The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Atmos Pressure

jcking's picture
jcking

Atmos Pressure

We're still learning about variables in baking. A few days ago I baked 2 sourdough loaves, one for me, one for my neighbor. The oven spring was less than normal - slightly dissapointed. When I gave my neighbor a loaf I appoligized for the density of the bread. She said it may have something to do atmospheric pressure. My neurons began firing. She's a stewardess and flies trans atlantic, She has a good understanding of air pressure and altitude. My rise and bake had occured during some severe weather; thunderstorms, hail, tornatic activity. I'm only a few hundred feet above sea level, did I take a Twilight Zone trip into high altitude baking?


What do you think?


Jim

Chuck's picture
Chuck

Although flying to 35,000 feet does indeed cause a very noticeable change in air pressure, I think weather causes much less. Even the worst  hurricane seems to be equivalent to moving upwards less than 4,000 feet, and a really severe storm (the kind that happens only once in a decade) seems to be equivalent to moving upwards less than 2,000 feet. So a typical storm isn't even dropping air pressure anywhere near what it is routinely in Denver CO.


IMHO the temperature and humidity changes that accompany a storm are most likely much more significant for rising bread.

jcking's picture
jcking

Hey Chuch,


Yeah probably had a small effect on rise, not so much in the oven. So I'll take the weather into consideration next time we get something as severe as we had.


Thanks for your input,


Jim

proth5's picture
proth5

thinking about your post because I bake in - Denver, CO.


The things that we generally experience is that bread dough rises more quickly (because the pressure from the CO2 produced by the yeast has less pressure to push against) and all things being equal we tend to get plenty of oven spring.


A thing that happens with cakes and such is that we get so much expansion so quickly that the gluten/starch does not fully harden before the leavening gives out, causing collapse.  Common wisdom is to bake hotter (there is an urban legen that ovens sold in Denver have a mysterious "adjustment" that makes them run hotter.  Not!) and add more flour (to slow down rising).


Of course, our altitude also comes with very low humidity and that brings its own challenges.


Your problems seem to be the opposite, so I would attribute them to other variables (not to be anthropomorphic about it, but your levain may "feel" more sluggish in damp, stormy weather.)


For fun, you could buy an inexpensive altimeter and see what your effective altitude would be under various storm conditions and see how your bread reacts.

jcking's picture
jcking

Back in 2000 I lived in North Glenn, CO. near THorton, for a year. Know what you mean about the dry, could'nt keep my lawn alive.:) Didn't bake while I was there. Sluggish MaMA could have caused it, I posted this to see what others might think, and I thank you for your perspective. I like the brainstorming that happens here. Silly ideas can lead to new good ideas.


The less than normal size of the loaves is no big deal, it only happened this once. Silly me has one of those Casio watches that measures Barometric pressure, so next time extreme weather and baking collide I'll take some notes. I wonder if the phase of the Moon may come into play :) So many variables--so little time.


Jim

Mini Oven's picture
Mini Oven

is one phenomena that most people don't think about.  A house door slamming when all the windows are shut or worse, slamming the oven door, can cause cakes and lighter egg batters structures to fall.  I think we can eliminate living near an air base where the planes like to test breaking the sound barrier, those booms can sink a soufflé and wake up babies.  


On a smaller scale, thumping the jar of pickles on the bottom to loosen the vacuum seal is the same.  It sends a shock wave thru the juice and eventually hits the seal, just enough to make opening the jar easier.  This might also be accomplished if the oven door slammed before the gel is setting in the loaves.  I can only think this a problem with an almost over-proofed loaf.   Thumping a loaf on the bottom to test doneness is no danger to the loaf, the loaf has set already.


I've not yet experienced bread doing any of this but I never pushed it slamming my oven door and the drums are played in the basement.  I have also not banged my finished loaves down hard on anything after removing from the oven.  (I want them to be as high as possible for my pictures!)  My guess is that your loaves proofed faster than normal and that is how you lost some height.  They caught you off guard.  (The little doughy buggers!) Try getting the loaves in sooner when the humidity is high.  Just a few degrees warmer can make such a big difference in rise times.  


Mini

jcking's picture
jcking

Mini,


Interesting point of view; sound and logical ideas. Thanks! Gives me other things to consider. Thunder, lightning, electrically charged particles, Spooky Action at a distance. There's a high probably it was me rather than nature, After doing something so many times one may get lazy and watch the clock, rather than the dough. I noticed another post (shortly following this one) with reference to altitude, Seems ideas in this post may be spreading like wild yeast :)


Jim