Summary
Introduction
Do you enjoy getting creative in the kitchen? If so, this activity is for you! Molecular cuisine—taking tools, ingredients, and methods typically used in science and using them in cooking—might sound fancy and complicated, but some techniques are easy to replicate! Get your hands wet, fire up your creativity, and see how rewarding it can be!
Materials
- Unflavored gelatin powder, two 7g packages
- Water or juice, half cup
- Spoon
- Food coloring, red, blue, or green work well
- Vegetable oil, four cups
- Water
- Four tall containers
- Freezer
- Ice cubes
- Saucepan or microwavable cup
- Stove or microwave
- Dropper or syringe
- Slotted spoon that can scoop items out of the tall containers
- Plate
- Measuring cups
- Work area that can get wet
Prep Work
- Pour about two cups of vegetable oil into each of two tall containers. Place one container in the freezer for at least 30 minutes.
- To prepare the gelatin, pour ½ cup liquid (water or juice) into the cup or saucepan. Add two packages of gelatin powder and stir until all the powder is dissolved. Add food coloring so you can easily see the pearls in the water or oil. Heat the liquid on the stove or in the microwave until very hot while stirring occasionally. Let the gelatin cool for five to ten minutes.
- Fill two more tall containers with about two cups of water each. Add ice cubes to one container to cool the water.
Instructions
- Have the dropper or syringe, the four containers—two filled with water and two filled with oil—and the warm gelatin nearby.
In a minute, you will put a few drops of warm gelatin into each container. What do you think will happen?
- Use the dropper/syringe to put a drop of warm gelatin into each of the containers and watch what happens. Repeat this for a total of three drops in each container.
Do you see little pearls form in some liquids and not in others? Does something similar happen each time? Why do you think this happens?
- Let the drops sit for a minute, then see if you can scoop the pearls out with a slotted spoon.
Which liquid allows you to form gelatin pearls? Why do you think this is the case?
- Rinse the pearls with water and try tasting one.
How do your gelatin pearls taste? What is the texture like?
- Use the leftover warm gelatin to make more gelatin pearls. Try to make different size pearls or gelatin spaghetti. Cool the oil that was in the freezer in between batches if needed.
Cleanup
- Pour the cooking oil into a container and bring it to your local recycling center or dispose of with your garbage. Never pour the cooking oil in the sink! It clings to the pipes and solidifies in time, leading to pipe blockages.
- Wash all equipment with water and soap.
What Happened?
Did droplets of warm gelatin form nice pearls in cold oil, while dropping them in water or room temperature oil failed to form pearls? That is expected.
To prepare the gelatin, you spread gelatin particles in the liquid you used for this experiment (water or juice). These particles unravel into long strings when heated. If the gelatin particles are close enough to each other, a gel can form as they can interlace and create a three-dimensional structure that traps liquid as it cools. When warm gelatin is dropped in water, the gelatin particles spread out over all the water and cannot form a three-dimensional structure. However, when warm gelatin is dropped in oil, the gelatin stays together in little spheres. This happens because water and oil do not mix. Water particles shy away from oil, so they clump together in the shape that gives the least possible interaction with oil: a sphere. Within the sphere, the gelatin particles can form a three-dimensional structure.
In addition to the being close enough to each other, the temperature matters. Gelatin needs to cool below a specific temperature to solidify. While cold oil provides the necessary cooling, room temperature oil does not. As a result, you can scoop out nice solid gelatin pearls from the cold oil bath, but not from the room temperature oil bath or water baths.
Digging Deeper
Molecular gastronomy—the science of culinary phenomena—brings scientific procedures, ingredients, and instruments into the kitchen. Part of this field studies the influence that food preparation techniques have on texture and flavor. Spherification of juices, changing a liquid into semisolid pearls, is one example. The most common method uses two chemicals (like sodium alginate and calcium chloride). One chemical is dissolved in the liquid and another in a water bath. When drops of the treated liquid fall into the bath, they form small spheres. The outside of these spheres solidifies as a result of a chemical reaction between the two additives. There you have it: little drops of liquid confined in a thin, solid membrane!
One can also make gel-like spheres using more common ingredients: gelatin and oil. Gelatin is made of the protein collagen, a large fibrous molecule abundant in many animals, including humans. Collagen makes skin, bones, and tendons strong and somewhat elastic. This large protein is partially broken down and further treated to form gelatin. When gelatin is prepared, its proteins unravel as a response to added heat. These long strings interlace while cooling and create a three-dimensional structure that can trap a lot of liquid. If prepared with water, the resulting gel is transparent, colorless, and flavorless. In the kitchen, it is often used for its unique texture.
Ask an Expert
For Further Exploration
- Can you improve the taste of your gelatin pearls? What oil and what liquid would make an awesome combination? Can you also change the texture?
- Watch your gelatin pearls shrink as they dry out. Put them back into water to see them swell up again. Why would this happen?
- Prepare red cabbage juice by cooking red cabbage in plenty of water. Remove the cabbage and use the purple liquid to make red cabbage juice pearls. Discover how these pearls are special by placing them into vinegar and/or a baking soda solution. Can you also explain your observations?
- Look up other spherification methods. Order the chemicals they use or a spherification kit and make juice balls or yogurt ravioli.
Related Resources
Project Ideas
Activities
Links
- Blog Post: Boba Spherification: The Science of Juice-filled Caviar
- Blog Post: You Can Do That with Yogurt?
- Scientific American: What is Jell-O? How does it turn from a liquid to a solid when it cools?
