How to Rehydrate Dry Yeast for Beer

In terms of rehydrating dry yeast for beer, the information seems to be all over the place.

On the one hand, do you even need to rehydrate dry yeast for beer?

Plenty of brewers seem to be direct pitching and doing just fine.

On the other hand, what are the risks of direct pitching, and is there a specific route to take when working with dry yeast?

The answer, as with most things, is “it depends.”

Dry Yeast

Dry yeast can be a huge benefit to some brewers as it is shelf stable for much longer than liquid yeast, lasting up to 2 years under proper storage conditions.

It is created by manufacturers who dehydrate liquid yeast with a careful process that allows for the survival of most of the original yeast cells.

During the dehydration process, yeast cells go dormant and should revive rather quickly under the proper rehydration conditions.

However, because many yeast strains cannot tolerate the dehydration process, there are far fewer strains available to brewers purchasing dry yeast than in the liquid yeast variety.

You can purchase virtually every single strain that has been discovered in liquid yeast form.

At the same time, and for that very reason, dry yeast is much more affordable than liquid yeast.

Making the decision to go with dry yeast or liquid yeast is a tricky one, and must therefore include a lot of forethought in terms of budget, cost of production, and the size of and number of your batches.

If you plan to make large, or multiple, batches, you may be better off going with liquid yeast.

If your production is still rather small, and you are in the experimental stages with your flavors and aromas, you may want to choose the dry variety as it gives you more wiggle room in terms of gaining experience and not risking too much money up front.

Rehydrating Dry Yeast

The biggest problem with rehydrating dry yeast is the potential for destruction of the yeast during the process.

Once yeast cells have been dehydrated, the cell wall is incredibly vulnerable to damage once rehydration is attempted.

When attempting to rehydrate yeast in water, a loss of up to 60% of viable cells has been reported, if the process is not handled correctly.

This is because cell walls lose the ability to regulate what passes through them, meaning they cannot differentiate between what comes in and what goes out. Yeast can effectively then simply turn to useless mush during rehydration.

Similarly, attempting to simply pitch dry yeast directly into the wort can also result in loss of cell viability because, again, the cell walls are vulnerable. Sugars and other ingredients in wort can leach directly into the yeast cell, damaging the contents and killing the yeast.

At least when directly pitching dry yeast into wort, the loss seems to only come in at about 30% of total viability loss, but still, if you can avoid loss at all, so much the better.

The goal should always be to maximize on yeast viability for pitching, so you can count on a predictable and consistent batch every time and follow the same practices throughout.

And now we know that if not handled properly, you can end up with a loss either way.

Thus, the key, if you decide to go with dry yeast, will be to rehydrate correctly and carefully, whether you use water or directly pitch.

How to Rehydrate Dry Yeast for Beer

In Water

When rehydrating dry yeast with water, your primary focus must be on the temperature.

Too cool, and the hydration process is too slow, leaving those cell walls vulnerable to major damage.

Too hot, and you kill your yeast no matter what.

You also want to ensure you are using sanitized tap water, ideally with some hardness to it. Distilled or filtered water runs the risk of decreasing your cell viability.

To rehydrate your dry yeast, sanitize your packet and your scissors, then pitch your packet of yeast into a pot of sanitized tap water at a temperature between 95 and 105 degrees Fahrenheit. Your water should be 10 times to the weight of your yeast for total absorption and preparation to pitch into your wort.

Sprinkle the yeast into the pot evenly and wait 15 minutes.

After that initial waiting period, gently stir the yeast in the pot to thoroughly hydrate it and wake it up. Then leave it for 5 more minutes.

Finally, slowly lower the temperature in 5 minute intervals to the temperature of your wort, and when the temps match, go ahead and pitch it in.

In Wort

To pitch the yeast into your wort directly, you must be working with a lower gravity beer.

Why?

Lower gravity beers mean fewer fermentable sugars are present in the wort, so you have much less concern over those sugars damaging your cell walls.

You may still lose some viability, but likely not enough to affect your fermentation.

Be sure you sanitize your yeast packet and scissors and then sprinkle the yeast packet evenly over your prepared wort surface.

Again, wait 15 minutes for yeast to rehydrate on the surface of your wort and then gently stir the mixture to fully combine it.

You should see your yeast become active within a few hours to a day, depending on your strain.

In the end, the benefits of working with dry yeast are myriad, from saving money to saving time.

In the name of efficiency and consistency, if you find a dry yeast you love, and love to work with, taking this route is recommended.

Just be sure to always take your yeast viability measurements along the way so you can track your progress and create your own step by step process for your best batches.

Cheers!

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Sources:

  1. https://www.northernbrewer.com/blogs/brewing-techniques/the-importance-of-being-hydrated-dry-yeast-handling
  2. https://www.lallemandbrewing.com/docs/products/bp/BEST-PRACTICES_REHYDRATION_DIGITAL.pdf
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