Fault
Gushing
Beer that erupts on opening, caused either by refermentation in the package or by fungal proteins from mould-affected barley.
Also called gushers, foaming over.
What it looks like
Gushing
Foam rises out of the bottle on opening and continues, without the beer having been poured. The cause is nucleation sites throughout the beer — usually a fungal infection of the malt, sometimes an infection in the bottle — so the carbon dioxide comes out everywhere at once rather than at the surface.
A vigorous pour
A large head produced by pouring hard down the middle of the glass. It is loose, it settles within a minute or two, and the beer underneath is unaffected. Pouring the same bottle gently gives a normal head.
What it tastes and smells like
Two quite different causes share this symptom. Primary gushing comes from hydrophobin proteins produced by Fusarium mould on the barley in the field, which nucleate bubbles violently; the brewer cannot fix it after the fact and often cannot detect it before packaging. Secondary gushing comes from continued fermentation in the package, whether from infection or from bottling too early.
Styles this tends to affect
Not where it belongs — where it is most likely to appear when something has gone wrong.
- American wild ale — A broad New World category of mixed-fermentation and barrel-aged sour beers, often fruited, with no fixed base style.
- Fruit lambic — Lambic refermented on whole fruit — traditionally sour cherry or raspberry — producing a dry, tart, intensely fruity beer.
- Gueuze — A blend of young and old lambic, refermented in bottle — intensely complex, bone dry and Champagne-like in its carbonation.
- Milkshake IPA — A hazy IPA with lactose and fruit added for sweetness and a fuller, creamier body.
- Pastry stout — A heavily adjuncted sweet stout built to taste like dessert, using lactose, vanilla, cocoa and similar additions.
- Saison — Dry, peppery and highly carbonated, with a bracing finish — the most refreshing thing strong beer does.
If you are drinking it
If a properly chilled, undisturbed bottle gushes, something is wrong with the beer and it is worth returning. Open suspect bottles cold and over a sink.
- Chill the bottle thoroughly and let it stand undisturbed before opening. (mitigates)
Not a safety issue. Beer’s alcohol, hop compounds and low pH make it inhospitable to organisms that cause illness.
What causes it
| Cause | Stage | How often | Who can act |
|---|---|---|---|
| Wild yeast or bacteria continuing to ferment residual sugars in a sealed package, steadily raising pressure. | packaging | most common | brewer |
| A warm or recently shaken bottle, which is a handling issue rather than a fault in the beer. | consumer storage | common | consumer |
| Fusarium infection of barley in the field producing hydrophobin proteins that survive malting and brewing and nucleate CO₂ aggressively. | raw materials | occasional | brewer |
If you are brewing it
- Brewer: Screen incoming malt for gushing potential and reject affected lots; there is no in-process fix. (prevents)
- Brewer: Confirm terminal gravity before packaging and maintain cold-side sanitation. (prevents)
Where in the process this comes from
Steps that can produce this fault when they go wrong. Each links to what the step is for and how it is controlled.
- Bottle conditioning — Carbonate beer through a secondary fermentation inside the sealed bottle, using residual or freshly-added yeast with priming sugar.
- Hop creep — Explain the renewed fermentation that dry hopping can start in beer that had already finished, and the over-carbonation and dryness that follow it.
- Priming — Add a measured quantity of fermentable sugar at packaging so residual yeast generates the intended carbonation in the container.
Often confused with
- Overcarbonation — excessive foam on pouring, sharp prickly carbonic bite
- Infection — unexpected sourness, barnyard
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.
Gushing-inducing hydrophobins are surface-active proteins that most filamentous fungi produce to grow across a liquid-air interface, and they reach the brewhouse when excessive fungal growth occurs on the grain either before harvest or in storage.
Checked against the source
Source: Bokulich & Bamforth, "The Microbiology of Malting and Brewing" (2013), Barley (Microbiol Mol Biol Rev 77(2):157–172)
Gushing has two unrelated causes: excess package pressure from continued fermentation, and hydrophobin proteins produced by Fusarium mould on barley in the field, which survive the entire brewing process.
Backed by a source
Sources: Brewing: Science and Practice — print; Journal of the Institute of Brewing