By: Nikki Nies 
In baking, there are 2 categories that ingredients fall into- tougheners/strengtheners and tenderizers/weakeners. Tenderizers include fat, egg yolk, sugar, leaveners and acids. Leaveners are chemical agents that cause batters to rise when baked. Leaveners create enlarge the already present bubbles through the creaming of ingredients.
Specifically, this includes baking soda, baking powder, air and steam. These extend shelf life of finished product. Flour, milk, water, whole eggs and egg whites are tougheners. Milk, juice, water and egg add moisture to butter, flour, starch and milk solids are dry ingredients.
As stated before, baking powder and soda are leavening agents. When both ingredients are used in the same recipe, the baking powder does most of the leavening while the baking soda neutralizes the acid in the recipe, adding tenderness and some leavening. Baking powder is composed of baking soda, one or more acid salts (i.e. cream of tartar or sodium aluminum sulfate) and cornstarch to absorb any moisture. Nowadays, most baking powder is double acting, which means it reacts to liquid and heat in two stages.
The initial reaction takes place when adding baking powder to batter and it is moistened. Either cream of tartar or sodium aluminum sulfate, the acid salts, reacts with the baking soda to produce carbon dioxide gas. The second reaction takes place once the batter is in the oven. The gas cells expand causing the batter to rise.
If there’s too much baking soda added to a cake, the mixture will be alkaline, contain a yellowish hue and a soapy flavor. It is often used in recipes with an acidic ingredient (i.e citrus juice, sour cream, yogurt, vinegar, buttermilk, cocoa, honey, molasses, fruit, maple syrup and/or chocolate). Once added to batter, baking soda reacts and releases carbon dioxide gas. Therefore, it’s important to bake batter immediately.
Use of too much baking powder can cause the end product to be bitter in taste, for the batter to rise rapidly and then collapse and/or the crumb will have a fragile, coarse texture. On the other end of the spectrum, when not enough baking powder is used, a cake can be poor in volume or have a compact crumb.
Photo Credit:Happy Herbivore
Sources:http://www.simplyrecipes.com/the_difference_between_baking_soda_and_baking_powder/
http://chemistry.about.com/cs/foodchemistry/f/blbaking.htm
http://simmerandboil.cookinglight.com/2013/03/26/baking-soda-vs-baking-powder/
http://joythebaker.com/2013/10/baking-101-the-difference-between-baking-soda-and-baking-powder/
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