
- Blender, hand blender, or wire whisk
- Medium bowl
- Mixing spoon or whisk
- Slotted spoon
- Squeeze bottle or medium to large syringe
Pour 3/4 cup fruit juice into a medium bowl and refrigerate for 30 minutes. This will help dissolve the alginate in step 2.
Blend or whisk the cold juice and sprinkle the sodium alginate into the agitated liquid. Mix well, trying to minimize bubbles. The liquid may thicken slightly.
Blend sodium alginate into juice.
Put the liquid in the refrigerator and let it sit for 2 hours to overnight, to remove bubbles.
When the alginate mixture is ready, fill a large bowl with water.
Add the calcium chloride to the water and whisk it in until dissolved, creating a calcium chloride bath.
Add calcium chloride to the water.
Fill the syringe or squeeze bottle with the juice/sodium alginate mixture and try to drip the juice into the calcium chloride bath one drop at a time to form popping boba, also called spherified caviar.
Use a syringe or squeeze bottle to make popping boba.
Let the boba sit in the bath for 1-3 minutes and remove them using a slotted spoon.
Fill a bowl with clean water and use it to rinse the boba.
To make fruit spaghetti, squeeze a continuous stream of fruit juice solution into the calcium chloride bath. Let sit until firm and then remove and rinse as before.
Thick juice solution makes great fruit spaghetti.
Taste your creation. Boba and fruit spaghetti can be stored in fruit juice without sodium alginate.
The Science Behind the Food:
Sodium alginate (say it like you say algae!) is a substance found in the cell walls of brown algae, including seaweed and kelp. Its rubbery, gel-like consistency may be important for the flexibility of seaweed, which gets tossed around on ocean waves.
Here on dry land, you can use sodium alginate to make balloon-like blobs and spaghetti-like strands from fruit juice. We can thank scientists for this delicious project, since they discovered that a chemical reaction between sodium alginate and calcium causes sodium alginate to polymerize, forming a gel. In this experiment, the gel forms on the outside of a sodium alginate fruit juice blob, where the chemical reaction is taking place. The inside remains liquid!
Create and Combine:
- Add popping boba to a fruit smoothie or frozen matcha tea.
- Experiment with different juices to see which ones work best for making popping boba and fruit spaghetti.
Safety Tips and Hints:
- You’ll have to order some of the ingredients for this one, and you’ll need a squeeze bottle or syringe, but it’s so much fun that it’s worth it.
- Fruit juice containing too much calcium will solidify immediately when you add the sodium alginate, so it’s a good idea to have a few different juice options on hand.
More from Kitchen Science Lab for Kids:
Reprinted with permission from Kitchen Science Lab for Kids: 52 Mouth-Watering Recipes and the Everyday Science That Makes Them Taste Amazing by Liz Lee Heinecke and published by Quarry Books, 2019.