Homebrewing Pitch Rates

In my opinion, one of the simplest things you can do to improve your homebrew is to pitch the proper amount of yeast. Most beginner homebrew kits come with a small packet of dry yeast which the instructions tell new brewers to sprinkle over their cooled wort with no explanation or justification. As such, when brewers take the next step they grab a packet of dry yeast, or a pack/vial of liquid yeast, and call it good. After all, that's how they learned. Unfortunately, over/under-pitching is a common reason for off-flavors in homebrew, and by addressing the pitch rate you can quickly improve your beer!shop liquid yeast

Why should I pitch a certain amount of yeast?

Long story short, you want to pitch enough yeast to avoid two problems: under pitching and over pitching. Under pitching, or not pitching enough yeast, can lead to problems such as under-attenuation, stressed yeast, and off-flavors (such as increased ester production, DMS production, and "hot" alcoholic qualities). Over pitching is much harder to do, and it's debated what exactly constitutes "over pitching" on the homebrew scale. That said, over pitching can lead to decreased ester production.

Personally, I think that pitching the right amount of yeast is important because of consistency. The difference, in my opinion, between a good brewer and a great brewer is consistency. Can you make the same beer twice? Are you consistently making great beer? Aiming for specific numbers helps you stay consistent, and the pitch rate is no different.

Something to keep in mind is that the importance of pitching rates is somewhat debated. Some sources say that under-pitching may not be as big a deal as we think it is, while other swear by it. There are also discussions going on (fueled by this excellent article from Brulosophy) whether we should also be addressing vitality in this discussion. As with all things brewing, take notes and figure out what works for your system. Be open to change.

YEAST

What are the pitching rates?

Pitching rates are determined by batch volume, gravity, and type of yeast. Lagers have different pitching rates than ales, and a high gravity beer needs more yeast than a low gravity beer.

The formula for pitching rates is:

# of cells needed per mL of wort per degree Plato

Based on the beer you are making, you will adjust the # of cells needed, multiply it by the batch size in mL, and then multiply that by the OG in Plato.

Ale Pitching Rate

The standard ale pitching rate formula is:

.75 million cells per mL of wort per degree Plato

Not too much to discuss with this rate, it is the standard baseline for ales.

Lager Pitching Rate

The standard lager pitching rate formula is:

1.5 million cells per mL of wort per degree Plato

Lagers are heralded for their clean, ester free aroma and crisp malt character. Lagers are also often fermented at a lower temperature than ales, hence the pitching rate. On one hand, you have more cells for the initial growth phase, where many esters are formed, and more cells with help you reduce ester production in your finished product. At the same time, the lower temperatures means that the yeast will not reproduce as quickly, and so the increased number also helps keep the growth phase short.

Note that this rate is also the rate you may want to use for 100% Brett Fermentations, according to this interview with Michael Tonsmeire, the Mad Fermentationist! For more information on this subject, check out his book American Sour Beers

Hybrid Pitching Rate

The standard hybrid pitching rate formula is:

1 million cells per mL of wort per degree Plato

I often call the hybrid pitching rate formula the "high gravity" pitching rate. One of the reasons we discussed to pitch the proper amount of yeast is to decrease yeast stress. Because of the high ABV, there is additional osmotic pressure and stress on the yeast. High gravity beers are also notorious for having attenuation issues. By pitching a higher number of cells, you're ensuring that there is less stress on the yeast and that the beer is attenuated.

For anything 8% ABV or over, I'd consider using a hybrid pitching rate.

By pitching enough yeast, you're one step closer to providing the optimal circumstances for consistently great beer. Keep track of your pitching rates, take notes, and dial in your system. Happy homebrewing!

written by Matt

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7 comments on “Homebrewing Pitch Rates”

  • What's the worst that can happen from decreased ester production caused by over pitching?

    Should I always just pitch two packets/vials of I want to garuntee myself a good fermentation?

    Reply
    • Matt Del Fiacco

      Hey Stevie!

      The worst that can happen is that over-pitching causes an abundance of cells that can, in turn, rupture and cause autolysis. Cell wall ruptures, which lead to off flavors.

      The decreased ester production though isn't in and of itself a bad thing, it really depends on the style.

      To ensure a good fermentation, you should figure out how many cells you need to pitch and try to pitch that number.

      Even if you pitch two packets, at most that's about 200 billion cells. That's a good pitching rate for 5 gallons of 1.055 OG beer, but half as much as you'd need for 5 gallons of 1.090 OG beer.

      Reply
  • How do i know how many cells are in my yeast starter?

    Reply
    • Matt Del Fiacco
      Matt Del Fiacco January 13, 2016 at 1:54 pm

      Hey KD!

      For most (almost all) homebrewers, the answer is going to be an approximation. The only way to tell exactly is by counting. Thankfully, you can approximate the number pretty easily.

      With your fresh pack of yeast, see how many cells are in the pack (typically 100 billion), and then measure viability. Usually a 20% depreciation a month (I'm skeptical of this number, but it's just a rule of thumb).

      Then, with your estimated cell count, use a yeast pitching calculator to determine the starter size you'll need to increase those cells to a higher count. That number will put you in the ball park.

      Another way to estimate is visually. Check out this article from Wyeast. It details how to visually estimate the number of cells you have.

      Reply
  • Hello. I am relatively new brewer and about 6 batches ago I started using yeast starters. The rule of thumb I have been using is for beers around 1.050 OG, I make a 1L starter from one Wyeast smack pack. If I am doing a greater than 1.050 beer I make a 2L starter. Both get around 48 hours in the starter and I chill, decant and then warm the starter before pitching. I usually do darker beers (brown ales, porters, stouts and whatnot, I haven't done any lighter beers like IPAs or other pale ales.)

    So my question is; Am I doing the right thing? I also use Beersmith 2 and enter in the recipe before I make a batch and see what it recommends in the yeast starter tab.

    Thanks!

    Reply
    • Hey Tony,

      That depends on the viability of the yeast!

      If you have, a 5 gallon batch of ale at 1.050 OG, you'll want about 173 billion cells. If you have a 2 month old pack of WYeast, you'll have about 62 billion viable cells (100 initial, 20%/month depreciation). If you make a one liter starter, you'll end up with about 200 billion cells which is more than enough! So you're good!

      However, take the same scenario, but now the yeast is 6 months old and the OG is 1.090. With a hybrid rate, you'd want 454 billion cells and you'd only have around 300 from a 2 liter starter.

      That said, you're working with a solid rule of thumb. It is always worth double checking and writing down the results so that you can ensure consistency!

      Reply
      • Thanks Matt.

        The problem I foresee is that some of the yeast I have gotten actually has an expiration date, not a manufactured date. Not a problem with Wyeast, but I have gotten some liquid yeast from my local store that did not have a manufacture date on it. However, I do try and steer away from those and stick to smack packs.

        So for hybrid for instance, would I make a 2L starter, cool/decant, and then add 2L more wort to raise the cell count? I ask because in a few months I am taking a stab at making Wil Wheaton's WootStout and I know that is a crazy high OG.

        Reply
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