Every two or three years, my wife and I clean out our pantry, because life has a way of adding a few extra things along the road.

And when we finally get down to it, we find all sorts of expired products that we had completely forgotten about — cans of old beef stock, snacks that have gone stale, and dried herbs or spices that have long lost their potency.

We were doing precisely that this weekend when I stumbled upon a couple of expired packets of Fleischmann’s Rapid Rise yeast. Not one to waste food in any shape or form, I couldn’t help but wonder: Could I still use it?

Using Expired Yeast

Yes, you can use expired expired yeast, but your dough will probably take longer to rise. Once yeast is past its prime, it loses its vitality and is slower to ferment dough and make it rise. Use expired yeast for simple, starchy doughs, and not for enriched doughs like brioche or pastry that require a lot of leavening power.

Enriched doughs are fattier and more decadent since 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, expired yeast.

Yeasts are tiny, single-celled creatures that feed on the starches in flour when exposed to warmth and moisture. Once they start to eat, they fart out gas bubbles (carbon dioxide) and alcohol (ethanol) as a byproduct of their digestion.

This process, called fermentation, ameliorates the dough in more than one way: The gas bubbles get trapped in the thick and dense protein mesh, making it rise. The alcohol, on the other hand, lends a richer aroma to the dough and makes it more flavorful.

The Types of Yeast (And Why It Matters)

You’ll find three types of yeast in most grocery stores: fresh yeast, active dry yeast, and instant yeast, each with its own shelf life and storage method.

Fresh yeast, also called “cake yeast,” is highly perishable due to its high moisture content. It’s stored in the fridge and should be used up within 2-3 weeks of purchase. (Fresh yeast keeps for 3-4 months in the freezer.)

Active dry yeast and instant yeast are yeast with much of the moisture removed, making them shelf-stable. They can be stored in the pantry, where they’ll keep for a few years.

Active dry yeast is basically granules of dehydrated yeast cells. Inside these granules are living — 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 inside from the elements.

Instant yeast, also called “rapid-rise” or “quick-rise” yeast, is yeast that goes through the same dehydration process as active dry yeast. However, it consists of much finer granules that don’t need to be rehydrated and can therefore be mixed directly into the flour instead.

How to Check If Yeast Is Still Active

Few things are as frustrating as trying to bake bread with an expired packet of yeast, only to find that the yeast is no longer usable and your loaf has not risen at all despite a whole day of waiting.

That’s the risk of using outdated yeast. The good news is that you can prevent this from happening by checking if the yeast in your fridge or pantry is still active before using it in your flour mix.

What Does Yeast Smell Like?

Yeast that hasn’t been proofed — fresh, active dry, or instant yeast — smells earthy. After proofing, yeast smells “yeasty” and a little stale, like the last sip from a glass of beer that’s sat on the table for a little too long.

Expired yeast doesn’t smell or taste any differently than fresh yeast. The only way to find out if old yeast is no longer active is to proof it by mixing it with lukewarm water and waiting 10 minutes to see if it begins to bubble.

Other Uses for Expired Yeast

Is there anything you can do with expired yeast packets other than throwing them in the trash? Here are a few ideas if you, like me, 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’s more than 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.

Takeaways

Nine times out of ten, you should be able to pull off making a dough with expired yeast. The dough will rise slower, but it will still rise.

That said, it’s a good idea to proof the yeast beforehand. By doing so, you can make sure that enough of the yeast cells are still alive, which means the dough will leaven.

If, during the proofing process, you find that the yeast is no longer active … then pour it in your compost pile or water your plants with it.