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out-of-date yeast

Wulfsige's picture

out-of-date yeast

I use a Panasonic bread-making machine, usually with much success. However, twice recently I had bread which hardly rose at all, and the heavy slab that emerged was doughy. Then I noticed that the tin of dried yeast (the usual brand from a supermarket) was out of date. Does tinned dried yeast last beyond its 'use by' date, or should it be thrown out and replaced when that date passes?

happycat's picture

Why not test it with warm water to see how active it is?

mariana's picture

Yes, yeast will lose its potency with time. It loses about 10% of its power in four months after opening the tin, if kept refrigerated. As time goes by it will get weaker and weaker.

You can either discard it and use freshly purchased yeast, or increase the amount of old yeast in the recipe.

How much? I do not know, you would have to find out from experience how much old yeast would work as well as 1 tsp of freshly bought yeast for example. Try to use 25% more.  For example, instead of 1 tsp yeast add 1 1/4tsp.

phaz's picture

I've always found about 3 yrs and ya start to notice a difference. After it starts to go south it's still usable, but more will be needed. Enjoy! 

suave's picture

I use a bag of yeast that has expired more than 4 years ago.  I think it may be starting to lose power, but this is a new development for me and I have not tested it against a frash pack.  That of course does not mean yours is not dead, so just buy a new one, it's cheap, and there's no longer a shortage.

DanAyo's picture

Wulf, you may find something(s) of interest HERE.

Kistida's picture

I enjoy these articles shared by all you experts here. I remember I had an old container with less than a teaspoon expired instant yeast ruminating at the back of my fridge back when bakestuff aisle were bare in most places. I used pinches of it in poolish with lukewarm water, and kept it in the oven instead of the cooler counter. That helped me make some bread, just a lil longer to proof but was worth it.

- Christi

Mini Oven's picture
Mini Oven

Funny you should ask...  found ten 7g foil packages of instant yeast yesterday in my cupboard.  I hadn't seen for a while ...expired April 2020.  Just bought yeast and putting it away when, low and behold, this stuff showed up. a package and do a sniff test for rancidity.  If it smells yeasty, light in color, and dry...then a wet test.  

Wet test:  

Sprinkled about half a teaspoon into a jar and added about 100g lightly warm water.  Stirred and watched taking photos.  First photo is thin milky. Bubbles in middle are from stirring.  Smells yeasty.

Second photo 30 min later shows separation, more water on top with a cloudy light mixture on the lower half. No obvious bubbles at this time. One die-hard bubble from stirring still floating in the middle.  Smells yeasty. Yeast when they get all active will most likely start stirring the separated liquids.  Watch and see what happens.

  So now what?  I decided to add 5g AP flour and give it a good stir then wait. The flour separated making a layer on the bottom and then I gave it another hour in a warmer spot.  I can just about see tiny gas pearls forming on the top front edges, in the meniscus.  There is still live yeast but not a lot.  Yeast will multiply if given food and time, so.... This looks like it could be put into a poolish or preferment with more flour and allowed to ferment longer or add a generous portion of the expired yeast and make a dough keeping an eye on it with a good amount of patience until it doubles in volume.I started the wet test around 10 am and by 2:20pm (14:20) I added enough flour to get a thick batter.  Let it rise undisturbed at 24.8°C and now 8 hours later need to make a decision.  Either put it into a bigger jar, thicken it up and use it tomorrow (it's almost 10 pm)  make a dough, or retard this or a dough to use tomorrow.  It is pretty much a small poolish right at this moment and smells fresh and lovely.  It's already to the top edge of the small peanut butter jar. 
happycat's picture

Love it... working with what's there and building something off it. Nice.