Understanding and Substituting Different Kinds of Yeast

All bread begins with yeast. 

Yeast is the microscopic unicellular organism that consumes sugar and uses the energy from that fuel to create carbon dioxide, which is, of course, the gas that makes dough swell with airy, pillowy loft. Alcohol is a byproduct of the process, too; it gives a loaf a unique fermented taste.

Using the right kind of yeast is essential for producing properly risen, flavorful baked goods, but the labeling on packages can be confusing. 

Is there a difference between yeast that’s “rapid rise,” for example, versus one that’s “quick rise,” “fast rising,” or “highly active”? Some brands also purport to be best for specialized purposes, such as for pizza and bread baked in a bread machine. 

But once you understand the basics, things aren’t nearly as perplexing as they might seem. 

There are, in fact, only three types of yeast used for baking: fresh, active dry, and instant. All are derived from the Saccharomyces cerevisiae species, but each is processed from a slightly different strain of this prototypical culinary yeast.

The following primer will explain the different types of yeast and tell you how to substitute one for another when making everything from bread to doughnuts, waffles, and pizza dough. For even more information, be sure to check out our article explaining how yeast works. 

WHAT IS FRESH YEAST (ALSO KNOWN AS COMPRESSED AND CAKE YEAST)?

Fresh yeast was the first commercially available form of yeast. It is sold in soft, crumbly blocks that are about 70 percent water by weight and composed of 100 percent living cells. It does not need to be dissolved before use—fresh yeast will dissolve if it is simply rubbed into sugar or dropped into warm liquid. Owing to qualities associated with its strain, fresh yeast will produce the most carbon dioxide of all three types of yeast during fermentation. 

Fresh yeast is considered fast, potent, and reliable, but it has a drawback: it is highly perishable and must be refrigerated and used before its expiry date.

WHAT IS ACTIVE DRY YEAST?

Active dry yeasts arrive at their granular state by undergoing processes that reduce them to 95 percent dry matter. Traditional active dry yeast is exposed to heat so high that many of its cells are destroyed in the process. Because the spent outer cells encapsulate living centers, active dry yeast must first be dissolved in a relatively hot liquid (proofed) to slough off dead cells and reach the living centers.

WHAT IS INSTANT YEAST?

Instant yeasts are also processed to 95 percent dry matter but are subjected to a gentler drying process than active dry. As a result, every dried particle is living, or active. This means the yeast can be mixed directly with recipe ingredients without first being dissolved. It is in this context that the yeast is characterized as “instant.” 

WHAT IS PIZZA CRUST YEAST? 

Fleischmann’s sells a so-called pizza crust yeast that allows you to mix, stretch, top, and bake pizza all in one go, with just a few minutes of kneading and no rising time at all. 

In addition to active dry yeast, the product contains enzymes designed to relax the dough. Dough relaxers partially inhibit the formation of strong gluten networks, keeping the dough pliable and easy to stretch and making it quick to rise in the oven.

We don’t recommend this product. The structure and flavor of a top-notch pizza crust come from ample fermentation. When we mixed up a batch of dough with this yeast, the dough stretched without snapping back and rose quickly during baking—but its texture and flavor were unimpressive. The crust was leathery, not crisp, on the exterior and spongy and soft on the interior. What’s more, it was bland and devoid of the aromatic complexity that is produced in fermented dough.

WHICH TYPE OF YEAST SHOULD YOU USE?

Though the answer may change when a recipe specifically calls for one kind of yeast, in general we prefer instant yeast in the test kitchen. It combines the potency of fresh yeast with the convenience of active dry, and some consider it to have a cleaner flavor than active dry because it contains no dead cells. (We found this to be true when we comparing the two yeasts in lean baguette dough, which contains no added fat, but could detect no difference in flavor when using the two types in richer doughs made with milk, sugar, and butter.) Moreover, teaspoon for teaspoon, instant yeast contains more living cells and results in a quicker rise. 

WHAT IS THE DIFFERENCE BETWEEN INSTANT YEAST, QUICK-RISE YEAST, RAPID RISE YEAST, AND BREAD MACHINE YEAST? 

Instant yeast isn’t always sold simply as “instant yeast.” It often goes by additional gimmicky marketing names that suggest a speedier rise. You may also see it billed as “bread machine yeast,” which implies a very specific use (according to Fleischmann’s, which sells such yeast, this particular labeling is to prevent consumers from buying active dry yeast, which won’t work for dough baked in a bread machine). No wonder it causes so much confusion, even among seasoned bread bakers. 

Below is a list of some of the instant yeasts available in supermarkets. If you have any doubt, look at the ingredient list on the label. Instant yeast available to consumers usually contains ascorbic acid, whereas active dry yeast does not.

Despite their names, all of these products contain the same thing: instant yeast.

TESTING: ACTIVE DRY VS. INSTANT YEAST

We wanted to see exactly what would happen if we substituted active dry yeast for rapid-rise yeast without making any adjustments to the amount. Not surprisingly, the results were vastly different. 

We baked our sandwich bread, multigrain bread, and dinner rolls, all of which call for instant yeast, and compared them to batches made with equal amounts of active dry yeast. The active dry batches consistently took nearly 50 percent longer to rise after mixing and after shaping and baked up denser than the instant yeast batches. 

Why? These two forms of yeast have different degrees of potency, owing to their differences in processing: Active dry yeast is dried at higher temperatures, which kills more of the exterior yeast cells, making it less potent than instant yeast, which is dried at gentler temperatures. 

HOW TO SUBSTITUTE FOR DIFFERENT TYPES OF YEAST

To substitute active dry for instant (or rapid rise) yeast: Use 25 percent more active dry to compensate for the “dead weight” of the inactive yeast cells. For example, if the recipe calls for 1 teaspoon of instant yeast, use 1¼ teaspoons of active dry. And don’t forget to “prove” the yeast, i.e. dissolving it in a portion of the water from the recipe, heated to 105 degrees.

To substitute instant (or rapid rise) yeast for active dry: Use about 25 percent less. For example if the recipe calls for 1 packet or 2¼ teaspoons of active dry yeast, use 1¾ teaspoons of instant yeast. And you do not need to prove the yeast—just add it to the dry ingredients.

To substitute fresh yeast for active dry yeast: Use a ratio of roughly 2:1, i.e. use one small cake (0.6 ounce) of compressed fresh yeast in lieu of 1 packet (0.25 ounce) of active dry yeast.

YEAST FAQ

IS BAKER’S YEAST DIFFERENT FROM BREWER’S YEAST? 

Yes. Though both are the Saccharomyces cerevisiae species—and both can be used for baking or brewing—they’re bred from different strains to optimize different traits and produce different flavors and results. So if you use baker’s yeast to make beer, or vice versa, the results may not be optimal or what you’d expect.

WHAT DOES YEAST DO IN BREAD? 

Yeast functions to consume sugars and starches within dough and convert them into alcohol, releasing carbon dioxide. In doing this, yeast both leavens bread and creates flavor. 

During fermentation, two enzymes present in yeast break the flour’s starches into simple sugars. When feeding on these, the yeast releases carbon dioxide, which allows the loaf to lift and expand; alcohol, which gives the bread flavor; and a multitude of aromatic molecules, which contribute further to the flavor of the bread. 

HOW TO PROOF ACTIVE DRY YEAST

Active dry yeast must be proofed in a warm liquid before use. Dissolve the yeast in a portion of the water from whatever recipe you are using, heated to 105–110 degrees. (Avoid using water that’s too hot: Anything higher than 120 degrees will kill yeast.) 

HOW LONG DOES YEAST LAST?

Stored properly, all types of dry yeast (active and instant) have a shelf life of up to two years. When buying yeast, pay extra attention to the best-buy date. The shelf life of yeast starts when it is initially packaged, so look for the freshest one. 

HOW TO STORE YEAST

All dry yeasts stay fresh longer when stored in a cool, dry place. We prefer the freezer. After opening, active and instant yeasts have a four-month shelf life and we like to keep them in the fridge. Fresh, compressed, or cake yeast has a two-week shelf life. We also like to store it in the fridge.

HOW CAN I TELL IF MY YEAST IS STILL ALIVE?

The “best by” or “use by” date on the package should indicate if the yeast is still active, but you can also proof yeast to check that it’s viable. Dissolve a little yeast in ¼ cup lukewarm water and stir in 1 teaspoon sugar. After 10 minutes, the yeast should bubble or foam.

HOW MUCH YEAST IS IN A PACKET?

Instant and active dry yeast are often sold in ¼-ounce packets, each containing about 2¼ teaspoons (0.25 ounce) of yeast. But don’t rely on the packets to be perfectly accurate—always measure it yourself.