Compound
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.
Also called L-malic acid, Apple acid.
- Class
- Acids
- Formula
- C4H6O5
- How often it matters
- Present in every cider
What it does in cider
- Provides the overwhelming majority of the acidity in apple juice, and is the acid every conventional total-acid figure is reported as.
- Sets pH, and pH governs microbial risk, sulphite effectiveness and enzyme activity — so the acid does far more work than its taste suggests.
- Suppresses the perception of sweetness, so the same residual sugar tastes drier in a sharp cider than in a low-acid one.
- Falls as fruit ripens and falls further in a warm season, which is why the same cultivar can classify differently in two climates.
- Is converted to lactic acid by malolactic bacteria, halving its acidic contribution and raising pH — the single largest deliberate change a maker can make to acid balance after pressing.
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.
- sharp
- green apple
- mouth-watering
- crisp
- lingering sourness
Perceived sourness tracks titratable acidity far more closely than pH. Two ciders at the same pH can taste markedly different in sharpness, and malic acid is described as harder and more persistent than lactic acid at equal acidity.
Descriptors it is responsible for
Sensory records that name Malic acid as a cause. Each states the perception and the mechanism behind it.
- Bittersweet apple — The soft, low-acid, faintly earthy ripe-fruit character of traditional West Country cider fruit, inseparable from its phenolic weight.
- Fresh pear — Clean, watery, faintly green pear aroma, the base fruit note of perry and of pear-fruited cider.
- Green apple — A harder, sharper apple note than fresh-cut apple, driven by (E)-2-hexenal and reinforced by high malic acid.
- Dessert apple — The bright, aromatic, low-tannin fruit character of eating apples, dominant in eastern counties and most modern mainstream cider.
- Lemon — A sharp citrus impression built from high malic acid read alongside light esters and terpene traces.
- Sweet apple — An impression of sweet fruit produced by aroma rather than by sugar, common in dry ciders with a high ester load and low acidity.
- Citrus pith — A dry, bitter citrus note where phenolic bitterness sits alongside sharp acidity rather than behind fruit.
- Crab apple — A small-fruit character combining very high acidity, hard green aldehydes and a marked phenolic grip.
- Flat and lifeless — The absence of aroma and lift where both were intended — a fault defined by what is missing rather than present.
- Unripe apple — A hard, starchy, low-aroma character from fruit milled before the climacteric, with acid high and esters not yet formed.
- Unripe pear — Hard, green, markedly astringent pear character from fruit pressed before it softened.
- Wet stone — A cool, damp, faintly mineral impression, in cider a product of low-level sulphur compounds and high acidity rather than of minerals.
- Apple sauce — Cooked culinary-apple character with the sharpness retained, met where high-acid fruit has been heat-treated.
- Lime — A green, zesty citrus impression from very high malic acidity combined with the green aldehyde fraction.
- Melon — A soft, watery, faintly green tropical note from hexyl esters and residual nine-carbon aldehydes.
The structure it moves
| Dimension | What it is |
|---|---|
| Acidity | The sharp, mouth-watering quality that makes a cider taste fresh rather than flat. |
| Freshness | Whether the drink smells and tastes of live fruit or of time and air. |
| Sweetness | How sweet the drink tastes, which is not the same as how much sugar it contains. |
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.
3 separate analyses of malic acid. They are shown as they were measured, in their own contexts, and are not averaged — the same fruit grown somewhere else can genuinely give a different number.
Malic acid0.200–1.000 % w/v
Long Ashton, Somerset, England, 1903–2003 · Titration, reported as malic acid · National Fruit and Cider Institute / University of Bristol
Historic analyses of fruit grown at one site in one climate. The band spans everything from low-acid bittersweets near the bottom to sharp culinary fruit near the top; a single cultivar’s figure varies between seasons and shifts when the tree is grown somewhere warmer.
Malic acid0.450 % w/v
context not recorded · Long Ashton classification threshold · National Fruit and Cider Institute / University of Bristol
A dividing line, not a measurement of anything. Fruit above it is classed sharp or bittersharp and fruit below it sweet or bittersweet. The same figure is 4.5 g/L in modern units; nothing physical happens at the boundary, and cultivars sitting close to it are placed differently by different sources in good faith.
Malic acid0.0–0.5 g/L
Villaviciosa, Asturias, Spain, 2001–2002 · 4 samples · HPLC; the paper reports the result as “lower than 0.5 g/l” without a figure · Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31
What is left of the fruit’s own acid after a complete malolactic fermentation on the indigenous flora. The upper bound is the paper’s own wording rather than a measured maximum, and the lower bound is CiderHQ’s, not the study’s. In the same ciders lactic acid stood at 4.0–4.7 g/L — the malic acid did not disappear, it changed identity.
The dominant acid in apple and pear juice, and the one that tastes sharp. Measured in percent weight per volume.
pH3.20–4.00 pH
context not recorded · Andrew Lea
Acid strength, not acid quantity, and the two do not move together in the way intuition suggests. Sharp juices sit at the low end; low-acid bittersweets routinely sit at 3.8 or above, which is high enough that sulphite becomes weak and spoilage bacteria become comfortable.
Acid strength, which governs microbial risk and sulphite effectiveness. Measured in ph.
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
Ripeness assessment
Judging when cider fruit has converted enough starch, loosened enough on the spur and hardened enough for the store to be worth gathering.
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.
Acid balancing
Bringing a cider to the sharpness it needs, which requires separating perceived sharpness from titratable acidity from pH — three related things that do not move together.
Juice blending
Combining juices from different cultivars before fermentation so that the blend ferments as a single batch, as against fermenting separately and blending later.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
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.
Blending
Combining separate lots of cider or perry into one, which in cider is the historically normal way of making the drink rather than a remedy applied when single lots disappoint.
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.
Excessive acidity
Acidity high enough to dominate everything else, leaving a cider that is thin, hard and sour rather than fresh.
Low acidity
A cider without enough acid to give it definition, tasting soft, heavy and dull — and sitting at a pH that leaves it exposed to spoilage organisms.
Lactic off-flavours
Sauerkraut, sour milk, silage or cheesy notes from lactic acid bacteria working on sugars and other substrates rather than on malic acid alone.
Volatile acidity
The measurable fraction of acidity that can be steam-distilled off, dominated by acetic acid and read as vinegar sharpness in the nose and a hard, hot finish.
Film yeast growth
A pale, powdery or wrinkled film of aerobic yeast growing on the surface of a standing cider, consuming alcohol and acid and producing acetaldehyde.
Excess diacetyl
A butter, butterscotch or popcorn character from diacetyl, produced by lactic acid bacteria metabolising citric acid, and by yeast under stress.
Flat and lifeless
A cider with nothing obviously wrong and nothing to say: aroma faded, acidity dulled, finish short — usually the cumulative result of over-processing or slow oxidation.
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.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Schizosaccharomyces pombe
A fission yeast that degrades malic acid to ethanol rather than to lactic acid, offering deacidification without bacteria at the cost of a real risk of off-flavours.
Described in full
- Two axes, not one
- The upper scale is pH, running from 4.2 on the left down to 3.2 on the right. The lower scale is titratable acidity in grams per litre as malic acid, running from two to ten. They measure different things and are drawn separately for that reason.
- What pH measures
- The concentration of free hydrogen ions — the strength of the acid actually dissociated at that moment. It governs microbial risk, the effectiveness of sulphite, and how stable the cider is. It is a logarithmic scale, so a change of 0.3 is a doubling.
- What titratable acidity measures
- The total amount of acid present, found by neutralising it with alkali. It tracks perceived sourness far more closely than pH does, and it is what a taster responds to.
- The V on the figure
- Two juices are marked at the same pH on the upper scale. Lines run down to two clearly different positions on the acidity scale below. Same pH, different acidity, and they would not taste alike.
- Why they come apart
- Potassium and other cations in the juice buffer it. A juice rich in potassium holds its pH up while carrying a lot of acid, so a high-acid fruit can arrive at a pH that offers less protection than its sourness suggests.
- The practical consequence
- A cidermaker needs both numbers. Blending to taste uses titratable acidity; deciding on a sulphite addition, or whether a juice is safe to ferment slowly, uses pH. Neither substitutes for the other.
- Typical territory
- Bittersweet juice sits at the low-acidity, high-pH end and is the most vulnerable to spoilage. Sharp fruit is added to blends as much to bring pH down as to make the drink taste fresher.
About Malic acid
Roughly nine parts in ten of the acid in apple juice is malic acid, and the rest is mostly quinic and citric. It is a dicarboxylic acid — two acid groups on a four-carbon backbone — which is why it punches above its weight both in titration and on the tongue. Every conventional acid figure in cider, whether written as 0.6% w/v or as 6 g/L, is a titration result expressed as though all the acid present were malic. That convention is old, it is universal, and it is worth knowing because it means an acid figure measures quantity, not identity.
The distinction that causes the most trouble is between titratable acidity and pH. Titratable acidity counts how much acid is there; pH measures how strongly it dissociates in the particular mixture of salts and buffers the juice happens to contain. They correlate loosely and diverge often, and the divergence matters because they govern different things. Sourness on the palate follows titratable acidity. Microbial safety, sulphite efficacy, enzyme behaviour and colour stability follow pH. A juice can be respectably acidic to taste and still sit at a pH where sulphur dioxide barely functions.
This is the central problem of traditional English and French cider fruit. Bittersweet apples are defined by low acid, and low acid means high pH — commonly 3.8 or above, occasionally over 4.0. At that pH the molecular fraction of sulphur dioxide collapses to around one per cent of the free SO2, lactic bacteria find conditions congenial, and the ferment is exposed. The traditional answer is not a chemical one but a blending one: a proportion of sharp fruit in the blend brings pH down to somewhere defensible, and that is a large part of what sharps are for. Adding malic or citric acid directly is possible and is done, but it corrects the number more readily than the taste.
Malic acid is also the one major acid a maker can deliberately remove. Malolactic bacteria decarboxylate malate to lactate, turning a two-acid molecule into a one-acid molecule; roughly half the titratable acidity disappears and the pH rises by a couple of tenths. The cider becomes softer and rounder, gains whatever lactic and diacetyl character the organism brings with it, and loses some of its edge. In much of traditional West Country and Normandy cider this happens as a matter of course and is part of the style; in a cider built on freshness it is a loss, and the way to prevent it is to keep the pH low, keep sulphite adequate and rack the cider off its lees before the bacteria get going.
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.
Acids
Quinic acid
The second acid of apple juice, better known as the part of chlorogenic acid that is not caffeic acid, and a small but real contributor to the astringent grip of cider fruit.
Acids
Citric acid
A minor acid in apples and a much more significant one in pears, whose metabolism by lactic bacteria is the reason perry gains more butter and more vinegar from malolactic fermentation than cider does.
Acids
Succinic acid
An acid made by the yeast rather than the fruit, which adds a salty-bitter edge to a dry cider and, unlike malic acid, cannot be removed by malolactic fermentation.
Additives and processing aids
Sulphur dioxide
The antimicrobial and antioxidant on which most modern cidermaking depends, and whose effectiveness collapses as pH rises — which makes every sulphiting decision a pH decision first.
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.
- Does cider contain sulphites — Most does. Sulphur dioxide is added to protect juice and finished cider, and fermentation itself produces a small amount even when none is added. European labels must declare it above 10 mg per litre.
- Can you fix a cider that has gone vinegary — Not really. Volatile acidity cannot be removed at small scale, and blending it away only dilutes it. The realistic options are to accept it, to blend a lightly affected batch into a much larger sound one, or to let it finish becoming vinegar.
- 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.
- How do i balance acid and tannin in a blend — Acid and tannin do different jobs and cannot substitute for each other: acid gives freshness and microbiological safety, tannin gives structure and length. A blend short of acid tastes flabby however tannic it is.
- How do you blend 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.
Long Ashton Research Station cider fruit analyses
National Fruit and Cider Institute / University of Bristol · research institute · registered as competent for this subject · covers 1903–2003
The foundational body of cider-fruit science in English. Long Ashton produced the acid-and-tannin classification that divides cider apples into sweet, sharp, bittersweet and bittersharp, and analysed hundreds of cultivars grown at its Somerset site. Its figures are historic measurements of specific fruit at a specific place, not universal constants — a distinction CiderHQ preserves in every measurement record that cites it.
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.
A Somerset Pomona: The Cider Apples of Somerset
Liz Copas, The Dovecote Press, 2001. ISBN 9781874336877 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against Open Library: Liz Copas, The Dovecote Press, 2001, ISBN 9781874336877. The author was Long Ashton’s cider pomologist, which is why this work is registered for Somerset cultivar identity at all — it is the nearest thing to a successor to the station’s own descriptions. No copy was opened. Not digitised in any open collection.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.
Institut Français des Productions Cidricoles (IFPC)
IFPC · research institute · retrieved 2026-08-24
The French technical institute for cider production. The authority for the French cultivar classification families, for keeving as an industrial process, and for the pectin and nitrogen chemistry that keeving depends on.