Since we're talking about cake and not yeast bread, we'll focus on chemical leavening. The reaction of baking soda or baking powder with the liquids in the batter releases carbon dioxide, which forms air bubbles to help your cakes be light and airy.
As with baking soda, the purpose of baking powder is to create air bubbles that give your baked goods their light, airy texture. There are two types of baking powder: single action and double action. Single action baking powder creates the carbon dioxide bubbles upon contact with moisture, similar to baking soda.
Baking powder and baking soda are both leavening, or rising, agents. However, they contain slightly different ingredients and have different uses. Baking powder and baking soda are common leavening agents for baking. A leavening agent helps baked goods, such as bread and cake, rise by adding gas bubbles.
Baking soda and baking powder are both leaveners made from a chemical called sodium bicarbonate. When sodium bicarbonate is combined with an acid, it produces a gas (carbon dioxide, C02, the same gas we exhale when we're breathing) that lifts cakes, cookies or other baked goodies while they're in the oven.
If you accidentally add baking soda instead of baking powder to baked goods, they won't rise because there is not enough acid. To fix this, add about one tablespoon of white or apple cider vinegar for every half teaspoon of baking soda to the liquids before mixing with the dry ingredients.
Odd soapy taste
Unfortunately, with more baking soda, a lot of it reacts, but some of it (the excess) is left behind, unreacted. This lingering baking soda affects the flavour, which seems "sharper" and too much baking soda might cause your cakes and cookies to taste soapy even.
Baking powder is mixed with the flour. When water is added to this flour to make dough, baking powder undergoes a chemical reaction during which carbon dioxide gas is produced. This carbon dioxide gas gets trapped into the dough and bubbles out which causes the cake to rise making it soft and spongy.
More egg yolks can make a denser cake. Whipped egg whites and folding batter usually results in a fluffy cake. Cake flour also makes it fluffy vs all purpose making it dense. In my experience, cakes with butter are denser than the ones with oil.
Baking Soda
It's used to chemically leaven doughs and batters when it is mixed with an acid. Combining baking soda with an acid produces a chemical reaction that releases carbon dioxide gas which causes the food to expand and become fluffy. Think about light and airy pancakes. That's the baking soda at work.
Therefore, a powder added while baking bread and cakes to make them fluffy and soft is baking powder.
Use 1/4 the amount of baking soda than the amount of baking powder called for in the recipe. Note that per 1/4 tsp of baking soda you need ample amount of acidity which is about 1 cup of buttermilk, 1 cup of brown sugar, 1 teaspoon of lemon juice, or 1 teaspoon of vinegar.
Cakes and pastries are fluffy and light in nature due to the presence of baking soda in it. When baking soda is combined with both an acidic ingredient and a liquid, it becomes activated. Upon activation, Carbon dioxide is produced, which allows baked products to rise and become light and fluffy.
Baking powder and baking soda both help make biscuits and cakes have a nice soft texture. They are both leavening agents. Leavening agents are compounds that create bubbles in the batter, which expand when heated in the oven and create the texture we enjoy to eat!
It is much more powerful than baking powder – you only need about 1/4 teaspoon baking soda per cup of flour to leaven baked goods. Examples of recipes that contain acidic ingredients and call for only baking soda: Vanilla Cupcakes (acidic ingredient: buttermilk)
Milk: Add MILK, not water, when your box mix calls for liquid. The milk adds density, fat and, most importantly, extra flavor to your mix. Egg WHITES: Not adding the yolks to the cake makes the cake fluffy and whiter!
Temperature is the key
To make a cake spongy, the correct temperature should be implemented. The flour and eggs should be at room temperature, and the butter should be warm. Apart from this, the temperature of the oven should be according to the fluffy cake recipe you are following.
Baking powder is a mixture of baking soda NaHCO3 and an edible acid like tartaric acid. Baking powder on heating produces carbon dioxide gas which causes bread or cake to rise making it soft and spongy.
Use of baking soda while baking or making cake, makes the cake taste bitter due to the formation of Sodium carbonate during heating. Hence, to neutralize the formed sodium carbonate and its bitter taste, we use tartaric acid. As an acid tartaric acid neutralizes the base effect of Sodium bicarbonate.
It helps to make these soft and spongy. An aqueous solution of baking soda turns red litmus blue. It is also used in soda acid fire extinguisher.
Too much baking soda will result in a soapy taste with a coarse, open crumb.
Combining the two leavening agents produces a biscuit that is both light and tangy. In baking as in life, it's all about balance. Many recipes need both kinds of reactions to achieve the intended overall balance of flavor and texture, which is why you'll often see both baking soda and baking powder in a recipe.