"I don't like to be suspicious or talk scandal, but sometimes I think the Jumbles have too much baking powder in them." ~ The Emerald City of Oz by Baum, L. Frank
Baking powder is a mixture of baking soda, corn starch, and a mildly acidic compound such as cream of tartar. In baked goods, baking powder is used as a leavening agent. Leavening agents cause breads and other baked goods to rise.
Baking soda (also known as sodium bicarbonate or bicarbonate of soda) is used in making effervescent salts and beverages, artificial mineral water, pharmaceuticals, and fire extinguishers. In baked goods, baking soda is used in baking powder as a leavening agent. In pharmaceuticals, baking soda is used as an antacid, as a cleanser, and to replenish electrolytes.
BAKING POWDER AS A LEAVENING AGENT
"They were known as chechaquos, and they always wilted at the application of the name. They made their bread with baking-powder. This was the invidious distinction between them and the Sour-doughs, who, forsooth, made their bread from sour-dough because they had no baking-powder." ~ White Fang by Jack London
Leavening agents cause breads and other flour mixtures to rise by releasing carbon dioxide gas which expands. Leavening agents include baking powder and baking soda as well as yeasts and some bacterias, as in sourdoughs.
Quick breads such as muffins, biscuits, cakes and cookies usually use baking powder instead of yeasts.
When dissolved in water, the tartaric acid and baking soda in baking powder emit carbon dioxide gas. This expands and produces bubbles which cause the mixture to rise. Generally, one teaspoon of baking powder is used to raise a one cup of flour, one cup of liquid, and one egg.
Single-acting baking powder produces all of its bubbles when it gets wet. Double-acting baking powder produces bubbles a second time when heated.
Yeasts release carbon dioxide through a process of fermentation, which takes up to two or three hours to produce bubbles. Baking powder produces bubbles instantly.
ALUMINUM IN BAKING POWDER
"I'm sure I haven't forgotten anything this time, Marilla. But do you think it will rise? Just suppose perhaps the baking powder isn't good? I used it out of the new can. And Mrs. Lynde says you can never be sure of getting good baking powder nowadays when everything is so adulterated." ~ Anne of Green Gables by Lucy Maud Montgomery
Some baking powders contains aluminum compounds which can be toxic in high amounts and have been linked to neurological conditions such as Alzheimer disease.