A good fluffy pancake will rise almost as if by magic when it hits the griddle. The reason some pancakes fluff up while others aren't much lighter than the plate they sit on comes down to kitchen science. In order to fluff up, a pancake has to have the right balance between the air holes and the structure around those air holes.
Baking Powder Provides the Gas
Baking powder is baking soda combined with a chemical acidifier. When baking soda gets wet, the two parts of baking powder combine, reacting like a vinegar and baking soda combination. Carbon dioxide gas bubbles form throughout the batter. Add a second mild acid -- buttermilk, honey, yogurt, or cocoa -- and even more air bubbles will form.
Protein Provides the Structure
Gas bubbles escape, however, unless trapped within some kind of structure. In pancakes, the gluten in the flour and the protein strands in the eggs provide the structure. If you think of "building" a pancake like building a house, protein strands are the lumber that encloses a room. Overmixing pancake batter does two things: it toughens the gluten of the flour, and it lets the gases escape. For the perfect architecture, mix pancake batter just until all the dry ingredients are wet, leaving a few small lumps. Then let the batter sit in the refrigerator for a few minutes. Doing so keeps the gas in the batter and keeps the walls of the air bubbles tender.
Heat Expands the Gas
When the batter hits the griddle, it fluffs up quickly. Bread makers call this sudden rise on contact with heat "spring." Pancakes spring for two reasons. First, double-acting baking powder is designed to release more gas when it gets hot. Second, heat causes the carbon dioxide bubbles to expand. Think about boiling a pot of water. As the water begins to boil, the lid of the pot begins to rattle with escaping gases. Hot gases take up more room than cool gases. Hot gases trapped by protein walls will expand those walls out. Larger gas cells mean a lighter pancake.
Heat Sets the Protein
For the pancake to stay light, the proteins in the batter must coagulate before the gas breaks through the walls and escapes. Heat causes protein to coagulate. The protein in eggs coagulates at 150 degrees Fahrenheit. Gluten, the protein in flour, coagulates at about 160 degrees. When they coagulate they get firm. The carbon dioxide can break through and escape, but the "room" remains.
References
- "How to Read a French Fry and Other Stories of Intriguing Kitchen Science"; Russ Parsons; 2001
- "Kitchen Science"; Howard Hillman; 1989
- University of California Berkeley: Building a Better Pancake
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