Molecular Gastronomy

The chemistry behind baking

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How Does High Altitude Affect Baking?

As with any amateur baker hoping to rise in the ranks and finally trade in that Easy-Bake oven for the real thing, one must master the manipulation of temperatures, moisture levels, and precise ingredient measurements, whose slight deviation from ideal could render a cake dry or a brownie crusty (gross), before he/she may be rightfully deemed a skilled baker. A factor that many do not take into account while baking, however, is that of a change in altitude and in turn, in air pressure. Since most recipes are designed for baking at sea level, grasping how changes in altitude affect the baking process is essential to understanding why certain modifications are necessary to counteract such effects and to producing the perfect baked good at a high altitude (>3,000 feet above sea level). Who knows? In 10 years’ time, you could be training to be a mountain cook and thanking me for providing you with your first exposure to the chemistry behind high altitude baking.

In order to facilitate a comprehensive delivery on my part of all the factors that influence the baking process at high altitudes, I will address three significant changes that come hand in hand with a change in altitude and collectively represent the answer to the question posed in the title of this post. For one, water boils at a lower temperature with a rise in altitude.

Elevation    Boiling Point of Water
Sea Level 212 ºF
3,000 ft 206.7 ºF
5,000 ft 203.2 ºF
7,000 ft 199 ºF
10,000 ft 194.7 ºF

Why does going up in elevation result in a lower boiling point? Let’s take a minute to consider prior knowledge. If it is known that atmospheric pressure decreases as altitude increases and that the boiling point of a liquid represents the temperature at which its vapor pressure is equivalent to the atmospheric pressure, then it may be concluded that at higher altitudes, the vapor pressure of the liquid could level with the atmospheric pressure at a lower temperature. The greater length of time necessary to bake goods at higher altitudes may be attributed to this observation, as the lower temperature impedes the chemical and physical reactions that take place during baking and cooking. Secondly, liquids are more volatile at higher altitudes. If the boiling point (the temperature at which a liquid may vaporize or a gas may condense) of a liquid is lowered at higher elevations as previously mentioned, then it follows that liquids are also more apt to vaporize or have an increased volatility at greater heights. Then, what does this mean for your baked goods? Moisture would leave your baked goods much more readily at a higher altitude, potentially jeopardizing the overall structure of the goods and subduing the flavor now that there are fewer moisture molecules to carry the aroma. Lastly, air bubbles more readily expand and rise at high altitudes. With a low atmospheric pressure, there is less of a force over the given area counteracting the push of the gases within, resulting in the rapid expansion of leavening gases or bubbles formed from the air, carbon dioxide, and water vapor that rise in products with yeast, baking soda, or baking powder. The next time you go trekking through a mountain and are suddenly overcome by a craving for baked goods, recall these chemical applications to assist you in your baking endeavors!

Check back later for more on the chemistry behind baking! (:

Author: Carrie Xu