Sweet Leaf

Finding Beauty through Baking ~by Susan Baxter-Peace

Warm Rising? Cold Rising? Understanding Yeast February 4, 2013

yeast (2)When I was first learning about bread, one of the key points was that the dough needed to rise in a warm place. I never questioned this. And when I took my baking classes, this point was reinforced with a little more precision; the dough should rise in a place where the temperature is between 20C and 32C (or slightly above room temperature).

But my post from two weeks ago defied this ‘rule;’ the dough rose in the fridge, which is nowhere close to room temperature. And yet, I ended up with a couple loaves of lovely bread. How could this be?

I did some digging and discovered that letting dough rise at slightly above room temperature is the optimal temperature for dough growth, but not the only temperature for growth. Yeast becomes active when it is warmed, and with most of the yeast we use at home, moistened (commercial bakeries usually use fresh yeast, which is more like a putty texture than a dry granulated one), hence most recipes call for mixing active dry yeast with warm water for about five minutes. This wakes up the yeast, getting it ready to do its job.

Once the yeast is activated, it can be productive anywhere from 4C (normal fridge temperature) to 40C. The difference is in how long it takes for the dough to double in bulk. The lower the temperature, the longer the yeast will take to work. Hence, the bread recipe from two weeks ago needed to rise for at least two hours in the fridge, as opposed to the 45-60 minute rise time of a recipe done at room temperature. And once you get higher than room temperature (40C) the process also slows, because it is considerably warmer than what yeast likes.

So what are the benefits to cool-rise bread? It can be more convenient, if you don’t have the time to devote to the whole bread-making process at once; you can put it in the fridge and come back to it the next day to bake. It also creates more interesting flavours and textures the longer it sits – which explains the artisan-type bread from last week’s post. But don’t leave it too long! Like many things, if it is left too long to its own devices not-so-friendly bacteria can take over and leave you with an unappetizing mess! Be sure to follow a recipe until you get a feel for the timing.

You can read more about yeast and the fermentation process at Baking911 by clicking here.

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