Every now and then, the home baker will run into a recipe that requires compressed or cake yeast. Most of us are used to using what is known as active dry yeast, which usually comes in packets or jars in an almost granular-looking form. But compressed yeast, which most often comes in two ounce to one pound cakes, finds its way into lots of home applications too. It’s helpful to know how to use both, as well as how to substitute one for the other. Here’s a little information on each to help you get started.
Active Dry Yeast is one of the most common forms of yeast in home baking and in some countries (including the US) it’s far easier to find in stores than any other form. Part of its preference in the home bakery comes from its shelf life. Unlike compressed yeast, which must be used within a couple of weeks at most, active dry can keep for a very long time. While it keeps best under refrigeration, you can actually store dry active yeast at room temperature for several months before it loses potency. It usually comes in ¼ ounce packets or jars of varying amounts. As far as taste goes, it imparts a bit of a sharper and more fermented flavor to your baked products than does compressed yeast. It does require a bit of preparation to activate properly. The best method for this is to sprinkle it on top of water heated to 105-115 degrees. Once the water shows some foam forming (usually about 5-10 minutes), the yeast is active for use.
Compressed yeast, despite the downfall of its faster perishing time, is far superior to dry active yeast in the speed at which it becomes active and the length of time it stays active. It won’t keep nearly as long as dry active yeast in storage, but can be frozen for several months (it’s best to give it a full 24 hours of defrosting before use). While it does not need the same activation technique as the dry active does, some prefer to soften it in lukewarm water (70-80 degrees) before use. Its flavor tends to be a little milder than dry active yeast and tends to impart sweeter tastes (ideal for softer breads such as an Italian or French bread).
You can play around with using each kind as a substitute for the other when you want to try different characteristics of flavor and activity. The conversion rate for doing so is as follows:
1/4 oz, or 2 1/4 tsp, or 7 grams of Dry Active Yeast is equal to 2/3 oz, or 19 grams of Fresh Compressed Yeast.