Chemical changes are always characterized by the formation of a new substance. Certain chemical reactions are highly noticeable, but the food chemical changes taking place around us are quite subtle. Some examples of food chemical changes around us are as follows:Baking of a cake: The cake rises and becomes spongy due to the bubbles of carbon dioxide gas trying to escape from the batter after the decomposition of baking soda. Caramelization: In the process of caramelization, sugar decomposes to form a specific taste and aroma. Fermentation: It is the process in which a living organism will convert a carbohydrate, such as starch or sugar into alcohol or an acid. The batter which is used to prepare dosa and idli is often fermented for a long period of time. Even in the case of bread, yeast is added to the dough. The yeast decomposes the starch to form sugars. The sugar then metabolizes to form carbon dioxide and alcohol. It is the carbon dioxide that makes the bread rise. Bacteria ferment the lactose in milk into lactic acid and change it to curd.