You may not know it, but yeast is everywhere: on the surface of fruits and vegetables, in the lees at the bottom of craft beer bottles, in the soil, and even on your skin. But we most commonly associate these fabulous fungi with leavened bread.
What Does Yeast Do in Baking?
Yeast is a single-celled organism that makes bread rise. Yeast cells feed on simple sugars, which in baking are provided by flour. As the yeast cells digest sugar, they give off carbon dioxide gas, and that’s what makes bread dough rise.
The busier the yeast cells, the faster the dough rises. Baking kills the yeast and sets the structure of the loaf.
Enzymes and compounds are other byproducts of this digestion, and these change the texture and flavor of bread.
What is Baker's Yeast?
The baking yeast you buy at the store is all the same species, Saccharomyces cerevisiae. It’s available in different formats, dry and fresh.
Commercial baker’s yeast was first developed in the late 1800s. It was fresh and had a short shelf life. During World War II, America’s Fleischmann’s Yeast came out with the first active dry yeast. It had a much longer shelf life and was easy to store, which made baking bread on a whim more accessible for home cooks.
Wild yeast – the stuff that populates a sourdough starter – is the opposite of commercial yeast. Before commercial yeast, bakers used sourdough starters or barm (the yeasty foam at the top of fermenting liquids) from their nearby brewery. Multiple strains of wild yeast can be present in a culture at a time, and they are more tolerant of acidic environments, so they can thrive in tangy doughs and offer a wider range of flavor than commercial yeast.
Types of Baker's Yeast
Active Dry Yeast
What it is: The original granulated yeast, typically sold in envelopes.
Common brands: Fleischmann's, Red Star
How to store: Sealed active dry yeast keeps for about two years. Once opened, active dry yeast will keep for four months in the refrigerator and six months in the freezer.
Do you need to proof it? No, actually! For years, it was necessary to proof active dry yeast in water before adding it to dough, but manufacturers have since changed the product so that’s no longer necessary. You can now add active dry yeast straight to recipes without proofing it. If you prefer to continue proofing it just to be safe, go right ahead! It won’t hurt anything.
Substitutions: If you need to use active dry yeast in place of instant yeast, just multiply the amount in the recipe times 1.25. For example, if the recipe calls for 1 teaspoon of instant yeast, use 1 1/4 teaspoons active dry yeast.
Also called: Fast-Acting, RapidRise, Bread Machine yeast
What it is: A more vigorous dry yeast. Instant yeast was developed as a non-proofing alternative to active dry yeast, back when active dry yeast needed to be proofed. Nowadays neither need to be proofed, but instant yeast remains more potent and reactive than active dry yeast, and benefits from hydrating before being added to dough.
Common brands: SAF, Fleischmann's, Red Star
How to store: Sealed instant yeast keeps about two years. Once opened, instant yeast keeps four months in the refrigerator and six months in the freezer.
Do you need to proof it? Instant yeast does not need to be proofed, but it does take some time to dissolve in the dough. For maximum activity and for better distribution in the dough, we recommend adding instant yeast after the autolyse, a short period of resting after an initial mixing of the flour and the water.
Substitutions: To use instant yeast instead of active dry, multiply the amount in the recipe by 0.75. For example, if a recipe calls for 1 teaspoon active dry yeast, use 3/4 teaspoon instant yeast.
Also, instant yeast goes by many names, but they are all utterly interchangeable.
Fresh Cake Yeast
Also called: Cake yeast, compressed yeast, fresh yeast
What it is: Cake yeast has the texture of crumbly cheese. Professional bakers love using fresh yeast because it’s made from strains of yeast that are very active.
Common brands: Fleischmann's, Red Star
When to use: Crumble fresh yeast directly into the dough, unless the recipe advises to dissolve it in water first. You’ll see it called for mostly in either very old recipes, or recipes from professional bakeries that have been adapted for home cooks. Fresh yeast is more hydrated, which helps it distribute better throughout dough. It’s not essential to use fresh cake yeast; active dry or instant yeast will do just fine (see below for how substitution tips).
How to store: Cake yeast has a short shelf life and needs to be refrigerated. Buy it from a store with a good turnover and always check the best-before date. You can refrigerate cake yeast for up to two weeks. Do not freeze.
Should you proof it? There’s no need to proof fresh yeast, unless you suspect it’s expired.
Substitutions: If you can’t find fresh cake yeast that’s truly fresh, it’s fine to sub active dry yeast. One 1/4-ounce packet active dry yeast (i.e. 2 1/4 teaspoons active dry yeast) equals 0.6-ounce cube of fresh cake yeast.
1. What’s the difference between active dry yeast and instant yeast?
The main difference is the amount required to leaven bread. Instant yeast is more powerful, which is why you can use 3/4 the amount of instant yeast as you would active dry yeast.
Another, now outdated, difference is how you add these yeasts to doughs. For decades, active dry yeast needed to be proofed before adding it to dough. Instant yeast was developed to add directly to doughs, without proofing.
However, yeast manufacturers have since tinkered with active dry yeast and you can now add it straight to the dough. Nowadays the main difference between the two is the amount of yeast you need for a recipe. If you’re using instant yeast, it’s a little less.
2. Is rapid-rise or quick-rise yeast the same as instant yeast?
Yes! You can swap one for the other. These products all work the same way, though their coatings and particle size may vary.
3. How much yeast is in a packet?
One packet of yeast is 7 grams, or .25 ounces. It measures out to 2 1/4 teaspoons.
4. My bread didn’t rise. Why?
Yeast is alive. Just like you, it thrives under certain conditions. Adding liquid above 140 degrees will kill it. It also doesn’t like cold temperatures. If your kitchen is 68°F, it’s going to take longer for a dough to double in bulk than it will in a 75°F kitchen.
Sugar feeds yeast cells, but too much sugar can inhibit its growth. If a bread is already sweet, like our panettone, increasing the sugar can result in a loaf that’s sluggish to grow. For high-sugar, low-moisture loaves, use osmotolerant instant yeast like SAF Gold. (Osomotolerant just means yeast that can thrive in doughs that have high amounts of salt or sugar.) You’ll need to order it, though; it’s not widely available in stores.
5. What is nutritional yeast?
Nutritional yeast is a flavoring and supplement that’s heat-dried, so it’s deactivated (i.e., not to be used for leavening). It’s flaky like fish food and has been fortified with B vitamins. It has a delightfully cheesy umami flavor and can be added to recipes, like this polenta.
6. What is brewer's yeast?
It is a by-product of brewing beer. Like nutritional yeast, it’s deactivated. Its flavor is different, though; it’s bitter, and sometimes a little beery.
7. Is yeast gluten-free?
Dry yeast and fresh cake yeast used in baking are gluten free. Other types of yeast may not be.
8. Is yeast vegan?
Yeast is a single-celled organism with no ability to feel pain. Most vegans consider yeast to be vegan.
9. How do you proof yeast?
We have a quick take on this right here.
10. How do you store yeast?
We recommend the freezer or fridge. Learn more here.