Why does mochi puff up when baked?
Mochi is made from glutinous rice and is mainly composed of starch. When the glutinous rice cake is baked, the starch absorbs the water in the glutinous rice cake, making it sticky and soft.
This then stretches and becomes just like rubber.
The water in the glutinous rice cake becomes water vapor when it is heated by fire. This steam makes the glutinous rice cake swell up like a balloon.
