fermentation
Pitching
Add yeast to cooled, oxygenated wort at a rate matched to the volume, gravity and fermentation temperature.
What is actually happening
Pitching rate governs how much the yeast has to reproduce before it can start fermenting. Under-pitching forces extra growth cycles, and growth is when yeast produces most of its esters, fusel alcohols and diacetyl precursor.
Lagers are conventionally pitched at roughly double the ale rate, because cold fermentation gives the population much less opportunity to multiply.
Over-pitching is a real error too, though a rarer one: too little growth produces a thin, characterless beer that finished before it developed anything.
Typical conditions
| Temperature | 8–22°C |
|---|---|
| Scale | Used at both homebrew and commercial scale |
Ranges, not targets. These describe what is usual across the styles and breweries that use this step, and a value outside the range is a decision rather than an error.
What goes wrong here
Risks rather than certainties. This step does not cause these faults; getting it wrong can.
- Stalled fermentation — Fermentation stopping well short of terminal gravity — leaving a sweet, underdeveloped beer and a package-pressure risk.
- Fusel alcohol — Harsh, solvent-like alcohol heat from fermentation run too warm or under stress — distinct from the pleasant warmth of a strong beer.
- Diacetyl — A buttery compound with a very low threshold — normally a sign of rushed fermentation, but traditional at trace levels in some Czech lagers.
Related steps and concepts
- Wort oxygenation — What must happen immediately before.
- Primary fermentation — What pitching starts.
- Lag phase — The period that follows.
Also at the fermentation stage
Biotransformation · Bottom fermentation · Diacetyl rest · High-gravity brewing · Hop creep · Mixed fermentation · Open fermentation · Pressure fermentation · Primary fermentation · Spontaneous fermentation · Top fermentation · Yeast harvesting
See the whole process in order on how beer is made.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Lagers are conventionally pitched at roughly twice the cell density used for ales, because cold fermentation gives the yeast population much less opportunity to multiply.
Backed by a source
Sources: Yeast: The Practical Guide to Beer Fermentation — print; Technology Brewing and Malting — print
Pitching rate shapes flavour as well as speed: under-pitching forces additional growth cycles, and yeast growth is when most esters, fusel alcohols and diacetyl precursor are produced.
Backed by a source
Source: Yeast: The Practical Guide to Beer Fermentation — print