After living in California, we followed these guidelines when we lived in Colorado for 22 years.
At high altitudes, the air density is lower than at sea level. This causes two challenges for cooking at high altitude. Each or all of these adjustments may be required. Only repeated experiments with each recipe can give the most successful proportions to use. Simply use the guide below to adjust your recipe as needed. Where two amounts appear in the table, the smaller adjustment should be tried first. Then if the cake still needs improvement, the larger adjustment can be used the next time. Following these adjustments is an explanation about high altitude cooking.
Reduce baking powder: For each tsp., decrease 1/8 tsp.
Reduce sugar: For each cup, decrease 0 to 1 Tbsp.
Increase liquid: For each cup, add 1 to 2 Tbsp.
For each cup of flour, increase by 1 tablespoon.
For each teaspoon of baking powder or baking soda, decrease by 1/8-1/4 teaspoon.
For each cup of fat, decrease by 1-2 tablespoons.
For each cup of sugar, decrease by 1-2 tablespoons.
For each cup of liquid, increase by 2-4 tablespoons.
Try increasing baking temperature 15-25 degrees to "set" the batter before cells formed by leavening gas expand too much.
Experiment with different combinations. All adjustments may not be necessary.
At higher elevations, water boils at a LOWER temperature, requiring you to cook longer once you hit boiling (and the time it takes you to prepare your recipe). For example, the water's not as hot in Denver as it is in LA at boiling. This is the reason when cooking in the mountains your hot water can be merely tepid, even though it was boiling. If you are making something that needs to be boiled, the cooking process will take longer at high altitudes than at sea level. At as low as 5,000 feet (1,500 meters), the boiling point of water changes enough to significantly change cooking times. For example, expect rice cooked at 5,000 feet (1,500 meters) to take 25-30 minutes instead of 20-25 minutes of simmering before the water is absorbed and the rice is done.
Baked goods rise faster, requiring a change in the proportion of ingredients used in leavened foods (such as breads and cakes). Sometimes, you may need to adjust the baking temperature in your oven as well, BUT changes in altitude do not affect oven temperatures. Since baking items rise quicker at higher altitudes, you may want to increase the oven temperature. So, at elevations over 3500 feet, the oven temperature for batters and doughs should be 25 degrees Fahrenheit higher than the temperature used at sea level. Proofing time for yeast breads should be reduced.
Baking. For any baked goods that rise (yeast breads, cakes or breads made with baking powder, etc.), it's important to adjust the recipe so that the rapid rise time doesn't make the resulting bread or cake too dry. Yeast breads rise more quickly at high altitudes, so be sure to watch your dough carefully and judge the rise time by the change in the dough's bulk, not by the amount of time it takes. Most cake recipes for sea level need no modification up to the altitude of 3,000 feet. Above that, it is often necessary to adjust recipes slightly. Usually, a decrease in leavening or sugar (or both) and an increase in liquid are needed. Always grease your baking pans thoroughly, as cakes and breads tend to stick more when they are baked at high altitudes.
Air pressure at sea level is roughly 15 pounds per square inch. Things in the air is all pulled to the earth by gravity. For example, when you go up a mile in the atmosphere (5,280 ft.) you have much less air pressing down at you. The same is true for being underwater: the closer to the surface you are, the less pressure you feel in your ears; the deeper you go, the greater the pressure. Any reaction that causes expansion will happen slower the closer you are to sea level, since the air pressure surrounding the reaction is greater. But as you go up in the atmosphere, the surrounding air pressure is less. Therefore expanding processes (like rising bread) would seem to happen faster and maybe more profusely
For Recipes Using Baking Powder don't over beat the eggs. Over beating adds too much air to the bread or cake. Raise the baking temperature slightly; the faster cooking time will keep the recipe from rising too much. Decrease the amount of baking powder slightly; this also prevents the recipe from rising too much.
When all else fails, read the directions! Take a close look to find any instructions about preparing your food at a higher elevation. Usually, there will be a note (in fine print) stating what to add or delete from the recipe.
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