Does Yeast Go Bad?

Does yeast go bad or not? How do you tell if yeast has gone bad and how should you store yeast? Here's a super simple guide with all the answers.

Some time ago, you decided you would shoot your shot at making some baked goods. Fast forward to now, and you find yourself looking in your refrigerator and wondering whether the left-over yeast from last Christmas is still usable.

Does that sound familiar? It must.

Or maybe, the package of yeast you purchased is still sitting in your pantry unopened and it is past the best before date.

Maybe you are worried about falling sick from eating bad yeast, or perhaps you are a baking fanatic, and just want to maintain the high-quality baking you pride yourself on.

The common worry with old yeast is not necessarily about falling ill, but rather the performance of the yeast. Because let’s face it, if your bread cannot rise, is it really bread?

Whether you are an expert baker, or just getting started, you have come to the right place. We will take you through the fundamentals of what yeast is, how to store it, how long it lasts, and to determine its effectiveness!

Here’s the short story: your yeast will come with a best-by date, but it can easily last 2-3 months after that date, if you’ve stored it properly (in the pantry or a cool, dry kitchen cupboard). If you’re unsure about your yeast, follow the yeast performance taste. Scroll down for that!

Related:Can You Freeze Fresh Yeast?Does Baking Powder Go Bad?Does Baking Soda Go Bad?

What Is Yeast?

dry and fresh yeast

Yeast are single celled fungi. In Latin, they are called, saccharomyces cerevisiae, which translates to “sugar-loving fungi”. These little guys are experts at fermentation, which is the process that causes bread to become fluffy and tasty.

How Do You Store Yeast?

There are two kinds of yeast, which are: fresh and dry yeast. Dry yeast is much more commonly bought, and fresh yeast is of higher quality and usually used by baking enthusiasts and bakers.

For dry yeast, it must be kept in a cool and dry area around room temperature when it is unopened. A kitchen cupboard or pantry is perfect for unopened packages. However, once the package is opened, it must be refrigerated.

But here’s the catch. Yeast is extremely perishable to air, humidity, and heat. So, putting the package as is into the refrigerator isn’t quite good enough. The contents should be transferred to an airtight container that will act as a seal between your yeast and the outside world.

Fresh yeast should be kept refrigerated in an airtight container.

How To Know If Yeast Has Gone Bad

Yeast brands

Here are the signs that your yeast has started to go bad. If you spot any of the below, you need to chuck your yeast!

  • Solid chunks and clumping are a sign moisture has got to your yeast.
  • Organic growth or mold
  • Discoloration of fresh yeast
  • Unusual smell

But unless you’ve forgotten about your yeast for ages or stored it badly, it’s pretty unlikely you’ll notice any of the problems above.

Instead, it’s way more likely that your yeast has degraded in quality and doesn’t work as well anymore. Therefore, you should do a yeast performance test.

Yeast Performance Test

Evaluating the effectiveness of the yeast is the same process for both fresh and dry yeast. But you’re probably wondering what exactly you’re supposed to do to test it. Well, here you go!

  1. Gather ¼ cup of water (40-46oC), a large measuring bowl, 2 ¼ teaspoons of yeast, and a teaspoon of sugar. Please note if the water temperature is over 60oC, the yeast will die.
  2. Mix the above ingredients in a large measuring bowl and wait for 10 minutes.
  3. The mixture should begin to foam up. If the foam reaches the ½ cup mark from the original ¼ cup position, the yeast is deemed effective. If no foaming occurs, or it does not reach the ½ cup line, discard the yeast.

How Long Does Yeast Last?

active dry yeast

Yeast usually has a best before date, which is generally about two years after its manufacture date. However, the best before date, how it is stored, and whether it is opened, are all necessary in determining your yeast’s shelf life.

Regarding unopened dry yeast in the pantry,

  • it will last in the pantry anywhere from 2-4 months beyond the best before date.

It will last in the refrigerator up to 4 months beyond the best before date.

You might be thinking that your opened-up yeast that’s been sitting in your fridge which hasn’t reached its best before date is probably ok.

Not so fast! For yeast that has been opened, the best before-date is useless to you. Once the package is opened, a new timer has started!

  • Opened Dry Yeast lasts 4-6 months in the refrigerator after opening, regardless of the date.
  • Opened Dry Yeast lasts 6 months in the freezer after opening regardless of the date.

Fresh yeast will last you much less time, at a measly 2-3 weeks, since there is a living organism in it that only stays potent for a few weeks.

Opt for dry yeast over fresh yeast for longer storage periods. To keep dry yeast fresh for longer, store in a cool dry place before opening and in an airtight container in the refrigerator once opened.

The Round-Up On Yeast

The key thing to stop your yeast from going bad is to prevent moisture from getting into the packet. If you do that, opened dry yeast should last 4-6 months in the refrigerator!

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Alisa Shimoyama

Alisa eats her way around the world on her travels and likes to have good food ready and waiting for her when she gets back.