Why do breads and pastries swell?

Baking powder is mainly used for the fermentation of steamed buns, breads and pastries. It is used in our daily life to make the product large, soft and delicious. Baking powder is a food additive containing a variety of substances, the main components of which are sodium bicarbonate (NaHCO3) and tartric acid (C4H6O6), usually a compound of carbonate and solid acid. When carbonates come into contact with water and acid, they break down into several substances. 

Release carbon dioxide (CO2) to soften the product. In this chemical process, it does not create seasonings and therefore does not affect the taste of the product.