Baking soda, bicarbonate of soda and baking powder are all leavening agents, which means they are added to baked goods before cooking to produce carbon dioxide and cause them to rise. Some recipes call for baking soda, while others call for baking powder. Which ingredient is used depends on the other ingredients in the recipe. The goal is to produce a tasty product with a pleasing texture.
Baking soda / Bicarbonate of soda
Baking soda and bicarbonate of soda are in fact different names for the same product. When added to a wet mixture this alkali causes air bubbles to expand when cooked, causing it to rise.
Baking soda/bicarbonate of soda needs to be mixed with moisture and an acidic ingredient for the chemical reaction to take place. Because it needs an acid to create the rising quality, it is often used in recipes where there is already an acidic ingredient present, such as vinegar, citrus juice, sour cream, yogurt, molasses, fruits, lemon juice, chocolate, buttermilk or honey.
The reaction begins immediately upon mixing the ingredients, so you need to bake recipes which call for baking soda immediately, or they will not rise.
Baking soda/bicarbonate of soda give a slightly different quality to that of baking powder when used in cooking. It gives a lovely golden colour and makes a very specific texture not achievable with baking powder. It can have a slightly tangy taste which can quite easily become bitter unless countered by the acidity of another ingredient or soapy if too much is used. Baking soda is about four times as strong as baking powder.
Baking powder contains bicarbonate of soda, but comes pre-mixed with the acidic ingredient (usually cream of tartar) for you as well as a drying ingredient (usually starch such as corn flour). Baking powder contains both an acid and a base and has an overall neutral effect in terms of taste. Recipes that call for baking powder often call for other neutral-tasting ingredients and is a common ingredient in cakes and biscuits.
Most baking powder used today is double-acting which means it reacts twice; to liquid and heat in two separate stages. The first reaction takes place when you add the baking powder to the batter and it is moistened and the acid reacts with the baking soda and produces carbon dioxide gas. The second reaction takes place when the batter is placed in the oven and the gas cells expand causing the batter to rise. Because of the two stages, baking of the batter can be delayed for about 15-20 minutes without it losing its leavening power.
Too much baking powder can cause the batter to be bitter tasting. It can also cause the batter to rise rapidly and then collapse. This will result in the air bubbles growing too large and breaking, and the cake having a coarse, fragile crumb with a fallen centre. Too little baking powder results in a tough cake that has poor volume and a compact crumb.
You can make your own baking powder by simply mixing two parts cream of tartar with one part bicarbonate of soda.
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