How to Check if Yeast is Still Good + Substitutions if It's Bad

If you’re baking and don’t know how long that yeast has been sitting in your kitchen, there are easy ways to see if it’s still good. Yeast is actually a microscopic organism, and it slowly dies out if you don’t use it. Whether you have active dry or instant yeast, we’ll walk you through a quick way to check if it’s still alive and active. We spoke with professional baker Craig Watson to explain how to determine if yeast is still good as well as signs that yeast has gone bad to watch out for.

How do you know if yeast is good?

Craig Watson, a professional baker, recommends a proofing test. Combine ¼ cup (60ml) of lukewarm water, ½ teaspoon of sugar, and 2 ¼ teaspoons of yeast. Let it sit for 5-10 minutes. If the yeast is bubbling or foaming, it’s still good to use.

Section 1 of 6:

How to Test if Yeast is Active

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Combine warm water, yeast, and sugar in a bowl. Watson recommends proofing the yeast to test its freshness. The test works for active dry yeast, instant yeast, and fresh yeast. He breaks down the following instructions:^{[1]
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Craig Watson
Baker

Expert Interview}
- Heat ¼ cup (60ml) of water to about 100–110°F (38–43°C) so it’s lukewarm, but not hot.
- Stir in ½ teaspoon (2 g) of sugar.
- Add 2 ¼ teaspoons (7 g or 1 packet) of yeast.
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Look for foam and bubbles after 5-10 minutes. Watson says that after a few minutes, “The mixture should start to foam and bubble, creating a frothy top. This means it's alive and active.”^{[2]
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Craig Watson
Baker

Expert Interview}
- Once you test the yeast and it’s bubbling, you can use it immediately for your next recipe! Some things you could start baking right now include:

Section 2 of 6:

Signs that Yeast Has Gone Bad

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No bubbles or foam while proofing Watson explains, “If there’s no foam or only a few bubbles after 10 minutes, the yeast is likely dead and should be replaced.”^{[3]
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Craig Watson
Baker

Expert Interview}
- Yeast is a living microscopic organism that creates gas when it eats, which causes bubbling and rising while proofing. When the yeast dies, then it no longer produces gas.
- If you’re in the middle of baking and don’t have time to run to the store, check out our list of easy substitutions.
Watson describes that if the yeast has a bready smell that’s slightly sweet, then it’s still good. If the yeast has already gone bad, then it will have developed a strange, sour odor.^{[4]
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Craig Watson
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Watson suggests checking the expiration date on the yeast’s packaging to see if it’s expired.^{[5]
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Craig Watson
Baker

Expert Interview} You can still test yeast that’s past the expiration date, but there’s a good chance it will not be active anymore.
If you have fresh yeast and you notice any white or green fuzzy growths on it, then it’s spoiled. Toss the yeast out right away to prevent any other spoilage in your fridge.^{[6]
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Section 3 of 6:

Is it okay to use expired yeast?

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Expired yeast is safe to consume, but your recipe might not turn out. Yeast isn’t harmful once it goes bad and it’s really unlikely that you’ll get sick from it. However, when yeast expires and doesn’t form bubbles, it’s not active and your dough won't rise properly. To ensure that your baked goods rise and have the best texture, use yeast that’s still good in your recipes.^{[7]
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- If the yeast is years old or far past the expiration date, then it’s probably best to throw it out.
- Toss expired yeast in your trash or add it to a compost bin.

Section 4 of 6:

Yeast Substitutes for Baking

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Baking soda and lemon juice Baking soda also acts as a leavening agent and will help make baked goods rise, but it needs an acid like lemon juice to work. Split the yeast measurement into an equal amount of baking soda and lemon juice as your substitution.^{[8]
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- Example: If your recipe calls for 1 teaspoon (3g) of yeast, then use ½ tsp (4.8 g) of baking soda and ¹⁄₂ teaspoon (2.5 ml) of lemon juice.
Double-acting baking powder releases carbon dioxide while you’re kneading the dough and while it’s baking to give baked goods an airy texture. Use the exact same amount of baking powder as you would yeast when you’re making your dough.^{[9]
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Section 5 of 6:

How to Store Yeast so It Stays Good

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Active dry yeast Store the yeast in an airtight container and set it in your fridge. For even longer shelf life, keep the yeast in your freezer instead.^{[10]
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Research source} Watson says, “heat and humidity kill yeast.”^{[11]
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Craig Watson
Baker

Expert Interview} While you can keep yeast at room temperature, it stays fresher when you keep it cool.
- Shelf life: 6 months in the fridge, 1 year in the freezer
- You don’t have to wait for yeast to thaw. Just proof it before adding it to your recipes.
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Instant yeast Keep instant yeast in a dry place, like a kitchen cupboard or pantry. Try to avoid areas with high-humidity or moisture. To preserve instant yeast’s freshness, place it in an airtight container in your freezer.^{[12]
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- Shelf life: 6 months at room temperature, 1 year in the freezer
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Fresh yeast Fresh yeast isn’t as common because it has the shortest shelf life. Wrap your fresh yeast in parchment paper and place it in an airtight container. Label the container with today’s date and keep it in your fridge.^{[13]
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- Shelf life: 2-3 weeks^{[14]
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Section 6 of 6:

What is yeast?

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Yeast is a single-celled organism that’s used to leaven dough. Yeast is a microscopic living creature that feeds on sugars and starches. As it eats sugars, yeast releases carbon dioxide that forms pockets of air that causes your dough to rise and grow in size.^{[15]
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- Active dry yeast has been dried out and needs to be proofed before you add it to your dough.
- Instant yeast is made up completely of living cells and can be added directly to your recipe without proofing.
- Yeast also creates alcohol while it’s fermenting, but it’s removed from the dough when you bake it.

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You can use instant yeast and active dried yeast interchangeably in recipes.^{[16]
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If you have instant yeast and need active dry, decrease the amount by 25%. If you need 1 tsp (3 g) of active dry yeast, then use ¾ tsp (2.25 g) of instant.

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If you have active dry yeast and need instant, increase the amount by 25%. If you need 1 tsp (3 g) of instant yeast, then use 1 ¼ tsp (3.75 g) of active dry.

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