Does Yeast Go Bad

So you’ve bought a package of dry yeast some time ago, and it still sits in the kitchen cabinet unopened. Last time you checked, it was nearing the best-by date on the label. Now you’re ready to prepare some homemade baked goods but aren’t sure if the yeast is still okay to use. Does yeast go bad?

Or maybe you decided to be a bit fancier this time around and bought fresh yeast instead. Then you got busy with other issues, and that package you’ve purchased still sits in the fridge two weeks later. Can you still use that package, or should you discard it?

While going bad of yeast in the traditional sense (i.e., being moldy and unsafe to eat) is not that common, there’s also the matter of effectiveness. While the chemistry is different, the general idea is similar to the potency of baking powder.

Yeast that won’t make your bread rise and become soft and fluffy is of no use. So the more important issue here is knowing if your yeast will do its job. Fortunately, there are ways to test if this fungus is still active and usable. Read on to learn more about storage, shelf life, going bad and proofing yeast.

Fresh and dry yeast on old wooden background.
Fresh and dry yeast on old wooden background.

How To Store Yeast

There are two kinds of yeast available on the market: dry yeast and fresh yeast. The former is the more popular one and lasts much longer. The latter is said to produce better quality dough and therefore often used in artisan bakeries and by cooking enthusiasts. Let’s start with the first one.

Dry yeast is a bunch of yeast granules in a dormant state, waiting to be activated.

You should store an unopened package of dry yeast in a cool and dry area. Room temperature or slightly below is perfect. That means the pantry or a cupboard in the kitchen away from the stove are great options.

Once you first open the package, it’s time to refrigerate or freeze the rest. Dry yeast is very perishable when exposed to air, moisture, or heat and requires refrigeration upon opening.

Line of baked bread rolls
Three bread rolls in a line

Please note that putting the package as-is into the fridge isn’t a good idea because the moisture from the fridge will easily get to the yeast. Instead, you should either transfer the granules into an airtight container or put the package into a resealable freezer bag.

Also, when you’re ready for baking, remember only to take as much yeast as needed and promptly put the rest back into storage.

Fresh yeast is available in the refrigerated section of the store, and you should keep it in the fridge at all times.

Just like with dry yeast, when you need it, cut off as much as the recipe calls for and put the rest back to the refrigerator.

Baker's yeast
Baker’s yeast

How Long Does Yeast Last?

Dry yeast usually comes with a best-by date on the package. And while many products with a best-by date often last much longer beyond that date, for dry yeast it’s not a given.

Generally, if the unopened package is nearing the date on the label, make sure to test its effectiveness before baking bread.

Once you open the package, the yeast should retain its effectiveness for about 4 months when stored in the fridge and 6 months in the freezer.

Of course, those dates are rough estimates. It’s not unheard of for the yeast to stop working even earlier.

Baked bread rolls with sesame seeds on top
Bread rolls with sesame seeds on top

Fresh yeast is basically a living organism that stays active (and therefore potent) for about 2 to 3 weeks after production.

A package usually has a use-by date, and you shouldn’t expect yeast to stay potent for much longer. Of course, sometimes it might happen, but just as well it might become inactive even earlier.

If you know you won’t be able to use the rest of the package, freezing fresh yeast is a good solution to that problem.

Active dry yeast (unopened)Best-by date  
Active dry yeast (opened) 4 months6 months
Fresh yeast Use-by date 

Please note that the periods above are rough estimates. Yeast often remains potent for longer, but that’s not the norm by any means.

Naking ingredients: powdered yeast and fresh yeast
Baking ingredients: powdered yeast and fresh yeast

How To Tell If Yeast Has Gone Bad?

When it comes to dry yeast, the symptoms of going bad are similar to other dry ingredients, like flour. That means clumping together, forming solid chunks, od any signs of water or organic growth.

For fresh yeast, it’s discoloration, drying out, or any signs of mold.

If you notice any of the symptoms, discard the package. Please note, however, that more often than not your yeast will look and smell perfectly normal. And if that’s the case, and the product is nearing the end of its period of effectiveness described earlier, you should check if the yeast is still active before using it in a baking project.

Baking with yeast
Image used under Creative Commons from Adam Sharron

How To Test Yeast Effectiveness

By proofing the yeast, you make sure that the dough you will prepare, will turn from this (just mixed dough for my bread rolls):

Fresh yeast dough before rising
Dough before rising

to this (same dough after rising for 90 minutes):

Fresh yeast dough after rising
Dough after rising

Checking yeast effectiveness (or proofing the yeast) is pretty similar for both dry active and fresh yeast. You only need some warm water and sugar to do it.

For dry yeast, you need 1/4 cup of warm water (105° to 115°F, or 40° to 46°C is ideal for the yeast to grow, 140°F or 60°C and above will kill the yeast), 1 packet of dry yeast (2 1/4 tsp) and a teaspoon of sugar. Mix it well and leave for 10 minutes. If the mixture foams up to about 1/2 cup mark, it’s potent enough to use.

For fresh yeast (or cake yeast), many recipes have the proofing process built-in or you can add it in yourself.

You start with half a cup of water or milk (90° and 100°F, or 32° to 38°C) and dissolve 1 teaspoon of sugar in it. Then you add the cake yeast, mix it well and leave for 10 minutes. After 10 minutes you should notice a lot of foam. If that’s not the case, discard the yeast. If there’s a ton of foam, you can add the rest of the ingredients needed for the dough.


Please remember to decrease the amount of liquid added by half a cup and add one less teaspoon of sugar, since those are already added.