The Fresh Loaf

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The relation between time and temperature for fermentation

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ultrasonic11's picture
ultrasonic11

The relation between time and temperature for fermentation

Hi,


so I've been reading a lot about artisan bread baking and I'm trying to understand as much as I can about fermentation.  The conventional wisdom says that when you're letting dough rise, a cooler temperature will slow the fermentation, allowing the yeast to bring out more flavor from the dough.  This sounds reasonable at first thought, but when I thought about it some more I became confused with why is it any different than raising the temperature and allowing the yeast to work faster?  As long as you haven't killed the yeast it is still converting sugars into CO2 and ethanol, thus doing the same thing regardless of temperature.  I'm not convinced that slower time gives the yeast more time to interact because it still rises to the same level as a dough that is sitting in higher temperature, it just does it slowly.


So to make a long story short, "bringing out more flavors" feels far too hand wavy to me.  Can someone explain the nitty gritty as to why slower fermentation is better?


 


-Hoi

rideold's picture
rideold

Try it and see for yourself.  I think there is more going on than just the yeast interactions.  I can't remember all that I have read about it but I can taste a difference for sure so that's why I go for longer fermentations.  I'm more of a fan of room temperature fermentation with smaller amt. of leaven or yeast than the retarded fermentation in the fridge.

arzajac's picture
arzajac

I used to homebrew beer a lot.  The different tastes (or off-tastes) are really obvious in beer brewing.  At high temperatures, yeast creates esters and other chimicals that can smell like banana, plastic or acetone.  You avoid these by keeping the yeast at a lower temperature during the fermentation period.  This is the big difference between and ale and a lager.  An ale is brewed at room temperature and has a harsher taste than a lager, which is brewed at a low temperature over a long period of time.  Lagers are known for their smooth flavour.


While making bread, I have often left yeast to activate for a little too long at too high a temperature and have gotten a whiff of the fruity/acetone smell from my warm yeast solution.  Likewise, if I make a same-day bread that doesn't ferment very long (just enough to make it rize), the resulting bread tastes more like flour than bread.


Your reasoning is valid if you only consider the amount of sugars that are consumed and the amount of CO2 that is created.  But the flavour is developed by the by-products of fermentation which are very dependant on temperature.  Also, if you keep your dough or preferment within a good temperature range, the flavours accumulate over time, which is why a longer preferment yields more flavour.

fancypantalons's picture
fancypantalons

"allowing the yeast to bring out more flavor from the dough."


Actually, that isn't it at all.  The extended fermentation allows more time for enzymes in the flour, activated by the introduction of water, to break down the starches and proteins into sugars and amino acids, which results in more complex flavour.  This is why long-fermented breads tend to taste sweeter and nuttier.


Additionally, to a lesser degree it also gives bacteria (such as lactobacilli) time to work away at the flour, producing flavour compounds of their own (normally, the yeast would out-compete the bacteria for food).

Soundman's picture
Soundman

Hello ultrasonic 11,
Glad to see you on TFL!

No doubt about it, fancypantalons has it right. To paraphrase a long-ago popular movie, I have just one word to say to you. Enzymes. (There's a lot more to baking good bread than meets the eye!)

Read the post by dmsnyder on Phillipe Gosselin's baguettes, here:
http://www.thefreshloaf.com/keyword/philippegosselin

You'll read about an overnight "autolyse", involving just flour and water, no yeast, and the enzyme action that creates great flavor.

Yeast are essential to making leavened bread, but they're just part of the story.
Good luck in your baking!

Soundman (David)

LazySumo's picture
LazySumo

Ultra, let me agree with you completely that what yeast does, it does. Pure and simple. But it's not only the yeast, it's other critters, enzymes, etc all doing their things as well.


 


Like arzajac, I used to brew beer. One thing a brewer learns is that before yeast gets into the warm, sugary liquid that will become beer, that liquid is a hospitable home to any number of critters. The yeast (by altering pH levels and alchohol levels) adjust the liquid to be a home that is good for them, but hostile to other critters. Same thing holds, I am sure, for bread yeasts. The slower they do their environmental thing the more time the other critters have to add their flavors to the end product. THAT is where the nutty flavors come from in slow-fermented breads.


 


And arz, I agree completely: Bread baked the same day it's mixed tastes like warm flour to me. Ugh. Maybe I'm doing it wrong, but I refuse to anymore. Give me bread that's taken a day or two to build up.


 


If no one minds a little self-promotion: Ultra, yesterday I posted a thread about long-ferment bread (http://www.thefreshloaf.com/node/9671/90minute-baguettes) that you might want to try.

ultrasonic11's picture
ultrasonic11

First and foremost, I want to thank you all for the responses.  All very informative stuff. 


Enzymes make a lot of sense, and that's something I totally ignored.  Enzymes are inherent in all raw foods which is why they break down; should be no different for something like dough.


I'm actually working on a dough for Chinese steamed buns that require long fermentation times.  It's actually kinda interesting because it calls for a sourdough starter, as well as low gluten cake flour which is something I haven't dealt with before.  I'll make sure to let y'all know how it goes.


Again, thanks for the responses.


-Hoi