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


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What is in Cake Mix?

To my fellow bakers out there who cannot even manage to whip up a brownie mix without producing one that resembles a pile of muck, I feel your pain. Our lack of efficiency with an oven, therefore, should justify our clandestine storage of “Betty Crocker” baking mixes near the back of the cupboard. While aggregating the cake mix with the necessary adjuncts (i.e. water/buttermilk, eggs, vegetable oil, etc.) has become routine for us inept bakers, have you ever considered what exactly composes such cake mixes? We are, after all, only familiar with the delectable desserts that our ovens manage to conjure from solely water, eggs, oil, and a mysterious powder mixture, and rarely question the label on the mix box that reads, “Make decadent, bakery-quality cakes in your home oven!”

The components of and chemistry behind packaged cake mix are far from complex. Among the cake mix ingredients include, and are not limited to, flour, sugar, leavening, shortening, emulsifiers, colorings, and flavorings. Below you will find the purpose of and chemistry behind each of these components:

Flour: When combined with water, the mixture forms gluten, a complex protein that allows for the formation and maintenance of gas bubbles, which provides the mix with its malleability.

Sugar: In addition to sweetening baked goods, sugar allows baked treats to maintain their moisture, thus increasing shelf life. Sugar also influences yeast growth; while a sufficient quantity of sugar is necessary to instigate yeast growth, superfluous sugar may render the yeast growth process inactive.


Leavening:  What are the two most common leavening agents? Both baking soda and baking powder are used for cake batters to rise. Simply put, leaveners raise baked goods by expanding the gas bubbles produced by the creaming of ingredients. Baking powder constitutes baking soda, at least one acid salt, and cornstarch to take in all moisture and prevent a reaction from initiating until another liquid is poured in with the batter. When used in cake batter, baking powder reacts in two stages, with the first occurring when the powder is added to moistened batter and an acid salt reacts with the baking soda to form carbon dioxide gas. Once the batter is in the oven, the imposed heat forces the gas bubbles to enlarge and the batter to rise. On the other hand, baking soda, or sodium bicarbonate, leaves most of the leavening to baking powder when both are required in a recipe.



Shortening: Shortenings include the fats or oils of vegetable or animal origin included in baked goods to create a soft, smooth crumb and tenderness. Most shortenings are quite consistent in chemical composition and consist of the following in varying ratios:

  • STEARIN—a naturally-occurring, hard fat of animal origin
  • PALMITIN—a fat, secured from both animal and vegetable sources
  • OLEIN—an oil secured from both animal and vegetable sources
  • LINOLIN—an oil present in cottonseed oil


Emulsifier: Emulsifiers fix the fats and liquids together and contribute to the moistness of baked goods. The most common of emulsifiers is soy lecithin.

Check back later for more about the chemistry of baking! (:

Author: Carrie Xu