How to Use Dry Yeast While Brewing Beer

Yeast is the magic in your brew. Without it nothing happens. Yet many hobby brewers put very little thought into the yeast they use or how they handle it. Yeast is somewhat resilient, allowing many a brewer to get away with poor selection, less than stellar handling techniques, and lower then optimum pitching rates. These practices seem to be even more prevalent when dealing with dry yeast, especially in the wake of the popularity of wet yeast and the coinciding rise of the idea that dry yeast is somehow inferior.

Don’t get me wrong, whether liquid, dry, or slant grown, yeast treated poorly can still make beer. It may even be worth drinking. But you are not allowing the yeast to work for you at full capacity by any means, and stressing yeast almost never bodes well for the taste of a beer.

This article is going to focus on the proper way to use dry yeast because it is under appreciated by much of the homebrewing community. If used and treated correctly though, it can be a great for the homebrewer.

Pros and Cons of Dry Yeast

There are a few pros to using dry yeast. First, dry yeast has come a long way. The idea that dry yeast is inferior to liquid yeast had validity a few years ago, but today’s dry yeast is of better quality and is cleaner than it once was.

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Pros:

• Under the right conditions dry yeast can be stored the longest (I’ve had to throw out-of-date liquid yeast packets away, but was able to still brew because I happened to have some dry yeast.)
• It has the largest number of viable yeast cells.
• It is also cheap. Most liquid and slant grown yeast run $7 or more, while dry yeast averages around 3 dollars.
• No need for a starter. Dry yeast comes with all the nutrients they need to get started and placing dry yeast in a starter just depletes that nutrients. All it needs is rehydration.

Cons:

• The biggest con is probably lack of variety. There are a lot more styles of liquid yeast then dry yeast.
• The pro of not needing a starter, actually creates a small con, in that you cannot harvest a clean yeast culture from the starter.

Over Pitching / Under Pitching

Over pitching and under pitching can both cause problems in a finished beer. Each can cause increased levels of acetaldehydes and diacetyl; and change the ester profile. Under pitching causes slow fermentations, long lag times, and better conditions for contamination of the wort by bacteria and wild yeast. While, at some level, pitching too much will start to affect the health of the yeast.

The upper end of the optimal pitch-rate window is a lot wider than the lower end, so it is better to error high then low and over pitching is widely considered the more forgiving of the two. In short, it is better to over pitch then under pitch.

Pitching Rates

Many homebrewers under pitch without realizing they are even doing it. An extreme example from my own brewing experience is the very first time I tried to brew anything.

It was a mead, and being completely new to any sort of brewing, thinking it was better to be frugal, and having read the rule-of-thumb guideline of 0.5 grams of yeast per liter of wort, I opened a package of wine yeast and carefully measured out about 2 grams for my one gallon batch of mead. Now, I had several other problems going on that I had failed to consider (good temperature control and taking into account the higher alcohol of a mead being two of them), but needless to say very little happened and my first attempt at hobby brewing was a bust.

So, what’s a good pitching rate? Well let’s look at some of the info available. Fermentis yeast analysis sheets show their yeast having 6 billion viable cells per gram at packaging, which equals around 69 billion per package. Not really that high a number, but realize this is their minimal estimate. The packages are more likely to have anywhere from 10 to 20 billion cells per gram.

Viable Yeast Cell Approach

This is the formula generally used to determine cell count for a brew.

The pitching rate can range from 0.75 million for ales to 1.5 million for lagers and will have to be played with a bit to find the ideal rate for a given recipe.

Milliliters of wort is figured by converting gallons to liters (≈3.79 liters/gallon) and multiplying that by 1000 milliliters / liter. So, a 5 gallon batch would be:

To convert specific gravity to degrees Plato we use the formula:

So, say our original gravity is 1.056.

Incidentally it is very easy to find conversion tables and calculators online to make these steps faster, but it’s always good to know the math.

So, now an example. I’ll use the widely considered standard pitching rate of 750,000 cells (for an ale), our 19000 milliliters of wort (5 gallons), and degrees Plato will be 14°P (1.056 SG).

We would need 199 billion yeast cells for a 5 gallon batch of average strength wort. If we assume the low end of the 10 to 20 billion per gram range we need:

If, on the other hand we assume the high end of 20 billion we’d get our cell count out of 9.9 grams of yeast or one 11.5 gram pack.

In my opinion, assuming the lower end (10 billion) and using more yeast is going to help more then it’ll hurt in most cases. Use two packs of rehydrated yeast. But, also remember, nothing supersedes good results and consistency. If you find you like the results from a single pack, by all means keep using one pack.

Obviously we are generalizing here because we don’t have a true yeast cell count, so if you have a microscope and can actually do a yeast cell count several times on a given yeast strain you’ll have a much more accurate number to work with. But at least this gets us closer to good pitching rates.

Grams per Liter Approach

This approach is based on grams of yeast per liter of wort and coincides with the dosage instructions found of the Fermentis yeast analysis sheets. For all but there lager yeast, Fermentis recommends a dosage of 50 to 80 grams per hectoliter of wort. We can change this to liters easily by dividing by 100, which gives us 0.5 to 0.8 grams per liter.

Again, 19 liters in 5 gallons of beer, so:

If you’ll notice, at 0.5 grams we get very close to the same amount as we did assuming 20 million viable cells, which I’m guessing is what whoever came up with that rule of thumb was working from. I only point this out to show there is some amount of consistency between the two approaches.
And we could even figure out the dosage of a single 11.5 gram pack.

11.5 / 19 = 0.6 grams per liter; which falls within the manufacturers dosing rates, but using two packets (23 grams) puts your pitch rate at 1.2 grams per liter which is actually close to the upper range of what commercial breweries pitch.

Remember that your dosage rates will have to be adjusted for higher gravity beer (above 1.065 SG) and cooler temperature fermentations, such as with a lager or California Common.

Rehydrate

Do you rehydrate your dry yeast? I’m not sure where homebrewers got the idea that they could get away with pitching dry yeast straight into the wort.

Don’t.

In the book Yeast: A Practical Guide To Beer Fermentation by Chris White and Jamil Zainasheff it is highly recommended that you rehydrate. They cite a fact any homebrewer should pay close attention to… sprinkling dry yeast into wort kills at least half the viable cells!

The one case where it would be better to pitch straight into the wort is if you are unsure of sanitation. This would be especially relevant to new brewers, who are still figuring out there cleaning and brewing practices. But, if you are going to pitch straight in, double your pitching rate. Looking at the numbers we came up with above, this would mean, at the very least, pitching two 11.5 gram packets. The cells will still be stressed and they won’t make the beer they could have, but at least there will be enough. Of course you then have the issue of dead yeast cells — a bunch of dead yeast cells — which can adversely affect flavor.

Rehydration Steps

Rehydration is not a hard process, as you will see, but there are some things you need to pay strict attention to. Sanitation is critical during this process. Once the package is open the yeast is vulnerable to contamination; adhering to a high standard of cleanliness cuts down on the chances of something other than the yeast ending up in your beer.

Temperature is the other vital player here. Yeast has a rather narrow range of conditions in which it can survive and it is very sensitive to temperature shock. Warm water is important as the cell membranes re-form. If the water is too cold you can kill a high number of the cells.

Ideal rehydration temperatures vary between strains, but generally range from the mid 90s up to around 104°F.

1. Allow the yeast to come to room temperature.
2. Sanitize a glass bowl (StarSan works great).
3. In the bowl, pour water (some hardness in the water is good) at a temperature just a little above the recommended hydration temperature for the yeast strain (the bowl will likely lower the water temperature). You want 10 times the yeasts weight in water. So, if you are preparing 11.5 grams you’d want 4 ounces or about half a cup.
4. Check the temperature.
5. Once it is at the ideal temperature for your yeast strain sprinkle in the yeast without letting it clump up anywhere.
6. Let it sit for 15 to 30 minutes, then gently stir it.
7. Once you start seeing the yeast “set-up” stir it again to make it creamy.
8. Now, slowly adjust the temperature of your rehydration toward the temperature of your wort. You can do this by adding small increments of wort to the yeast bowl.
9. Once the temperature is within 15°F of your wort you can pitch it in.

Summary of Key Points

• Rehydrate your dry yeast.
• Once opened, dry yeast packets should be used within a few days. It’s usually better to use a whole packet then try and save a portion of it.
• If pitched without rehydration as much as 50% of the yeast cells will die.
• If pitching without rehydration, double your pitching rate.
• Sanitization and temperature control are critical for successful rehydration.
• You want at least 0.75 million viable cells for ales and up to 1.5 million for lagers.

It should be understood that there is no set amount of yeast that’s optimal for every brew. This information is only a starting point to help get you closer to a proper pitching dose. Each recipe may ferment best with a slightly different amount of yeast pitched. If you plan to brew a recipe more than once or are working toward perfecting a recipe, it wouldn’t hurt to break up a 5 gallon batch into 5 one gallon fermenters and experiment with the results of different amounts of yeast.

Also, other conditions affect your yeast. Fermentation temperature, nutrients, oxygenation, and many other factors all play a role in the yeast’s ability to perform its magic. But there’s no reason to handicap your fermentation right off the bat by under pitching. Using enough healthy yeast, at the very least, gives your brew a better chance of becoming something great.

Cheers!