Q&A. Find answers, Ask questions

Q&A is a concise way to get help on the products and solutions we offer.

You’ll find below the frequently asked questions from our community of clients and partners.


To enrich this sequence, you are encouraged to ask any product or process related question that helps you with your buying or creating decision.

Distribution of the fermentis yeasts (world perimeter)

Where can I find/ Buy your yeasts?

Fermentis yeast is available worldwide through a wide network of distributors. You can find them all here:  https://fermentis.com/fermentation-solutions/find-our-distributors/


Can I re-use a sachet of 500 grams once opened?

For the 500g sachets, we don’t recommend to re-use open sachet. However, for a sachet where the air has been flushed and firmly closed, we have experienced that the sachet can be stored for one week in a refrigeration temperatures and still be fine for use. Be aware that after storage, the yeast sachet need to be kept at ambient temperature until the yeast comes back at ambient temperature.


This process works only one time.  Indeed, when you take the sachet out of the fridge and come back to ambient temperature, you will have some humidity formed by the change that you won’t be able to remove. Humidity is the second enemy of active dry yeast, after the air.

Re hydratation of the yeast

What are the advantages/disadvantages of water v. wort rehydration?

The main thing you need to know about the rehydration of the yeast, is that it should be done in a sterile medium. Either way, the water or wort need to be sterile.  If you chose water, you boil and then you decrease the temperature of the water to avoid killing the yeast. That’s the main disadvantage. The advantage is that in the sterile water the yeast won’t start to growth (no sugar), you can conserve it in sterile conditions / t° condition longer than into the wort, because CO2 will start to be formed.

I've read that rehydrating in wort as opposed to water can decrease viability: is this true?

No, that’s not true.  There is the potential for a slight loss in viability (approximately 3-6%) but that will not impact the fermentation at all.

I see the recommended rehydrate temp for ale yeast is 25~29°C? My pitching temp for ale is 18°C. Will this not "stun" the yeast?

The recommended rehydrate temperature is an optimal temperature.

Outside this optimal range (as long as the temperature is above 10°C), you will not stun the yeast but you could get a longer lag phase at the beginning of the fermentation.

Of course, this point is depending of the others factors influencing the fermentation (quality of the wort, fermentation temperature, starting gravity, etc…).

How many water can you recommend to us to start the rehydration in?

The optimal ratio is for our yeast is 1/10. The yeast is not very sensitive to the ratio of yeast to water. If you go over the ratio of 1/10 you could have technical issues, due to the higher viscosity.

Can you clarify if it is correct that no oxygenation is needed or not for your dry yeasts? And would there a difference between lagers and ales on this?

We don’t recommend aerating the wort in normal conditions. The dry yeast has been produced and dried with a specific know-how of the Lesaffre Group, in order to maximize the Ergosterols content of the cells. This allows the yeast to grow/multiply and ferment well.

However, you could aerate the wort in particular cases, for example if you recycle the yeast. There is no difference (for the O2) between Ale and Lager.

Do you recommend using a rehydrating agent?

We actually do not recommend any rehydrating agent. Even though it will not harm the yeasts, we don’t see any positive effect with our range. In fact, we believe that if there is an effect, it is related to the nutrients added in fermentation. So, adjusting the nutrition in the fermentation is more than enough.

Pitching rate

What is the best pitching rate for my Ale beers?

The recommended pitching rate for our Lager strains in a first use of active dry yeast is from 80 to 120 g/hl, corresponding to 7 to 11 million cells/ml and for Ale from 50 to 80 g/hl corresponding to 3 to 5 million cells/ml.

It is linked to the fact that our standard dosage in our packaging is around 10×10^9 cells/gr. On packaging, we are not mentioning the standard results but the absolute minimum guarantee so 6×10^9 viable cells/gr.


It is a general guideline that doesn’t take into consideration the different phenotypes of the yeasts. Different yeasts have different kinetics (see more in our Tips&Tricks)

If I pitch more yeast that the recommended 80g/hl, perhaps 150g/hl, is there any downside, negative impact on the final beer?

In a first use of active dry yeast, by increasing the pitching rate, you will reduce the fermentation time and the risk of autolysis.

For example, if you double the quantity of pitched yeast, you will gain one multiplication cycle, so a shorter fermentation time. The pitching rate could modify the flavor profile but it’s very hard to define a general rule: it depends of the strain but also of the raw materials used.

Propagation of the yeast

Does over-aeration increase the likelihood of diacetyl formation?

We know that after 18 hours of fermentation, adding oxygen increases the diacetyl and aldehyde levels.

Quality and tracability

Are the Fermentis yeasts Gluten Free?

We do not dose any Gluten in our products because in our factories the raw materials of our yeasts are Gluten Free.


The yeast strains produced by the LESAFFRE company for the production of Fermentis active dry yeasts do not contain any Genetically Modified Organisms (GMO), as defined by 2001/18/CE European directive dated 12 March 2001 (which stand in for the 90/220/CEE European Law).

As a consequence, we guarantee that Fermentis active dry yeasts are not subject to any further conditions of labeling regarding the directives 1829/2003 and 1830/2003.

I note that E491 is used as an emulsifier in your dried ale yeasts. Is said E491 of vegetable or animal origin?

The Sorbitan Monostearate (SMS = E491) is an emulsifier authorized for the dry yeast.

The specifications of the SMS used by Fermentis are in conformity with the FAO / WHO requirements, the Food Chemicals Codex and the EEC. Fatty acids used for the SMS synthesis are from vegetable origin.

Saccharomyces cerevisiae is usually mentioned for ale, while here it is used for lager. The fermentation temperature is higher than what is typical for lager.

The yeast taxonomy (the way we classified yeast) have been modified following the advancement of the genetic sciences.

Today, it is considered as lager yeast, saccharomyces yeasts being able to metabolize melibiose (which is a particular sugar) when Ale yeast are not able to.

Lager and Ale yeasts are classified under Saccharomyces cerevisiae.

Can we use Fermentis active dry yeast for the production of an organic beer, as if they’re not certified organic?

The European legislation allows brewers to use non-organic yeast in organic beer production.

Refermentation process

What is the most adapted strain for the refermentation?

For refermentation, try using our SafAle™ F-2.

The SafAle™ F-2 will consume first the simple sugars (Glucose), then the Fructose. This strain respects the aromatic profile of your beer, and won’t give any other flavor to your final product. Another advantage is that this yeast provides a nice haze (no flocs) and sticks to the bottom of the bottle.

General question

Where does yeast come from?

Yeast occurs in the environment but, contrary to popular belief, not necessarily in vineyards. Scientific research has shown that microorganisms are carried by wind, humans, birds, and especially insects (wasps, bees and flies). Since no birds or insects are specific to a single plot of land or terroir, the idea that each yeast is land- or terroir-specific is not established even though recent researches showed a recurrence of few strains among hundreds identified on a same location. As a matter of fact, the yeasts strains responsible of the spontaneous fermentation (less than a dozen) are unpredictable.

Yeast populations contain a wide range of strains, which are constantly migrating. For example, some yeast found in the Kemeu River vineyard in New Zealand are the same as European yeasts in… French oak barrels! Thanks to new genetic analysis tools, all yeast strains can now be accurately identified.

Where does yeast go at the end of alcoholic fermentation?

Yeast dies at the end of alcoholic fermentation and settles to the bottom of barrels/cuves.


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