Glossary · Faults
Mother of vinegar
Also written mother, vinegar mother. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
The gelatinous cellulose mat produced by acetic acid bacteria at a liquid surface. In a vinegar barrel it is the working culture; in a cider cask it is proof that the batch is being lost.
- Subject
- Faults
- Also written
- mother, vinegar mother
In more detail
The mat is bacterial cellulose secreted by Komagataeibacter and related genera, which holds the bacteria at the air-liquid interface where the oxygen is. It should not be confused with a film yeast, which is thin, dry-looking and powdery rather than rubbery and thick.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Microbiology
Komagataeibacter species
Highly acetic-acid-tolerant bacteria that build the cellulose pellicle known as mother of vinegar, and the organisms of industrial vinegar fermentation.
Style
Cider vinegar
Not a cider but its next stage: cider whose ethanol has been oxidised to acetic acid by bacteria, made deliberately as a condiment and arrived at accidentally as a fault.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Faults
Acetification
The oxidation of ethanol to acetic acid by acetic acid bacteria, turning cider progressively into vinegar. It requires oxygen and is the classic fault of a slack, part-empty cask.
Microbiology
Acetic acid bacteria
Aerobic bacteria — *Acetobacter*, *Gluconobacter* and *Komagataeibacter* — that oxidise ethanol to acetic acid. They require oxygen, which is why they colonise surfaces, ullage and slack fittings.
Faults
Film yeast
Aerobic yeasts, chiefly *Pichia* and *Candida* species, that grow as a dull white or grey film on the surface of cider in a part-empty vessel, metabolising ethanol and acids.
Cider
Cider vinegar
Cider whose ethanol has been oxidised to acetic acid by acetic acid bacteria, producing a vinegar of about 5 per cent acidity. In a cider house the same process, unwanted, is a fault.
Fermentation
Ullage
The empty space between the surface of the cider and the top of its container, and by extension the volume lost that creates it. Ullage in a maturing cask is where oxidation and acetification start.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.