Why do some recipes change at higher altitudes?

My Rice-a-Roni red beans and rice (yummy if you add lots of red-hot sauce and a dash of habenero to make it scorching) says to add more water and increase cooking time if cooking “at high altitudes,” whatever that means.

This is not the first time I’ve come across this instruction. Is there really that much difference between cooking stuff in Michigan and cooking it in Aspen, Colorado? Why?

(This is one of those scientifical things I should have payed better attention to in high school, isn’t it?)

Because air pressure is lower at higher altitudes. In the case of your Rice-a-Roni, what’s important is that water will boil at a lower temperature in Denver than in Baltimore. The rice, noodles and whatever else they’re adding to 'Roni these days will need to cook for a longer period of time, because they are being cooked at a lower temperature. During this longer period of time, more water will boil away, so you need to start with more liquid. Try to make it according to standard directions up on a mountaintop, and you will end up with undercooked 'Roni that’s burned on the bottom.

The lower air pressure also changes how leavening agents react, so any recipe that uses baking soda, baking powder, or yeast will have to be adjusted slightly.

What flodnak said.

When we lived in Los Alamos NM (7000 ft), recipes needed adjusting. Occasionally we would go on hiking/mountain climbing trips and the difference was far more dramatic when you got over 11,000 ft. Your coffee (boiling water poured over instant) would feel warm rather than hot in your mouth; you could almost bathe in boiling water up there!

People who live at such high altitudes use pressure cookers for a lot of things.

The climbers on Mount Everest are typically able to drink down boiling water straight out of the pot because it boils at such a low temperature.

In order for water to evaporate (boil), it must first overcome the pressure exerted against its surface by the column of air resting upon it. This column extends all the way out to space and amounts to some 16-17 pounds per square inch of surface area. At altitudes of more than a mile, the lessening of this pressure causes pronounced changes in the cooking properties of water based recipes.

Ironically, here at nine-tenths of a mile (higher than the 3,000’ threshold usually listed on the package), I find that cooking times seem to be a little bit shorter than listed. Maybe it’s just the brand of pasta I’m buying now.

Some quick facts from my Steam Tables and a handy program I wrote of average atmospheric pressures at different elevations:

Elevation           Pressure, psia         Boiling Point, F
Sea Level           14.70                  212
  1000 ft           14.18                  210
  3000 ft           13.17                  206
  5280 ft           12.30                  202
  7000 ft           11.34                  199
11,000 ft            9.71                  192
14,410 ft            8.52                  185
15,000 ft            8.09                  183
29,028 ft            4.12                  154

Note - 14,410 ft is Pike’s Peak, 29,028 ft is Everest (old measure) Also note the “Boiling Point” listed is the saturation pressure - you will see some boiling activity at a bit lower temperature than that.

Thanks for the correction Anth.

Eeek! I meant to say saturation temperature. :wink: