In the comments of a recent bread post, I was asked what the difference is between the available types of yeast and why I use different kinds in different recipes. Here’s what I wrote in response:
“I don’t have a scientific explanation but I can tell you how I use them differently.
Dry active yeast: This is the kind I always proof first so it’s what I use for any type of bread that I’m afraid to make without testing the yeast, which usually includes larger loaves and/or a dough with a lot of “stuff” in it. This type of yeast is not nearly as “hungry” as the rapid rise variety so the dough takes substantial time to rise and usually is more dense once baked. [added note here: this means the dough is sturdier so it can support larger sizes and more ingredients.]
Rapid rise yeast: This kind I almost always mix straight into the flour without proofing it. I like to use it for rolls and similar smaller airy dough creations, such as bread sticks. It lives up to its name in that a dough made with rapid rise yeast will double in size in about 30 minutes instead of two hours. Why not always use it, you ask? I personally think the flavor of the resulting bread is not at “deep” (i.e., hinting of sweetness from the yeast’s gas) when it rises so quickly. I’m sure there’s a more scientific reason too that a real artisan bread maker could explain.
By the way, there’s also something called easy blend yeast, and I think it’s a combination of the more traditional dry active yeast and the rapid rise. I had a few packs of it once, but don’t really see it all that often in the supermarket.
All in all, I’ll try to do some research and figure out more factual answers to your question. I’ll put up a yeast primer if I can get enough materials together.
Really good question, btw!!”
And indeed it was a good question, and one I wanted to answer for myself. Luckily for me, the answer was right under my nose the whole time. My copy of The Big Book of Bread contains more than five whole pages explaining the properties of this essential ingredient in bread making. Turns out I wasn’t too far off in my gut instincts about what to do with which types and why.
For rapid rise yeast, which the book dubs “fast-action (quick) dried yeast”, it explains this variety is “a combination of dried yeast and the bread improver ascorbic acid (vitamin C), which accelerates the action of the yeast during the fermentation process” and is “sprinkled and mixed directly into the flour or dry ingredients…making yeast cookery quicker and easier.” They also note that this is the preferred yeast for those using bread machines. They note that rapid rise yeast does not technically require a second rising period, but they highly recommend it, which leads me to believe that they have the same thoughts as myself about rapid rise yeast not imparting the same depth of flavor when it rises so fast. Allowing it to rise a second time will give it more of an opportunity to develop that flavor. Regardless of the questionable factual nature of that theory, a second rising does ensure a more evenly textured loaf. If you let rapid rise yeast get out of control and rise too fast or too long, the dough may collapse and result in a sad looking loaf.
For dried active yeast, also referred to as “traditional” or “ordinary” dried yeast, the book says it “is compressed yeast from which the moisture has been removed…this type of yeast will need to be reactivated with water prior to use” and resulting dough will require two rising periods. This is not the type of yeast to use in a bread machine.
Coincidentally, the book offered some other interesting yeast facts that I found quite useful. Rapid rise yeast keeps longer than dried active yeast (the former up to 12 weeks, the latter only about 2 months). Also offered was a rough guide of measurement/ratios which goes something like 2 teaspoons of rapid rise yeast is equal to 1 tablespoon of dried active yeast and both those measurements will support up to 5 cups of flour. Keep in mind though that the more fats (butter, eggs, and milk) you add to a dough, the more yeast you’ll need as fats slow down its feeding frenzy on the sugar and starch. Same goes for salt, although the book does not that salt helps preserve the bread so don’t ever skimp on it too much.
The book also comments that all varieties of yeast, even fresh yeast which is a tad difficult to find, can generally be used interchangeably in recipes so long as you abide by the rough equivalents above. And most importantly, remember that as soon as any kind of dried yeast comes in contact with even the teeniest bit of moisture, it’ll jump out of its hibernation and start eating. Unless you use it promptly, it’ll be ruined. I’d suggest putting all your yeasts in a ziplock bag and storing them on your fridge door, which is almost assuredly dry and cool.
Interestingly enough, the book says yeast will still activate in cold water. I was always under the impression that cold water would basically kill yeast. But apparently it just takes a lot longer to show signs of life and mixing a dough and letting it rise in the fridge overnight may actually result in “a good, well-shaped loaf.” I might just try that next time.
Oh, and I almost forgot: the book lumps “easy-blend” yeast with rapid-rise yeast so they must behave very similarly after all. See, I’m learning just as much as you guys from these SFTF Weeks of Bread!