Science of Baking -- Baking Soda & Baking Powder

Chemical agents, such as baking soda and baking powder, found in many baked goods, function as leavening agents. They help lighten or aerate cakes and quick breads, and they help them rise.

Baking soda, known as sodium bicarbonate (NaHCO3), weighs in on a pH scale as a base. To activate it when baking, it MUST be mixed with an acid  -- this causes it to bubble, releasing carbon dioxide (CO2) that expands and helps baked products rise. In addition, the acid neutralizes the base and gets rid of the bitter taste that would occur if the baking soda was not activated. Common acids found in recipes that call for baking soda: sour milk, sour cream, yogurt, buttermilk, vinegar, lemon juice and other citrus juices, cream of tartar, cocoa (but not Dutch cocoa), chocolate, honey, molasses, maple syrup. brown sugar and fruits.

Baking powder is a chemical compound that contains baking soda, dry acids, and starch or some other filler. Since it contains both an acid and a base (baking soda), it can be activated with a cold liquid. Double-acting baking powder is the type found in American grocery stores; this means it actually contains two acids – one that reacts with cold liquid, another that reacts with the heat of the oven.

If your favorite cake or quick bread recipe is suddenly not working, chances are there might be something happening with the baking soda or baking powder. Perhaps the leavening is old and lost its leavening ability. Follow the suggestions below for checking the effectiveness of both baking soda and baking powder . . .

To test baking soda’s effectiveness — Mix 1/4 teaspoon baking soda with 2 teaspoons vinegar; the mixture should bubble immediately. Actually it has a very long (indefinite) shelf life if stored in an airtight container in a cool, dry place . . . so generally an acid will always activate it.
Baking Soda + Vinegar (an acid) = CO2 (release of carbon dioxide which 
helps baked products rise & also neutralizes the taste of the baking soda)

To test baking powder’s effectiveness — Mix 1 teaspoon of baking powder with 3 to 4 tablespoons of water; the mixture should bubble immediately. Store baking powder in a cool dry place; it should be replaced every 6-12 months.

Baking Powder + water (for this experiment hot water works best as it also simulates the effect of a hot oven) = CO2
And, if you want to substitute one chemical leavening agent for another, see what King Arthur Flour has to say @  -- scroll down to the SUBSTITUTE SECTION.

Or, if you’d like to create your own recipe, King Arthur again has advice on how much baking powder or soda to add @

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