Baking Cakes at High Altitudes
High altitude (over 3,000 feet) has less air pressure and drier air. These conditions affect baked goods. The lower air pressure allows the gases created by the leavening agent to expand more quickly and causes liquids to evaporate and boil at lower temperatures. The drier air also dries out the flour.
For cakes, this means that there might be excessive rising from the gases produced by the leavening. This could cause the texture to be coarse or the cake to call before the structure is set by baking. Faster evaporation of the liquid, due to lower boiling point, would reduce the amount of liquid and increase the concentration of sugar. This higher sugar concentration may also weaken the structure of the cake.
Some measures to take for butter cakes are to increase the oven temperature 15° to 25°, which allows cakes to set faster and prevent falling. Fill baking pans half full not two-thirds full, since cakes rise higher. Reduce the leavener and the sugar and increase the liquid. Here are some general guidelines for adjusting ingredients for butter cakes.
For foam cakes, only beat the egg whites until soft peaks form. To strengthen the structure of the cake, decrease the amount of sugar by a tablespoon of two and increase the amount of flour or egg component of the cake a little. Increasing the oven temperature by 15° to 25° will also help set the cake structure sooner.