Hi all, it’s back to school time here at Caterpickles Central, which means my annual summer hiatus from blogging about the random questions that pop up in our lives is over.
But before I get into today’s question, I’d like to mention that while I may be an indifferent blogger over the summer months, I am an excellent Back to School Mother. I know this because:
a) I don’t post back to school pictures on my Facebook account, Twitter feed, or blog.
b) I do bake batches of End of the First Week of Middle School brownies.
I used a brownie mix, of course, because I also have a house to clean, a summer’s worth of laundry to do, bills to pay, and a book to write. Which brings us to today’s question.
I normally skip over high altitude baking instructions because they have never been relevant to my life, but today, for whatever reason, they caught my eye.
My brownie mix said to add extra flour and water in high altitude locations and I couldn’t help but wonder why.
Why do you have to change your baking recipes at higher altitudes?
I don’t know how much time you spend at the King Arthur Flour website, but now that I bake my own bread 15% of the time, I visit their website pretty frequently to trouble-shoot various baking calamities. So of course, I trundled over there immediately to see what their baking experts had to say about this issue.
True to form, the King Arthur website has several charts talking about how to adjust the oven temperature, liquid, sugar, and flour to compensate for the effects of baking at high altitudes. They advise changing one ingredient at a time to see what works, and to keep in mind that what works for your neighbor up (or down) the mountain may not work for you. But while the King Arthur website provides lots of glorious detail on how to compensate for the effects of baking at a high altitude, they don’t spend much time explaining why all that compensating is necessary. They mention once that the lower air pressure is to blame, and leave it at that.
Clearly, I needed to look elsewhere if I wanted to glimpse the science behind this particular cooking anomaly.
Fortunately, The Accidental Scientists at the San Francisco Exploratorium have a lovely and detailed article on just this issue. The lower air pressure at high altitudes affects baked goods in two ways:
- They rise more easily
- They lose moisture much more quickly
Let’s look at each of these one at a time.
Why do baked goods rise more easily at higher altitudes?
I’m going to assume that you, like me, are used to dumping baking soda, baking powder, and yeast into your batters and doughs without thinking too much about why you’re doing it. Briefly, chemical leavening agents like baking soda and baking powder help baked goods rise by creating carbon dioxide pockets when mixed in the batter and heated. Baker’s yeast, on the other hand, interacts with the sugar in your dough to create pockets of carbon dioxide (and apparently other things that flavor the bread).
These chemical reactions happen much more quickly in a low air pressure environment. Lower air pressure means less force from the surrounding atmosphere to counteract. As a result, the gas bubbles created by the leavening agents grow faster and larger. If you’re lucky, the worst outcome will be a cake or a bread that is more coarsely textured than you’d like. But if you have my luck in the kitchen, what will really happen is that the gas pockets created by these chemical reactions will expand so quickly and so forcefully that the air pockets burst and your cake collapses.
Now for the second question.
Why do baked goods lose water more quickly at higher altitudes?
It turns out that water only boils at 212°F at sea level. Everywhere else, the boiling point of water is affected by a number of factors, including air pressure. Water boils (or evaporates) when its internal vapor pressure equals the pressure exerted on it by the atmosphere. At sea level, achieving this equilibrium takes 212°F worth of heat. Higher altitudes walk hand in hand with lower air pressure. And the lower the air pressure, the lower the temperature at which water will boil.
What does this mean for baking? Basically, the water vapor (or steam) which helps your baked goods rise will be generated more quickly (and dissipate faster). Your bread, cookies, cakes, and brownies will be drier and the sugar in them more concentrated. Your lovely baked goods will stick to your pans. Your cakes won’t set, or if they do, they will be astoundingly dry.
So, will adding extra flour and some extra water to my brownie mix fix it?
Maybe. Maybe not.
The effects of baking at high altitude vary depending on how far up or down the mountain you are. That extra dose of flour and water might do enough in some places, but if you’re serious about your brownie texture, you may need to do some extra experimentation. The real answer may be to reduce your oven temperature or shorten the cooking time. Or maybe you need to cut out some of the sugar or add an egg white.
- High Altitude Baking (King Arthur Flour)
- The Science of Cooking: The High Art of Baking at Altitude (The Exploratorium)
- Why does water boil faster at higher altitudes? (Wonderopolis)