Cooking is an art, but baking is a science. Experienced bakers know that baking powder and baking soda have to be decreased as altitude rises. Eggs have to be beaten less and steps taken to reduce the amount of air introduced into batters as altitude increases, but why is this so?
Baking powder and baking soda are used to make cakes and breads fluffy. Some of us have eaten Matzoh or other unleavened breads. For Jews during Passover, Matzoh is a remembrance of a time when their ancestors fled Egyptian captivity. So quickly did they leave, that the bread was made in a bread machine, unleavened or without yeast because there was no time to let it rise.
Many of us have also eaten sourdough breads based on recipes first formulated with wild yeasts during California’s Gold Rush days. In each of these cases, yeast improves the texture and lightness of the bread by producing carbon dioxide gas that makes the bread rise. The lightly bubbled texture of the bread comes when the gas bubbles through.
Today, many flours are self-rising, that is to say, that baking soda or baking powder replaces the yeast of days yore. A chemical reaction, not a growing organism, does the lifting.
One of the major physical forces involved in baking at high altitudes is known as Boyle’s Law. Boyle’s law describes how gases act under pressure. Gases are light and they rise. What determines whether gases will remain dissolved or dissipate are temperature and pressure.
Lower temperatures reduce the amount of energy in the gases and keep more dissolved, but as temperatures rise, they start to escape. Boiling soup is an example. As you add heat, the smooth surface of your soup suddenly starts to bubble and pop as air rises.
Higher pressures keep gases in solution also. Think of the classic example of a cold soda retrieved from the fridge. As you twist off the cap, carbon dioxide starts bubbling out. Eventually, without the cap to keep it in, all the gas will be lost and the soda will go flat. Or think of yourself on a city bus or train when an amply-proportioned gentleman or lady spills onto your lap. Try as you might to escape, you are going nowhere so long as that person is sitting on you.
We often forget that we live under an ocean of air. At sea level, the air is pressing on us at 14.7 pounds to the square inch, known as one atmosphere. But for scuba divers the pressure may be much more so that their blood fills with dangerous gases that bubble out when they rise. That is why they must rise to the surface slowly to allow the gas to disappear slowly and harmlessly. Otherwise, decompression sickness or “the bends,” results and the diver must be put back under pressure in a barometric chamber or die.
Breads and cakes baked at high altitudes without making adjustments are like a diver brought too quickly to the surface. At high altitudes one is closer to the top of an ocean of air and the pressure is lower than at sea level. Gases dissolved in the dough escape more rapidly than desired and wreck the texture of the baked goods.
Reducing the amount of air by under-beating eggs and reducing the amount of leavening such as baking powder or soda are the most important adjustments that a high altitude cook must make. You will also have to slightly increase moisture at high altitudes as flours tend to dry. Finally, baked goods need a bit more sugar as altitudes increase
Some of this is trial and error, but Pillsbury’s website and the beloved cookbook, “Joy of Cooking, ” by Irma S. Rombauer and Marion Rombauer Becker detail how to make these adjustments and even provide high-altitude recipes.
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