Ask Mr. Wizard

Too Much Yeast? Is over-pitching a problem?

TroubleShooting

Jon K. Rodrigo — Manila, Arkansas asks,
Q

It seems like I often hear about the “dire” effects from under-pitching yeast, but can’t say I’ve heard much about the consequences of over-pitching, besides the advice of: “Don’t do it.” Would love to hear what problems are associated with over-pitching yeast, notably over-pitching with yeast slurry?

A
Averbelen et al. (Impact of Pitching Rate on Yeast Fermentation Performance and Beer Flavour, Applied Microbiology Biotechnology (2009) 82:155–167) demonstrated that increasing pitching rates of lager yeast from 10 to 120 million
Response by Ashton Lewis.