Some Notes on Baking at Altitude

2020-08-17 09:11:30.000 – Nate Iannuccillo, Weather Observer/Education Specialist


A couple weeks ago, during the first installment of the Observatory’s Science in the Mountains series, I mentioned that I had a sourdough starter that I take with me up and down the mountain each week for home baking action on and off the summit. After the program, someone asked how my sourdough starter behaved at altitude, and this question inspired me to share a few thoughts on baking at altitude.
I first started baking bread while working for the Appalachian Mountain Club’s high mountain huts. After my days in the huts, I continued home baking, eventually stepping into the realm of sourdough, and through a series of events, I went on to work at Old Village Bakery in North Conway before working at the observatory. Old Village Bakery is actually owned and operated by former weather observer Mark Ross-Parent, and I certainly recommend checking it out if you’re in the area!
Working with Mark and friends at the bakery was a blast, we baked delicious breads and pastries, drank too much coffee, and watched many a sunrise together. I also learned a lot about the science of baking, and how relevant the atmospheric conditions are to successful baking projects.
In fact, I actually feel like this is one of the most exciting things about baking; there really is a lot of science going once you start paying attention. In this capacity, I see a lot of parallels between successful baking and the meticulousness required of a weather observer. On any given day, I feel that if I want to produce consistent and quality bread, I have to be diligent in terms of my regard for the variables that help frame this process. Some of these variables we can control with relative ease while others prove more challenging. Responding to different environmental conditions is where the baker’s intuition comes into play, and I’ll try to elaborate on this notion in a bit more detail.
To begin, ingredients are weighed and measured with strict precision, something that I would say becomes habitual and fairly straightforward. The first big variable comes into play when considering the desired dough temperature. The temperature of the dough affects the activity of the microorganisms hard at work in the fermentation process, the yeast and lactic acid bacteria, and in turn will affect how quickly the dough rises as well as the bacterial production of lactic acid. Colder temperatures lead to slower rises and more lactic acid produced in the dough, which gives the bread the sour flavors so sought after in sourdough baking. When I bake sourdough, I generally aim for really low dough temperatures and really lengthy rises, in order to sufficiently cultivate these flavors so that I can get a properly sour sourdough.
Without the presence indoor climate control, the main way for the baker to control dough temperature is to regulate the temperature of the water used when mixing the dough. If I’m expecting a hot day, I might respond by using colder water during the mix in order to offset the additional warming effecting the dough.
Humidity also plays a part in this process. Despite frequently exhibiting high relative humidity readings and spending 60% of the year in the fog, the summit is actually a drier climate than the valley. This makes sense when considering the notion of absolute humidity and the much colder temperatures exhibited on the summit. Essentially, the maximum concentration of water vapor in the air is proportional to temperature, so water condenses at a lower concentration on the summit even though the actual concentration of water vapor might be lower than that of the valley.
So what does this have to do with baking?
The main way this comes into play involves mixing, with potentially drier flour requiring additional water to reach the proper dough hydration. So far, I’ve found this to be true, with most of my summit projects requiring additional water in order to achieve the desired consistency. The other thing to be mindful of is the higher rate of evaporation that is often exhibited on dry days, and I’m careful to avoid letting the exterior of the dough dry out both during handling and proofing.
I should mention that this challenge isn’t unique to the summit; the day to day variations in humidity were conditions that I was frequently responding to even at the bakery. Often times on a dry day, if I left the door open, the exterior of the dough might be liable to dry out in minutes if I wasn’t careful…
The last variable I should mention is the difference in atmospheric pressure, a factor that is much more significant when considering altitude. Granted, atmospheric pressure is in constant flux, but daily pressure fluctuations are relatively minor compared to effects of altitude on pressure readings. To try to provide some sense of scale here, the pressure on the summit at any given time is around 200 millibars lower than sea level pressure, whereas daily pressure fluctuations tend to be in the ballpark of 0 to 5 millibars. Because of this, I tend to think that daily pressure tendencies would be rather negligible when considering their effects on baking.
However, when baking on the summit, the much lower air pressure cannot be ignored. What this amounts to is dough rising faster at higher altitudes, and it makes intuitive sense when you think about how there is actually less atmosphere sitting on top of the dough at high elevations.
In turn, I respond to faster rises by aiming for a colder dough temperature, because like I said earlier, I’m usually trying to cultivate sour flavors. Otherwise, there’s nothing inherently wrong or problematic with bread that’s rising faster as long as you’re aware of the changes that are going on. At the bakery, the bread is kept on a timely proofing schedule, where everything from the initial mix, successive folds, and the final shaping times are recorded in advance of the actual bake. This is an essential component to producing consistent bread, and I would say it works quite well, despite a few shifting variables.
When I bake at home, I am often a bit less meticulous, preferring to bake “by feel”, and I would say my bread usually turns out pretty good despite this approach.
I mention this because it is difficult for me to quantitatively describe high altitude baking when I’m not actually keeping track of all of the variables. Essentially, if dough temperature, air temperature, and humidity are the same, high altitude will lead to a faster rise every time, because the atmospheric pressure is lower at a higher altitude. But of course, these variables are not the same, so the altitude is just one more thing to consider, especially if I’m baking “by feel”. The main thing I hope to highlight is that baking bread incorporates many of the same elements that I’m actively recording and observing for work, and they’re all to be considered throughout the bread baking process, and whether or not I’m physically recording these variables, I’m always making mental notes in my head of how the dough is interacting with its local atmosphere.
Happy Baking!


Nate Iannuccillo, Weather Observer/Education Specialist

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