I just pitched a whole 35mls vial of White Labs WLP001 California Ale Yeast into a 1 gallon batch of brown ale wort. I only intended to pitch half of the vial, but my brain turned off at exactly the wrong moment and I didn't stop myself.

I understand that pitching too much yeast can affect the flavor. Is there anything I can do to counteract the effect of excess yeast? Would lowering the fermentation temp help?

  • +1 for an interesting question. I don't have a definitive answer, so I'll just comment with my opinion: watch the temp, but I believe it should be fine. Here's a link to an article where someone tested pitching rates. Might be interesting.
    – JoeFish
    Jan 18, 2012 at 14:19
  • what was the packaging date or best before date on the vial?
    – mdma
    Jan 18, 2012 at 14:36
  • Best Before date on the vial is 2012.04.11. If White Labs dates 4 months from production then this is a very fresh batch. Jan 18, 2012 at 16:38

1 Answer 1


I think you will be fine. According to white labs:

White Labs Pitchable yeast is packaged with 70 to 140 billion yeast cells, which corresponds approximately to a 1-2 liter size starter. Lag times are typically between 12-24 hours for a normal strength brew.

For a 5 gallon brew with ale yeast 150 to 250 billion cells is normal, with up to 400 billion being ok without causing any problems (figures from the same page). Scaling that down to a 1 gallon brew, that's 30-50 billion cells, with 80 billion being a safe upper limit.

After 30 days in the vial, White labs say that yeast viability is down to 75-85% - ca. 50-100 million so we are already close to the safe pitching limit. If the vial was older still then I think there is no reason to worry.

Check the lag time - how long before active fermentation starts after pitching the yeast. If it's more than 5 hours then don't worry about it - the yeast will have needed to bud to increase the population, meaning that your pitching rates were fine to begin with.

If you feel you do need to compensate for over-pitching, you can do this by brewing the same type of wort again and add this to your existing ferment, after racking it to a larger vessel.

Although pitching too much yeast can cause off flavors, these are only ball-park figures - a little more a little less is fine in a homebrew setting. Good temperature control will have a much greater impact on flavor that the small overpitch that you may have here.

  • Thanks. I did the same math but the variability of the actual viability (50-100 million) in the vial still worried me. Jan 18, 2012 at 16:40
  • As of this morning (pitch +10 hours) there's no activity in the airlock. However, there is a lot of head space (1 gal in 2 gal bucket), so maybe pressure just hasn't built up yet. Trying my best with temp control, as it's cold and snowy here in Seattle right now; the bucket is in a chest cooler with a heating pad that I cycle on and off as necessary (wish I had a thermo controller). I'm aiming for 65F. Jan 18, 2012 at 16:51
  • Bottled this beer last night. OG 1.059/FG 1.016. Taste is good, though I'm no expert. Airlock bubbling was light during the first few days so I don't know what, if any, impact overpitching had. I'm pleased the final result came out well, anyway. (And I bought a thermo controller. ;) Feb 2, 2012 at 1:27

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