March 21, 2024 - 10:50am
Baking at Sea Level
I live on an island in Puget Sound at an elevation of 200 feet. I have been baking sourdough bread for the last 4 years and have found that it takes longer for my bulk fermentation than stated in most recipes. I thought at first I was just not doing something correctly since it took 2 to 4 hours longer to ferment than stated in the recipes I was using.
Now I think elevation is the culprit and I just adjust my baking schedule to compensate. I make excellent sourdough it just takes a little longer. Pie crusts and other baking appears to be unaffected.
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It won't be 200 ft of elevation that makes a difference. Heck, I lived at 6200ft/1900m in a desert and my fermentation times didn't seem different.
TomP
There's an atmospheric pressure calculator here: https://www.omnicalculator.com/physics/air-pressure-at-altitude
I entered sea level pressure (psi) at 14.696 (looked it up), altitude at 200', temperature at 70F. Got 14.592 psi of pressure. Did it for 6200' and got 11.8201 pounds per sq in.
How much difference that makes to the dough, I have no idea, but it's got more air pressure weighing it down at 200'.
Just looked up my elevation. I'm at 620' and 14.358 psi. That psi was already shown on the info sheet for my town, I didn't calculate it.
The atmospheric pressure at 200 ft elevation is very slightly lower than at sea level. That small difference can happen just from normal weather variations.
The effect of lower pressure will show up more in the reduced boiling temperature and increased evaporation than anything else. At 6000 ft boiling temperature of water is about 201 deg F instead of the standard 212 deg F. You will never be able to bake your bread to an internal temperature of 208 deg F!
I've never noticed a material difference that I didn't write off as having to do with temperature, or the relative performance/activity of my starter compared to the recipe. For that matter, I've made my regular bread at 5800' in the Tahoe area, and with similar temps as I use at sea level, my timing was pretty much dead on.
Not sure how much that helps.... :)
Rich
So, Tom, you are saying that the change in pressure is too small to make a noticeable difference and weather conditions can cause changes in air pressure, too.
I just remembered that my local weather network always reports air pressure. Right now, it's 1026mb which converts to 14.88psi, around .5 change from what I posted originally.
This subject is interesting. PNW Guy, do you know your water boils at 211.4°F? Mine boils at 210.7. My husband's boiling point is around 100F, I'd say.
Water's boiling point changes by .5F° every 250', above and below sea level. Aside from the heat, how would dough rise in Death Valley? And just how much change in air pressure is required before leavening is affected? We know high altitudes affect it, but does that mean at all elevations below about 2000', it's not noticeable?
I used to travel from my low humidity New Mexico home at 6200 ft to my moderately high humidity (but air conditioned) Virginia home at around 700 ft twice a year. I would carry my starter with me. I never noticed much of a difference in baking bread in either location. I didn't bake cookies or cakes so I can't speak to them.
Aircraft altimeters have to be adjusted to account for the current barometric pressure. Every pilot knows that the indicated altitude at a given airport can vary by dozens to hundreds of feet depending on the local atmospheric pressure at a given time. It can change during a flight. You need to take that into account if you are flying a plane but not for baking bread.
You mentioned 1026 mb. In the eye of a very strong hurricane the pressure can drop as low as 960 mb, or 13.92 psi.
Based on my beer making experience water boils here at about 210ºF. My kitchen temperature is around 68ºF the year around because it rarely gets over 80º in summer.
Have you compared your ambient temperature to the temperature(s) recommended by the recipe writers? If the temperature at your location is several degrees cooler, that would lead slower yeast growth and longer fermentation times.
Paul
I use my oven with the light on to bulk ferment, I can achieve about 77-78ºF temperatures that way. My kitchen temperature is about 68º year round due to being surrounded by 60º water. I have good luck doing overnight bulk fermentations because of the lower temperatures.
I had the same problem, (I"m in the Vancouver area,) until I followed a Jefferey Hamilman recipe to the letter. If he said mix for 3 minutes I set the timer, if he said 80 degree water I measured. I found that the breads I made this way were perfect. In the end I realized a couple of things, 1. our water has a LOT of chlorine, and I started using water from my Britta filter, which helped. 2. Dough temperature matters. I shoot for between 76 and 80 df before the bulk ferment. There are a lot of variables to making bread. Eventually you will figure it out. If a longer ferment is working then good for you! Happy Baking.
I also have started to pay close attention to dough temperature. I found a formula that uses room, starter, and flour temperature to determine the temperature of the mixing water. Seems to work well.