Why are marshmallows sticky?

Marshmallows are sticky because they are made with gelatin, a protein derived from the collagen found in animal skin, bones, and connective tissue. Gelatin is responsible for the marshmallow's unique soft, chewy texture and its ability to hold its shape. When gelatin is mixed with water and heated, it forms a gel as the protein molecules cross-link and trap water molecules within their network. This gel structure gives marshmallows their characteristic sticky consistency and prevents them from melting at room temperature.

Additional factors that contribute to the stickiness of marshmallows include their high sugar content and their tendency to absorb moisture from the air. Sugar acts as a humectant, which means it has the ability to attract and retain water, further enhancing the stickiness of marshmallows. Additionally, the surface of marshmallows is often coated with a thin layer of corn starch or another starch to prevent them from sticking to themselves or to other surfaces, but this coating can also contribute to their overall stickiness.