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I make bread about 2-3 times a week (all the bread we eat) and get yeast in a small jar (Fleischmann's), kept refrigerated. For a mid sized bread, I use 5/8 teaspoon of yeast. However, I have noticed that, the older the yeast, the less the dough rises. When the yeast is pretty old, the dough is as much as an inch below where it rises when it's new, in a KitcheAid mixer metal bowl (about 1 gal). As a result, the bread is thicker and less fluffy.

Does yeast lose strength over time and should I add a little more yeast as it ages?

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    You should be keeping that jar of yeast in the fridge.
    – FuzzyChef
    Commented Feb 5, 2023 at 0:10
  • @FuzzyChef we do
    – amphibient
    Commented Feb 5, 2023 at 0:57

2 Answers 2

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The reason why many recipes have you proof the yeast (combine the yeast and sugar and check for activity) is because yeast can go bad. This isn't a binary thing, as you suspected it weakens over time before being fully useless. You can try overcompensating with more yeast but it's a guessing game as to how much more you should be adding. Some other solutions:

  • Throw it out and get new yeast. This is probably the best solution for beginning bakers.
  • As @Stephie notes in the comments, you can simply keep the same amount and use visual cues instead of time. Often recipes will say something like 'let rise for 1 hour or doubled in size'.
  • Perform a yeast freshness test
  • Get a 1-cup liquid measuring cup.
  • Add half a cup of warm water. If you have a thermometer, it should read 110° to 115°. If not, just make sure that the water isn’t steaming or hot to the touch – you can comfortably let your finger sit in it for several seconds.
  • Dissolve a teaspoon of granulated sugar into the water.
  • Add about 2 and ¼ teaspoons (or a ¼ ounce packet) of dry yeast.
  • With your watch or timer, observe how long it takes for yeast to active. Within 3 to 4 minutes, it should start to rise. Within 10 minutes, it should be very foamy and have risen to the 1-cup mark.

The added benefit of the yeast test is that you can use it to estimate how much more yeast to add if you want to go that route. For example, if it only rises to the 3/4 cup level, you may want to double the amount.

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  • "Go bad" implies that something becomes harmful for consumption. Is that the case here, or is the yeast simply less effective? Commented Feb 5, 2023 at 9:24
  • Relying on “let rise for 1 hour or doubled in size” may not work except when it’s just at the beginning of losing efficiency. The structure of the dough after sitting for too long differs, and you’ll get bad results.
    – mirabilos
    Commented Feb 5, 2023 at 11:20
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Weird proofing story: I grew up as an expat in the 60s. We babied our US brands of yeast because it took a long time to get to us.

  • No metal
  • Proof before using
    • Give it some extra sugar to help it along

Not sure why we had no local sources for yeast.

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  • Welcome to SA! This doesn't appear to be an answer to the question the OP asked, though. Can you explain better?
    – FuzzyChef
    Commented Feb 9, 2023 at 23:35

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