What do you suppose my first clue might be?
The mellow filling in the spring-form pan rose much more than usual. I thought nothing of it, because everybody likes a mile-high slice of Cheesecake, right? Well, clue number two was the baking time. The cheesecake requires a very high temperature of 500 degrees for (I believe) 90 minutes. At 30 minutes, the top crust was already golden brown. At 45 minutes, it was black and charred. I removed the cheesecake at this point, primarily because I had trouble seeing it through the smoke in the oven. After cooling the molten monstrosity, inspection showed that the graham cracker crust was slightly overdone, but nowhere near as overcooked as the black helmet my cheesecake was wearing. As the cake continued to cool, the black shell split and cracked and peeled, like paint off an old, weathered house. Using a spatula, I removed the “helmet,” and beneath – The charred cheesecake was beautifully golden brown.
I was able to rescue the charred cheesecake, and my host and other guests exhibited amazing patience and understanding, as fellow transplants to the mountains from Upstate New York. It was delicious.
The question is, what factors change at high altitude? Answer: All of them. Okay, I exaggerate. The big ones are atmospheric pressure, humidity and food chemistry. The result will be highly visible: Blackened cheesecake tops, cakes that sink in the middle, flat cookies, batters and fillings that overflow the griddle or pie pans.
Atmospheric pressure: The Colorado State University Cooperative Extension reports that the pressure per square inch at sea level is 14.7, while at 5,000 feet, it is just 12.3 ppi. At 10,000 feet, it is just 10.2 ppi. For every 500 feet or so, water boils at one degree less than the sea-level standard of 212 degrees Farenheit. The change in pressure causes the following:
- faster action by leavening agents
- faster evaporation of moisture
- faster boiling points for liquids
Humidity: Here in the Rockies of Colorado and points south, we enjoy lots of sunshine and an arid/semi-arid desert climate. Humidity is low. The dryness alters the chemical properties of some ingredients, which may affect your recipes. Flour may be drier, requiring more liquid to achieve sea-level/normal humidity results. I've noticed that pasta is drier and more liquid is necessary for baked pasta dishes. On a positive note, bread mold is slower to develop, although bread must be wrapped to avoid drying out.
Food chemistry: Under the confines of lower pressure and faster evacuation of gases, cellular structure is compromised for many items, especially those containing sugars and fats. Adding an extra egg to baked goods and pastry recipes can help offset the weakened cell walls. Decreasing the amount of flour or leavening while increasing the baking temperature may yield better results. Decreasing cooking and baking times may also help.
It would be helpful if some smart people came up with a formula for all this. They have.
Rules of thumb at 5,000+ feet:
- reduce flour and leavening agents by 1/2
- reduce sugar by 2-1/2 tsp. per cup
- Increase liquid by 3 tsp. per cup or one egg
- Increase baking temperature by 15-25 degrees (except with yeasted breads: reduce by 15-25 degrees)
- While increasing the temperature, decrease the baking time by 20 percent.
- For muffins and cakes, fill pans only 1/3 or 1/2
So what actually happened with my cheesecake? As the liquids evaporated so quickly, it altered the concentrations of sugars and fats. I should have increased the liquids by at least 10%, reduced the sugar by 25 percent and decreased the baking time to about 60 to 70 minutes. I'll report back on the next attempt.
I'll leave you with one of my favorite tweeps, Rise Keller, a.k.a. @VanillaGrrl and her presentation on the subject.