When you bake a cake, your ingredients must work together. Cooking chemist Charlie Boss puts it this way:
If you forget the eggs, the cake crumbles; forget the baking soda and the cake collapses. The development of a new recipe isn’t complete until all its ingredients are ratioed correctly and they combine in harmony. That’s why cooking in high elevations is such a confusing problem: air pressure is a vital — and usually unmentioned — component of every recipe.
We've discussed how eggs take longer to boil at higher elevations than at sea level. We learned that low air pressure doesn’t restrict water molecules the way that high air pressure does, and that this lower restriction leads to a lower boiling temperature. Well, air pressure doesn’t just affect the physical states of matter; it also affects the chemical reactions between molecules.
Cakes, cookies, and other rising pastries commonly contain baking soda or baking powder — leavening agents. Baking soda and powder are made of the same compound, Sodium Bicarbonate (NaHCO3), which when combined with an acid (H+) and activated with heat, produces water, carbon dioxide, and a free Na+ ion
So what does this mean to you? When a leavening agent goes through a chemical reaction, it releases carbon dioxide bubbles. Those bubbles jitter around inside the mixture while the batter sets. The carbon dioxide bubbles act as a shaky yet competent scaffolding to the congealing batter, and if the recipe works as designed, the carbon dioxide doesn’t escape into the atmosphere until after the cake has hardened completely.
So what does this mean to you? When a leavening agent goes through a chemical reaction, it releases carbon dioxide bubbles. Those bubbles jitter around inside the mixture while the batter sets. The carbon dioxide bubbles act as a shaky yet competent scaffolding to the congealing batter, and if the recipe works as designed, the carbon dioxide doesn’t escape into the atmosphere until after the cake has hardened completely.
In higher elevations, though, the carbon dioxide is more excited, more relatively powerful, and it escapes the cake more quickly. The batter doesn’t have the time it needs to set, so it rises with the bubbles, starts hardening, and since the carbon dioxide leaks out before the batter has finished, the cake can’t support itself and it slumps into the cake pan.
Since most Americans (and American cookbook authors) live in low altitude environments, most recipes are written for low altitude cooking. I mean, just look at this list. Of the top 20 cities for food experimentation, only one is located above 600 feet. So if you’re baking in the mountains, you can find resources online that provide recipes tailored specifically to high altitude, low pressure regions.
