Cider science

Reading a juice analysis

What do the numbers on a juice analysis actually tell me?

In short

A full juice analysis answers three different questions, and the figures that answer each one are not the ones a beginner expects. Gravity answers how strong the cider will be. pH and nitrogen answer whether the ferment will go cleanly. Acid and tannin answer what it will taste like.

The most useful readings are pairs. Gravity alone is potential alcohol; gravity with acid is whether that alcohol will taste of anything. pH alone is a number; pH with titratable acidity tells you how well buffered the juice is. Nitrogen alone is a concentration; nitrogen against the gravity tells you whether there is enough of it for the amount of sugar the yeast has to get through.

Nothing on an analysis predicts a finished cider. What it does is tell a maker which decisions are still open and which have already been taken by the fruit.

Two juices reading pH 3.6 on the same meter, one carrying twice the titratable acidity of the other. Buffering is the reason, and it is why a cider maker measures both.

Described in full

Shape: Two panels side by side, each representing a juice. Each panel contains eight small squares in two rows, standing for units of acid: the left panel has four filled and four drawn in dashed outline, the right has all eight filled. Beneath each is its titratable acidity — 4.0 and 8.0 grams per litre. A single wide band below both, with arrows leading into it from each panel, states that both read pH 3.6.
What the squares count: Acid groups available to a titration. The titration finds every one of them, dissociated or not, because the alkali drives the equilibrium until all of them have reacted. That is what titratable acidity measures: how much acid is present.
What the meter finds: Only the hydrogen ions actually free in solution at that moment. Malic acid is a weak acid, so most of it sits undissociated at cider pH, and the free fraction is a small part of the total.
Buffering: The juice also contains the potassium salts of its own acids, and those salts absorb added hydrogen ions. A juice rich in potassium therefore holds a higher pH than its acid content alone would predict, which is how two juices with very different acid loads arrive at the same meter reading.
Why it matters: Perceived sourness follows the amount of acid; microbial risk and sulphite effectiveness follow pH. A maker who measures only one of the two is blind to whichever question the other answers, and the two questions have different answers on the same juice.

The figures, and what each one governs

What each juice measurement decides, and when the decision has to be taken.
Figure	What it governs	When it matters
Specific gravity or Brix	Potential alcohol, and body	Before pressing — it is fixed by the fruit and the ripeness
Titratable acidity	Perceived sharpness; whether the cider tastes of anything	At blending, when it can still be corrected
pH	Sulphite effectiveness, bacterial risk, protein stability	Before sulphiting, because the dose depends on it
Assimilable nitrogen	Whether the ferment finishes, and whether it makes sulphide	Before pitching — much easier than afterwards
Total phenolics or tannin	Bitterness, astringency, colour, ageing capacity	At blending
Sorbitol (perry)	Sweetness that will survive the ferment	Rarely measured; usually inferred
Pectin	Whether the juice will keeve, and whether it will clear	Before deciding on keeving or enzyme

Read gravity and acid together

A gravity of 1.055 means roughly 7 per cent potential alcohol, and that is all it means. Whether the resulting drink is worth making depends on what else is in the juice, and the figure that decides it most often is acid.

The Long Ashton bittersweets illustrate the problem. Dabinett at 0.18 per cent acid and Médaille d’Or at 0.27 will both ferment to a respectable strength and neither, alone, gives a drink with any lift to it. That is why the West Country tradition blends bittersweets with sharps rather than treating a high-gravity bittersweet as a complete cider. The exceptions — the fruit that carries acid and tannin at once — are the small group of vintage cultivars that single-variety cider is made from.

In the other direction, a sharp apple at 1.045 and 0.9 per cent acid gives a low-strength drink that tastes aggressive. Neither figure is a defect; the combination is.

Read pH and acid together

These two are not interchangeable and neither predicts the other, which is the single most consequential misunderstanding on a juice bench. Titratable acidity counts how much acid is present; pH measures how much of it is dissociated. Buffering — chiefly by the potassium salts of malic acid — decouples them, so two juices with the same acid load can sit at noticeably different pH values.

Which one to act on depends on what is being decided. If the question is whether the cider will taste flat, read the acid. If the question is what sulphite dose to use, read the pH: the molecular fraction of sulphur dioxide, which is the part that actually does the work, collapses as pH rises, and a dose calculated without the pH is a guess.

Read nitrogen against gravity, not on its own

The yeast has to convert all the sugar in the juice, and the nitrogen requirement scales with how much sugar that is. A hundred milligrams per litre of assimilable nitrogen is comfortable in a juice at 1.045 and marginal in one at 1.070, because the second juice asks the yeast to do half as much work again on the same ration.

Below roughly 100 milligrams per litre a cider ferment is generally expected to need thinking about, and the published work supports treating that as a prompt rather than as a threshold. The relationship between low nitrogen and hydrogen sulphide is real and it is not deterministic: studies find ferments at low nitrogen that produce little sulphide and ferments at adequate nitrogen that produce some, and the strain of yeast matters as much as the concentration.

In perry the question is sharper, because pear juice runs far lower and because a total amino acid figure flatters it badly. See the perry chemistry page for why.

The nuance CiderHQ keeps insisting on“Low nitrogen causes sulphide” is a tendency with documented exceptions, not a rule. Reported strongly enough, it leads a maker to add nutrient to a ferment that did not need it and to conclude that a sulphurous ferment was starved when the strain, the temperature or the sulphite regime may have done more.

What a single analysis cannot tell you

Whether the figure is typical for that fruit. One analysis is one juice from one parcel of fruit in one season. The National Association of Cider Makers compilation records Bramley three times at 1.21, 1.05 and 1.43 per cent acid — three readings of one cultivar, in one table, differing by more than a third.
How it will change. Acid falls as fruit ripens further, and it falls again if malolactic fermentation runs. Gravity moves if the fruit sweats before milling. An analysis is a snapshot of juice, not a property of the cultivar.
What the phenolic figure means for the palate. A total is a total: a juice with the same number can be bitter or astringent depending on the average chain length of its procyanidins, and no routine analysis reports that.
Anything about the finished cider. Fermentation temperature, yeast strain, oxygen management, lees contact and maturation all move the result more than the juice figures do.

Also answered on this page

Questions this page covers, so you can tell at a glance whether it is the one you want.

What should I measure in cider juice?
What is a good pH for cider juice?
How much nitrogen does cider juice need?
What gravity should cider juice be?
Does a juice analysis predict the finished cider?

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 know when my cider has finished fermenting — Take two hydrometer readings several days apart: if the gravity has not moved, the ferment is over. Airlock activity is not a reliable test, because a slow ferment can produce gas too slowly to see.
What is apple juice actually made of — By mass, apple juice is around 85–90% water. Most of the rest is sugar — fructose predominantly, with glucose and sucrose — and it is that sugar which sets how much alcohol the juice can produce.
What is the difference between perry and cider — Perry is fermented pear juice and cider is fermented apple juice, and four chemical differences follow: pear juice carries sorbitol that will not ferment, citric acid that apple juice lacks, much less usable nitrogen, and tannin that reads as drying grip rather than as bitterness.
How much acid should cider have — Commonly quoted targets sit around 4 to 6 grams per litre as malic acid, but acid and pH are separate questions and neither predicts the other. Perceived sharpness follows the acid; microbial risk and sulphite effectiveness follow the pH.
What proportions of apples should i blend — There is no universal ratio, and CiderHQ does not publish one as if there were. A common West Country starting point is a majority of bittersweet fruit with enough sharp fruit to bring the pH down and the acid up.
Why do cider makers add sulphite, and how much

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.
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.
Characterization of Malus Genotypes within the USDA-PGRU Malus Germplasm Collection for their Potential Use within the Hard Cider Industry
Cornell University / USDA-ARS Plant Genetic Resources Unit · university · passage verified 2026-08-25 · covers 2017 harvest
A Cornell masters thesis, open access, read in full on 2026-08-25 including the supplemental tables. The largest single-season cider characterisation CiderHQ holds: 158 accessions from the United States national apple collection, each measured for fruit weight and diameter, starch pattern index, firmness, soluble solids, titratable acidity, pH, total phenolics and the four sugars separately. Every mean is published with its standard deviation, which is why CiderHQ can store dispersion here and cannot for most historic tables. Forty-seven of the accessions correspond to cultivars the site already holds; the figures are transcribed for those and the accession identifier is recorded against each, because a germplasm label is a claim about identity rather than a proof of one.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
Perry Pears and Perry — Research and Survey Work
Cider and Perry Academy (Peter Mitchell) · specialist publication · passage verified 2026-08-25 · covers 2022–2024
Ongoing survey work by a cider and perry technologist who has taught production for decades, published openly and updated annually; retrieved and read in full on 2026-08-25. Thirty-eight single-variety perry pear juices analysed for gravity, titratable acidity, the tannin and phenolic acid fractions separately, and the individual amino acids by HPLC — the last of which nobody else has done at this scale for perry. Not peer-reviewed, and the author is explicit that the accompanying fermentation trials are initial surveys needing statistical treatment before differences are called significant; CiderHQ repeats that wherever the fermentation results are used.