Yeast is a living organism and that means it can die. Here’s how to check if it’s still alive (and what to do if it isn’t).
I was cleaning out my pantry the other day when I dug out a couple of old packets of Fleischmann’s yeast, the Rapid Rise type. I looked at the expiration date and, lo and behold, they had expired a little over two years ago!
Reluctant to throw the packets of expired yeast in the garbage and curious if they’d still leaven dough, I googled the topic. But all I found were conflicting opinions on forums and a lot of gibberish written by people who had clearly never yeast (or baked) in their lives.
For all of you home cooks who are wondering if it’s okay to use expired yeast or not: I researched it, tried it, and I’m about to give you my best advice—free from the usual B.S. and fluff—below.
So, what’s the verdict? Can you bake with expired yeast?
You can use expired yeast, but it will take longer for the dough to rise. Yeast past its prime has lost much of its potency and needs more time to ferment and leaven the dough. Use it for simple, starchy doughs and avoid enriched doughs, like brioche or pastry.
Enriched doughs are fattier and more decadent because they contain dairy or animal fat. They also need more leavening power to rise, which is why they’re not the best kind of dough to make with older yeast packets.
Yeasts are tiny, single-celled organisms that feed on the starch and sugar in dough when given proper moisture and warmth, farting out gas bubbles (carbon dioxide) and alcohol (ethanol) as a byproduct.
This process, known as fermentation, ameliorates the dough in more than one way: The gas bubbles get trapped in the thick and dense dough and make it rise. The alcohol, on the other hand, gives it a richer aroma and makes it more flavorful.
The Types of Yeast (And Why It Matters)
There are three types of yeast in the supermarket: fresh yeast, active dry yeast, and instant yeast. Their shelf life and recommended storage differ.
Fresh yeast has a high moisture content, which makes it highly perishable. It must be stored in the fridge and used up within a few days of opening. Active dry yeast and instant yeast are dehydrated, and therefore shelf-stable. They can be stored in the pantry, where they will keep for a few years.
Fresh yeast, also known as “cake yeast,” has a lot of moisture and is highly perishable. It must be stored in the fridge, where it will keep for 2-3 weeks, or in the freezer, where it will stay good for 3-4 months.
Active dry yeast consists of granules of dehydrated yeast cells. Inside these granules are live—but dormant—yeast cells that need to be brought back to life with water. On the outside are dead yeast cells, which protect the cells on the inside from exposure to the elements.
Instant yeast, also known as “rapid-rise” or “quick-rise” yeast, is yeast that goes through the same dehydration process as active dry yeast. Except that it’s ground into finer granules that don’t need to be rehydrated and can be mixed directly into the flour instead.
How to Check If Yeast Is Still Active
There are few things as frustrating as making dough with an old packet of yeast, only to find that the yeast cells are no longer active and the dough has not risen at all after waiting for hours.
Such is the risk of using dated yeast. The good news is that you can prevent it from happening by checking if the yeast in your fridge or pantry is still alive, or active, before you make a dough with it.
To check if the yeast in your fridge or pantry is still active, especially when it’s past its expiration date, proof it.
Add 1 teaspoon sugar and 1 packet of yeast (a packet of yeast equals 0.25 ounces or 2 1/4 teaspoons) to 1/4 cup lukewarm water. Stir the mixture and let it sit at room temperature for 10 minutes.
If it bubbles and begins to smell yeasty, then the yeast is still good. If it doesn’t, this means that most of the yeast cells have died. In such a case, it’s very likely that the yeast won’t make your dough rise at all, and it’s best to discard it.
Relevant: The Complete Guide to the Types of Yeast
What Does Yeast Smell Like?
Yeast that hasn’t been proofed—whether fresh, active dry, or instant yeast—has a slight earthy odor. After proofing, the yeast should smell yeasty and a little stale, like the last sip of beer in a pint glass that’s been sitting on the table for a while.
Despite lore to the contrary, expired yeast doesn’t smell or taste all that different than fresh yeast. The only way to determine if expired yeast is no longer active is to test it by mixing it with lukewarm water and waiting 10 minutes to see if it begins to bubble.
If the yeast starts to bubble, this means that some or most of the yeast cells are still alive and the yeast can indeed be used for baking. If it doesn’t, the yeast cells are dead and won’t leaven the dough.
Other Uses for Expired Yeast
Is there anything you can do with expired yeast packets other than throw them in the trash can? Here are a few ideas for those of you who want to avoid food waste.
Turn old yeast packets into fertilizer for your garden. Just dissolve fresh, active dry, or instant yeast in a half gallon of tap water, then water your plants with it. Don’t do this too often; once a week is quite enough.
Baker’s yeast contains fiber, protein, vitamins (vitamins B1, B2, B3, B5, B6, B9, and C), and minerals (calcium, iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc). For these reasons, it can act as a valuable nutrient for the flowers and plants in your garden.
Add dead yeast to your compost bin. Yeast, as we’ve already established, contains many minerals and nutrients, so it will enrich any compost. Add the yeast and mix it in, turning the pile to make sure it mixes evenly with all parts of it.
Nine times out of ten, there is nothing wrong with making a dough using expired yeast. The yeast leavens the dough slower than usual, but it still works.
Still, it is a good idea to proof the yeast beforehand. By doing so, you can make sure that the majority of the yeast cells are still alive, and they won’t leave your dough unleavened.
If during the proofing process you find that the yeast is no longer active… then water your plants with the water or mix it into the compost pile. And, next time, remember to use those yeast packets sooner rather than later.