Sensory descriptor
Cheesy
A rancid, sweaty note from short-chain fatty acids, chiefly butyric and isovaleric, produced by bacteria.
Also called Sweaty, Rancid, Old cheese.
- Aroma family
- Dairy and lactic
- Does it indicate a fault?
- It depends on the style it is met in
What causes it
Butyric acid smells of rancid butter and vomit; isovaleric acid smells of stale cheese and sweat; both have very low thresholds. In cider they come from bacterial metabolism — Clostridium species producing butyric acid from lactate or from sugars under low-oxygen conditions, and a range of bacteria and yeasts producing isovaleric acid from leucine. Brettanomyces is a notable isovaleric acid producer, which is why cheesy notes so often accompany the phenolic family. The conditions that favour them are the same ones that favour every other bacterial fault: low sulphite, higher pH and long standing.
There is no level at which butyric acid is acceptable. Isovaleric acid at trace level is part of the farmyard composite in traditional cider; where it can be identified independently as cheese, it has gone beyond that.
The compounds responsible
Where the molecule is established. Some descriptors in this lexicon name a compound the compound register does not yet hold a record for; those are named in the cause above instead.
Lactic acid
The softer acid that replaces malic when malolactic fermentation runs, halving the acid a cider carries and changing its texture as much as its sharpness.
Amino acids
The largest usable nitrogen fraction in apple juice, and the raw material from which yeast builds both its own protein and most of the aroma compounds a cider carries.
Biogenic amines
Amines produced when bacteria decarboxylate amino acids, associated with long lees contact at high pH and low sulphite, and a reason bacterial activity is managed rather than simply tolerated.
The organisms that make it
Where a specific organism is implicated rather than the fruit. Naming one answers a different question from naming a molecule: what is in the cellar, rather than what is in the glass.
Pediococcus species
Homofermentative lactic acid bacteria that grow in tetrads, associated in cider with ropiness, diacetyl and slow spoilage during maturation.
Lactobacillus brevis
An obligately heterofermentative lactic acid bacterium, renamed *Levilactobacillus* in 2020, associated with volatile acidity, biogenic amines and mousiness rather than with clean malolactic conversion.
What raises it
Processes that increase this character, or preserve it where it would otherwise be lost.
Sulphite stabilisation
Managing free sulphur dioxide through maturation and at packaging so that a useful antimicrobial and antioxidant fraction survives into the bottle.
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Racking
Moving cider off the sediment it has thrown, which both cleans the liquid and — by taking yeast and nitrogen away with the deposit — slows what is left of the ferment.
Acid adjustment
Correcting the acidity of low-acid juice before fermentation, usually with malic acid, and the difference between the pH question and the titratable acidity question.
The fault it points at
Meeting this descriptor above a certain intensity is how the fault below is usually noticed first.
Fault
Sauerkraut, sour milk, silage or cheesy notes from lactic acid bacteria working on sugars and other substrates rather than on malic acid alone.
About Cheesy
Cheesy notes point at a pH problem more often than at anything else. Cider from low-acid bittersweet fruit can sit above pH 4, where the bacteria responsible are far more comfortable, and acid adjustment is the standard preventive measure.
The descriptor overlaps with horse blanket in the phenolic family, since isovaleric acid contributes to both, and the two should be recorded together where both are present.
Others in the dairy and lactic family
Butter, butterscotch, yoghurt, cream.
Butter
The buttery note of diacetyl, produced by lactic acid bacteria during malolactic conversion.
Butterscotch
Diacetyl at higher concentration with a caramel edge, sitting at the boundary between character and fault.
Cream
A soft, rounded dairy impression from acetoin and lactic acid without the sharpness of free diacetyl.
Soured milk
A sharp, unclean dairy note from uncontrolled lactic activity, recorded as a fault in every style.
Yoghurt
A tangy fermented-dairy note from lactic acid with acetaldehyde, indicating vigorous bacterial activity.
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- What is racking in cider making — Racking is siphoning cider off the sediment it has thrown into a clean vessel, leaving the lees behind. It clarifies the cider and, in traditional practice, is also used to slow a ferment by removing yeast with the lees.
- Why does cider contain lactic acid — Because malolactic bacteria converted the malic acid into it. Malic acid has two acid groups and lactic acid has one, so roughly half the titratable acidity disappears and the cider tastes softer.
- How do you adjust the acidity of cider
- Does cider contain histamine — Cider can contain biogenic amines including histamine, formed mainly by lactic acid bacteria after fermentation. Levels vary widely and are higher where malolactic activity has been extensive.
- What is pediococcus and what does it do to cider — A lactic acid bacterium associated with ropiness, diacetyl and, in some conditions, mousiness. It is more of a problem at higher pH, which is one more reason low-acid juice is the harder juice to keep.
Where to go next
- The sensory model — The thirteen structural dimensions and the twenty aroma families, in full.
- Compounds — The chemistry behind the words.
- Troubleshooting — When a perception turns out to be a problem, this is where it is diagnosed.
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.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.