A lot of people are confused about the different types of yeast and what to use if a recipe calls for one kind, but all you have is another. There are three basic types of yeast: fresh (or cake), instant, and active dry.
Fresh yeast, as the name implies, is the freshest, most active yeast you can get. Unfortunately, it has a very short shelf life and can be hard to come by.
Active dry yeast is the least active of the yeasts, so you have to use more.
Instant yeast is fairly new to the consumer market and is what many artisan bread books call for. It is more active than active dry, but not as much as cake yeast. It used to be marketed as Rapid Rise Yeast, basically because if you use the same amount as active dry, it will work faster.
So what do you do if you have one yeast and your recipe calls for another? Easy — you convert it. The table below will show you how.
Since the BBA recipes all call for instant yeast (except for the sourdoughs, of course), I’ll start with conversions for instant yeast if you want to use fresh or active dry:
Instant to Active Dry: multiply by 1.36
Instant to Fresh: multiply by 3
Active Dry to Instant: multiply by 0.75
Active Dry to Fresh: multiply by 2.2
Fresh to Instant: multiply by 0.33
Fresh to Active Dry: multiply by 0.45
To be clear, the first type of yeast listed is what the recipe calls for, and the second is what you have on hand and want to use. So, for example, if you wanted to use Active Dry yeast for the Anadama recipe, you would use 2 3/4 teaspoons yeast (2 x 1.36 = 2.72).
If you want to be sure your yeast is viable, check out this quick and easy yeast test.