Glossary · Microbiology
Lactic acid bacteria
Also written LAB. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
The bacteria that convert malic acid to lactic acid and, in other conditions, produce the disorders of ropiness, mousiness and acrolein bitterness. Oenococcus, Lactiplantibacillus and Lactobacillus species dominate in cider.
- Subject
- Microbiology
- Also written
- LAB
In more detail
The same organisms are responsible for the most valued and the most feared transformations in a cider cellar. What decides which happens is the substrate available and the conditions: malic acid at a sensible pH gives a clean conversion, while residual sugar, glycerol, sorbitol and citrate at high pH give off-flavours and slime.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Microbiology
Oenococcus oeni
The acid-tolerant lactic acid bacterium that carries out most deliberate malolactic fermentation, converting malic acid to lactic acid after the yeast has finished.
Microbiology
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Production
Malolactic fermentation
A bacterial conversion of sharp malic acid into softer lactic acid, which lowers acidity, changes aroma, and in most traditional cider happens whether it was planned or not.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Fermentation
Malolactic fermentation
The bacterial conversion of malic acid into lactic acid and carbon dioxide, which lowers total acidity, raises pH slightly and softens the drink. It is a bacterial process, not a yeast fermentation.
Microbiology
Oenococcus oeni
The lactic acid bacterium most used and most wanted for malolactic conversion, tolerant of low pH and moderate alcohol and, in the right conditions, reliably clean in what it produces.
Faults
Ropiness
A texture fault in which the cider becomes viscous and pours in an oily rope, caused by lactic acid bacteria producing extracellular glucan polysaccharide.
Sensory
Mousiness
A taint perceived only after swallowing, as a lingering flavour of mouse cage, stale popcorn or cracker, produced by tetrahydropyridines from lactic acid bacteria and *Brettanomyces*.
Chemistry
Acrolein
A pungent compound formed when certain lactic acid bacteria metabolise glycerol. Reacting with phenolics, it produces an intense and persistent bitterness known historically as *amertume*.
Faults
Framboise
A spoilage disorder in which lactic acid bacteria acting on phenolic compounds produce a strong raspberry-like aroma alongside a characteristic haze and loss of colour.
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.
The Science of Cidermaking and associated technical writing
Andrew Lea · reference work · passage verified 2026-08-24
Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.