Why do you need to use lemon juice or sour milk along with baking soda when a cake?

Baking soda is a base, and when it reacts with an acid, it produces carbon dioxide gas. This gas is what causes cakes to rise. Lemon juice and sour milk are both acidic, so they can be used to activate baking soda.

When baking soda is mixed with an acid, the following reaction occurs:

NaHCO3 + H+ → CO2 + H2O + Na+

The carbon dioxide gas that is produced in this reaction is what causes cakes to rise. The water and sodium ions that are also produced in this reaction are harmless and do not affect the taste or texture of the cake.

Lemon juice and sour milk are both common ingredients in baking, and they can be used interchangeably to activate baking soda. However, it is important to note that sour milk is more acidic than lemon juice, so it will produce more carbon dioxide gas. This can result in a cake that is lighter and fluffier.

If you are using sour milk to activate baking soda, be sure to reduce the amount of baking soda that you use. For every 1 cup of sour milk, you should only use 1/2 teaspoon of baking soda. This will help to prevent the cake from becoming too acidic.

Baking soda can also be activated with other acids, such as vinegar or yogurt. However, lemon juice and sour milk are the most common acids used in baking.