In this experiment, discover how gelatin, a tiny molecule, can have a huge impact on food’s texture.
Make a prediction: What do you think will happen when you combine gelatin with hot water, room-temperature water, and ice water?
Use masking tape and marker to label 1 small bowl “Room Temperature,” second small bowl “Hot,” and third small bowl “Cold.” Add 1 teaspoon gelatin to each bowl.
Add ¼ cup (2 ounces) room-temperature water to bowl labeled “Room Temperature.” Use spoon to stir gelatin and water until well combined.
Add ¼ cup (2 ounces) room-temperature water to bowl labeled “Hot.” Use clean spoon to stir gelatin and water until combined. Heat gelatin mixture in microwave until steaming, 30 to 60 seconds. Use oven mitts to remove bowl from microwave and let cool slightly. Use spoon to stir mixture until well combined.
Measure ¼ cup (2 ounces) ice water following photo, below. Add ice water to bowl labeled “Cold.” Use clean spoon to stir gelatin and ice water until well combined.
Observe your results: Look closely at 3 gelatin mixtures and use spoon to stir each mixture. What do you notice? How do the mixtures look similar or different?
Remove bowls from refrigerator and observe your 3 gelatin mixtures again. Use spoon to stir and scoop each mixture, making sure to scrape along bottom of each bowl. How have the mixtures changed during their time in the refrigerator? Do any of the bowls look like a dessert you’ve seen before? Which one(s)?
(Don’t read until you’ve completed the experiment!) When we conducted this experiment in the Recipe Lab, the gelatin mixed with hot water set into a smooth, shiny, clear solid. The gelatin mixed with room-temperature water had an opaque, solid layer on the bottom of the bowl and liquid on the top of the bowl. And the gelatin mixed with ice water never fully solidified—it stayed a chunky liquid.
Gelatin is a kind of protein that’s made up of long, thin molecules. But what gives gelatin its ability to turn liquids into smooth, clear solids, such as Jell-O? First, gelatin is a water magnet—it absorbs water really easily. Second, when gelatin is warm, it’s a liquid, and when it’s cold, it’s a solid called a “gel” (get it?).
When you mix gelatin with a cool liquid, the liquid makes its way into each teeny-tiny granule of gelatin, hydrating it. (This is called “blooming” the gelatin.) At this point, the gelatin mixture looks opaque, meaning that you can’t see through it. Just adding water isn’t enough to make the gelatin dissolve in the liquid. You need to add heat, too.
Heating the mixture dissolves the gelatin in the water, forming a smooth, transparent, pourable liquid. When gelatin is mixed with a hot liquid, its molecules move around a lot—the liquid stays liquid. As the temperature gets colder, the gelatin molecules slow down and start to get tangled, kind of like the cord of your headphones when they’re in your pocket. Eventually, the gelatin molecules get so tangled that they trap the liquid inside. The liquid can’t move around or flow: It becomes a solid.