Cooking 101: Differences Between Types of Yeast

In my last Cooking 101 post on Why Use Kosher Salt?, I asked for suggestions on what topics you would like me to cover in future Cooking 101 posts.   I received lots of great ideas, one of which was to cover the different types of yeast.

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So, for this Cooking 101, I'd like to explain the differences between the different types of yeasts -- what they are made of, what they have in common and how to use them.

Yeast can be a tricky thing.  Sometimes, even though I usually think I understand yeast, I'll find a recipe that calls for a certain type of yeast that I either don't have on hand or don't know about. Hopefully, you will find this explanation useful and can look to it in the future as a reference.

What is Yeast?

Yeast is actually a member of the fungus family and is a living organism in the air all around us.  Baker's yeast, like baking powder and baking soda, is used to leaven baked goods (such as breads and cakes).  Baking powder and baking soda react chemically to produce the carbon dioxide that makes the baked goods rise.  Yeast, however, does not cause a chemical reaction.  Instead, the carbon dioxide it produces is the result of the yeast literally feeding on the dough.

Different Types of Yeast

Yeast comes in two forms: (1) Fresh Yeast (also called Compressed Cakes) and (2) Dry Yeast (also called Dehydrated Granules).

Fresh yeast is soft and moist and is mainly used by professionals.   It must be refrigerated or frozen, as it is highly perishable.   Fresh yeast needs to be proofed before using.

Dry yeast is fresh yeast that has been pressed and dried until the moisture content makes the yeast dormant (until mixed with warm water).  Dry yeast has a much longer shelf life than fresh yeast and does not need to be refrigerated unless opened.   Once opened, dry yeast needs to be stored in the refrigerator away from moisture, heat, and light because it deteriorates rapidly when exposed to air.

Types of Dry Yeast

There are two types of dry yeast: (Regular) Active Dry Yeast and Rapid-Rise Yeast.  Though there are some minor differences in shape and nutrients, Rapid-Rise Yeast is (pretty much) the same as Instant Yeast and Bread Machine Yeast.  This is where understanding yeast can definitely get confusing.

These two types of dry yeast can be used interchangeably, with some limitations.  Though Bread Machine Yeast is faster-rising and is specially formulated for bread machines, as its texture is finely granulated to hydrate easily when combined with flour, Active Dry Yeast may also be used in bread machines (though it but may not yield completely equal results).  The advantage of the Rapid-Rise Yeast is the rising time is half that of the Active Dry and it only needs one rising.  Though this is an advantage, you do sacrifice some flavor and texture by speeding up the rising process as the yeast does not have time to develop its own flavor.  Also, Rapid-Rise Yeast is a little more potent than Active Dry Yeast and can be mixed in with your dry ingredients directly.

How to Use Yeast

Some recipes call for dissolving the yeast first in a warm liquid and then adding this active yeast mixture to the flour while others call for the yeast first being added to the flour, followed by the liquid.  Why is this?  The dissolving of the yeast first in a warm liquid is done to make sure the yeast is fresh and active.  Since yeast is a living organism, it is possible the organisms have perished which would result in no leavening. Though this step probably doesn't really need to be done any longer because of  how reliable dry yeast is today, some bakers still feel it's a good idea to test the yeast to make sure it is still active before adding it to the flour.  Active Dry Yeast works just as well as Instant Yeast, but its instructions require you to activate it in a little bit of warm water before being added to the rest of the ingredients.

General Guide to Purchasing Yeast

Granted, purchasing yeast can be a confusing process due to different manufacturers not using the same names for their products or using the same names for different types of yeast.  That being said, here's a general guide to purchasing yeast using popular labeling and product instructions:

• Cake (Moist) - traditional live yeast; needs to be dissolved in water
• Active Dry - traditional dry yeast; needs to be dissolved usually with sugar
• Instant - contains small amount of yeast enhancer; does not need to be dissolved
• Bread Machine - exactly the same as Instant but in a different package
• Rapid-Rise - larger amount of yeast enhancers and other packaging changes to the granules; does not have to be dissolved

Can I Substitute Active Dry Yeast for Rapid-Rise Yeast?

Yes!  If you are substituting Active Dry Yeast for Rapid-Rise Yeast in a recipe, just read the instructions on the package to figure out how to activate the yeast before adding it to the recipe and reduce the amount of water (or other liquid) you add later in the recipe by the amount you use to proof the yeast.  If you are substituting Rapid-Rise Yeast for Active Dry Yeast, just reduce the amount of yeast you use in your recipe by approximately 20 percent and increase the amount of water you add to the dry ingredients by the amount that you would have used to proof the Active Dry Yeast so you end up with the same total amount of liquid in the recipe.

I hope that helps clear up the differences.  Please let me know if you have any more questions regarding yeast or have future Cooking 101 topic suggestions.