Biga
A stiff Italian pre-ferment, drier than a poolish, giving a firmer dough and a more restrained, less acidic character.
A biga is the stiff counterpart to a poolish, conventionally somewhere near 50–60% hydration, and like a poolish it is built with commercial yeast for a single bake. The lower water content slows enzymic and microbial activity, so a biga ferments more slowly than a poolish with the same yeast quantity and develops a different, generally milder and more acetic profile.
The practical consequence is dough strength. Where a poolish increases extensibility, a biga tends to produce a firmer, more elastic final dough, which is why it is associated with breads that need to hold an open structure without slackening.
When to throw it away
As for a poolish: a single-use commercial-yeast ferment with no maintenance questions. Discard rather than use if fuzzy or coloured growth appears.
What is living in it
Microbiology
Commercial baker’s yeast in a low-water environment, with a smaller bacterial contribution than a slack pre-ferment of the same age because less free water limits microbial activity.
Directional and mechanistic. The comparison with poolish is the substance of the claim; no absolute figures are asserted.
RecordedEstablished practice, not a measured result
Hydration
Typical hydration
45–65% (typically 55%)
Ranges given for a biga vary between authors and regions. Recorded as a range with a typical value rather than as a definition.
RecordedEstablished practice, not a measured result
How it is kept
Built for one bake
Like a poolish, a biga is used entirely. Its distinguishing variable is hydration rather than schedule.
Definitional rather than a claim about the world.
RecordedTrue by definition rather than by measurement
How to tell it is ready
These are observations, not a schedule. Time to peak depends on temperature, refreshment ratio and flour, and those interact — so the clock tells you roughly when to look, and the list below tells you what you are looking for.
- Sign 1
- Roughly doubled and visibly aerated when torn open, rather than domed — a stiff pre-ferment does not dome the way a slack one does.
- Sign 2
- Tears to reveal a web of small cells rather than large irregular holes.
- Sign 3
- Smells faintly sour and nutty rather than winey.
Related
Built and refreshed from
As with a poolish. The difference between the two is hydration, not organism.