The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

yeast storage

Sparkie's picture

yeast storage

I spoke with the folks at Fleishmann's today and this is what I gleaned.


Heat kills yeast , not cold.

The problem with freezing yeast is water. It creates water crystals that either rupture or spear the yeast cells, killing them.

"fresh yeast"has such a high % or free water freezing is death.

 I told them I freeze yeast all the time, in a bag with air sucked out in a sturdy sealed container, they said, (unofficially)  if you evacute the bag put in the freezer that is great, but if I suck the air out of a container then fridge it, it keeps way longer then is marked, for many years, although I am sure comapny policy is , if expired , we aren't responsible.

 they also said if I had a vacumn  device and I pulled a real vacumn on the jar it in and kep it in dark at 70 years it would last as long as in the fridge.

They also said Instant and Rapid rise are same thing and there is almost no difference from them and active yeast.

 And that there is no big difference from any of the dried yeast as far as cell count of live or viable cells fer ml are concerned.


I will now make my self a jar sealer for vacumning the stuff in mason jars, and anyone who does, realize this IS NOT the same as boil vacumn sealing food. By pulling 29 inches of atmospere out we remove all the moisture. That plus heat degrade the yeasties, our buddies.



this IS the tastiest spot on the web!



Wisecarver's picture
Wisecarver (not verified)

Thanks a bunch. ;-)

dougal's picture

sparkie wrote:
They also said Instant and Rapid rise are same thing and there is almost no difference from them and active yeast.

sparkie wrote:
And that there is no big difference from any of the dried yeast as far as cell count of live or viable cells fer ml are concerned.

I'm sorry, but I fear that the call-handler you spoke to would seem to be misinformed regarding the difference between 'actively dried' and 'instant-mix' yeasts.

This misinformation would seem to often extend to the advice to use the same quantity of both. And Fleishmann's are among those guilty of selling Active Dry and Instant in same-size sachets, and claiming their equivalence.


Product names such as "Rapid Rise" are often downright misleading.

Use the same quantity of Instant to replace Active Dry, and the rise will indeed be more rapid - at the expense of bread quality, rapid staling, etc. Its just the same as adding more (live, working) yeast to get a more rapid rise -- because that is EXACTLY what you are doing. 



Here's what King Arthur Flour believe

Active dry yeast is live yeast that’s been dried, a process that kills up to 70 percent of the yeast cells. These dead cells surround the live cells, acting as a cocoon to protect them. For this reason, you must “proof” active dry yeast — dissolve it in water, to expose the live cells — before baking with it. ...

Instant yeast is also live yeast, but it’s been dried at a much lower temperature, and using a different process. Only about 30 percent of the cells are dead, and therefore it begins to work much faster than active dry yeast...
The numbers KA quote are rather higher than most people's (but note that they are actually suggesting there are more than twice as many live cells in Instant Mix).

Nevertheless KA's numbers do illustrate the considerable difference between the two types.

Source of the quotes:


You might also note that Paula Figone, in her book "How Baking Works" writes:

Every pound of Active Dry Yeast contains about a quarter pound of dead yeast cells. ...  ... the drying process (a fluidized bed) that produces instant yeast is much gentler than the one used for active dry yeast, so while there are some dead and damaged yeast present, there is not the same high level.

See it on Google Books (very long url shortened)


This information is common to many respected Bread-Baking writers, Glezer, Hammelman, Dr Buehler, etc

Fleishmann's seem to be disagreeing with everyone!


To be charitable, the Fleishmann call-handler may have been given wrong info by his company's PR people. Otherwise, it would be interesting to know where he learned that nonsense.

It would be interesting to see if Fleishmann's could provide any independent evidence for their remarkable and unorthodox statements.

Is it as simple as Fleishmann having invented Active Dry, and not invented Instant?

They certainly seem to be responsible for much of the wrong information circulating about Instant-mix yeast!


Incidentally, the problem with freezing (undried) yeast cells is not with "free water" -- the problem is with the water inside the microscopic yeast cells. Freeze it and it expands, damaging or destroying the delicate cell membrane.

The concern about rehydrating ANY dried yeast with the appropriate temperature water has to do with rehydrating those membranes with minimal damage. The "right" temperature is the temperature that minimises the damage!  Accordingly, different degrees of care in rehydration can lead to different proportions of dead yeast -- in both active dry and instant styles.



Dobeda's picture

I just joined this site and was checking out what is being talked about...I have always used Red Star yeast and buy it in bulk from our coop.  I keep small amounts in the refrigerator and the rest in the "deep freezer" on reserve. I never have a problem with it, no matter the length of time I store it.

spongedaddy's picture

I just finished the last of some Red Star that I kept in a ceramic coffee container -- the type with a rubber seal and latch (sorry I don't have the technical term for it). Anyhoo - it took me a couple of years to work through this batch and storing it this way never gave me anything except successful loaves.

mrosen814's picture

Do you store it in the fridge?  freezer?