species
Lactobacillus
Lactic acid bacteria that produce clean sourness — essential to Berliner Weisse, gose and kettle souring, and ruinous elsewhere.
Lactobacillus converts sugars to lactic acid, giving a clean, sharp sourness without the vinegary edge of acetic acid. It works fast at warm temperatures, which is what makes kettle souring practical on a timescale of hours rather than months.
Most strains are strongly inhibited by hops, which is why traditional sour styles are very lightly hopped and why kettle souring happens before the boil.
Behaviour
| Scientific name | Lactobacillus spp. |
|---|---|
| Fermentation temperature | 30–45°C |
| Esters | none |
| Phenols | none |
Used in
- Berliner Weisse
A very low-strength sour wheat beer: sharply lactic, bone dry, lightly sparkling and enormously refreshing.
- Gose
A lightly sour German wheat beer with added salt and coriander — tart, savoury and unusually thirst-quenching.
- Lambic
Spontaneously fermented Belgian wheat beer, matured in oak for years — funky, acidic, dry and unlike any other beer.
- Flanders red ale
A deep red sour ale matured for years in oak foeders, balancing sharp acidity against dark fruit and a vinous depth.
- Oud Bruin
An East Flanders aged brown ale, maltier and less sharply acidic than Flanders red, with raisin and caramel depth.
- American wild ale
A broad New World category of mixed-fermentation and barrel-aged sour beers, often fruited, with no fixed base style.
- Kettle sour
Beer soured with Lactobacillus in the kettle over hours rather than months, then boiled and fermented normally — usually fruited.
- Lichtenhainer
A historical Thuringian smoked wheat beer that is also lightly sour — an unusual combination of smoke and lactic acidity.
- Kentucky Common
A quick-turnaround dark American beer brewed largely from maize, often lightly soured, extinct since Prohibition.
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.
Many Lactobacillus strains are inhibited by hop iso-alpha-acids, which is why kettle souring is performed before the hop addition and why heavily-hopped beer resists lactic spoilage.
Backed by a source
Sources: Yeast: The Practical Guide to Beer Fermentation — print; Brewing: Science and Practice — print