Compound
Ethyl lactate
The slow-forming ester of lactic acid and ethanol, which accumulates after malolactic fermentation and contributes the soft, milky roundness of a long-matured traditional cider.
- Class
- Esters
- Formula
- C5H10O3
- How often it matters
- Occasional
What it does in cider
- Forms chemically rather than enzymatically, by slow esterification of lactic acid with ethanol during maturation.
- Requires lactic acid to be present, so it is effectively a marker that malolactic fermentation has occurred.
- Contributes softness and a creamy, milky quality rather than a distinct aroma, at concentrations far higher than the fruit esters need.
- Continues to build in the bottle, so it is one of the few flavour compounds that increases with age.
How it is perceived
What the compound registers as, and at roughly what concentration. Perception is not a property of the molecule alone: sugar, tannin and carbonation all change where a threshold falls.
- milky
- creamy
- soft
- buttery-adjacent
A high-threshold compound compared with the fruit esters, needing concentrations in the tens to hundreds of milligrams per litre before it registers — which is why it appears only in ciders that have been through malolactic and then given time.
Descriptors it is responsible for
Sensory records that name Ethyl lactate as a cause. Each states the perception and the mechanism behind it.
- Cream — A soft, rounded dairy impression from acetoin and lactic acid without the sharpness of free diacetyl.
The structure it moves
| Dimension | What it is |
|---|---|
| Body | How much weight and viscosity the drink has in the mouth. |
| Fermentation character | Aromas made by the ferment rather than carried in from the fruit. |
| Acidity | The sharp, mouth-watering quality that makes a cider taste fresh rather than flat. |
Measured figures
Shown as they were measured, with the context each was taken in. They are not averaged: a concentration recorded in one country's fruit in one decade is not a constant.
Aroma detection threshold14.0 mg/L
context not recorded · Odour detection threshold quoted in a cider sensory study, stated as approximately 14 mg/L · Chen, Zhao, Jiang, Liu, Cao, Ye, Mao and He, Foods 14(6):1005
A high threshold, and that is the point of recording it. Ethyl lactate is one of the more abundant esters in a cider that has been through malolactic fermentation and is nevertheless among the least perceptible, because a nose needs milligrams of it where ethyl acetate needs a fraction of that and β-damascenone needs nanograms. Abundance and importance are different questions.
The concentration at which a compound becomes perceptible — which is why a trace compound can matter more than an abundant one. Measured in milligrams per litre.
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
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.
Tank maturation
Resting cider in stainless steel or a lined vessel, where the point of the container is that it contributes nothing and admits almost no oxygen.
Bottle maturation
What happens to a cider after it is sealed in glass — which for most ciders is slow decline rather than improvement, and saying so is more useful than implying otherwise.
Lees ageing
Deliberately holding a cider or perry on its fine yeast deposit so that autolysing cells release material that changes texture and foam behaviour.
Faults it is implicated in
Being implicated is not the same as being a fault. Several of the compounds on this site are ordinary constituents of a sound cider and define a named fault only above a concentration.
Organisms that produce it
Which organism is responsible usually decides whether the compound is a feature or a symptom.
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.
Lactiplantibacillus plantarum
A versatile lactic acid bacterium, renamed out of *Lactobacillus* in 2020, capable of malolactic conversion and of a range of faults depending on conditions.
About Ethyl lactate
Most of the esters in cider are made by yeast in a matter of days. Ethyl lactate is not: it forms by ordinary acid-catalysed esterification between lactic acid and ethanol, a reaction slow enough that it takes months to years to reach concentrations that matter. It therefore accumulates on a different timescale from everything else, rising while the fruit esters are hydrolysing away.
Because it needs lactic acid, its presence says something specific: this cider went through malolactic fermentation, and then it sat. It is one of the reliable chemical markers of the traditional West Country and Normandy maturation regime, and it is almost absent from a fresh, sterile-filtered, malolactic-free cider however long that cider is kept.
Sensorially it is undemonstrative — a soft milkiness that rounds the mid-palate and slightly blunts the impression of acidity. In combination with diacetyl and the general softening of tannin over time, it is a substantial part of what people mean when they say an old farmhouse cider tastes mellow.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Acids
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.
Ketones
Diacetyl
The butter compound, made mainly by lactic acid bacteria and perceptible at very low concentration, which is a defining part of some traditional ciders and an obvious fault in others.
Ketones
Acetoin
The intermediate between diacetyl and odourless 2,3-butanediol, far less aromatic than the compound it comes from and a useful marker of how far lactic and acetic activity has run.
Acids
Malic acid
The acid of apples, which supplies almost all the sharpness a cider has and, through pH, decides how vulnerable that cider is to everything that could spoil it.
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.
- What is malic acid and why does it matter in cider — Malic acid is the acid of apples and supplies almost all the sharpness a cider has. It also sets pH, which decides how well sulphite works and how exposed the cider is to spoilage, so it does far more work than its taste suggests.
- 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.
- Which bacterium carries out malolactic fermentation in cider — Oenococcus oeni, in cider as in wine. Genome studies find that the cider strains are genetically distinguishable from the wine ones and that the strain most basal to the whole species was isolated from cider.
- Does cider get better with age — Some does. Tannic, dry, bottle-conditioned ciders and ice ciders can gain for several years. Light, fruit-driven and commercially filtered ciders lose their aroma and do not gain anything in exchange.
- What is malolactic fermentation — Malolactic fermentation is a bacterial conversion of sharp malic acid into softer lactic acid, releasing carbon dioxide. It lowers total acidity and raises pH, and in cider it is often the source of a farmyard or buttery note as well.
- What is lactiplantibacillus plantarum doing in cider
Where to go next
- All compounds — Grouped by what the fruit brings and what the ferment makes of it.
- Sensory — Every descriptor, with the compound or process that causes it.
- Microbiology — The organisms whose metabolism most of this chemistry belongs to.
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.
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.
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.