What is the effect of heat on a marshmallow?

When heat is applied to a marshmallow, it undergoes several physical and chemical changes:

1. Softening: As the marshmallow is heated, the sugar and gelatin within it begin to melt and soften. This makes the marshmallow more pliable and easier to stretch or deform.

2. Browning: The surface of the marshmallow may start to brown or caramelize due to the Maillard reaction, a chemical reaction between amino acids and reducing sugars that occurs when food is heated. This browning reaction is responsible for the characteristic golden-brown color of toasted marshmallows.

3. Puffing up: The marshmallow expands and puffs up as the air bubbles inside it expand due to the heat. This is because the heat causes the water vapor trapped within the marshmallow to turn into steam, which expands and pushes against the marshmallow's surface.

4. Melting: With continued heating, the marshmallow will eventually reach its melting point and turn into a liquid. The exact melting point of a marshmallow can vary depending on its composition and the specific temperature it is subjected to.

5. Flowing: Once melted, the marshmallow becomes a viscous, flowing liquid that can be stretched, pulled, or poured. This property makes marshmallows a popular ingredient in desserts and confections, such as s'mores and Rice Krispie treats.

6. Crystallization: Upon cooling, the melted marshmallow can undergo a process called crystallization, where the sugar molecules rearrange and form crystals. This can result in the marshmallow becoming firm and grainy, which is why it's important to control the temperature and cooling process to achieve the desired texture.