Equipment
The pH meter and its calibration
Do I need a pH meter for cider, and how do I keep it accurate?
In short
A pH meter consists of a glass electrode that develops a small voltage proportional to hydrogen ion activity, a reference electrode, and a meter that converts that voltage into a pH reading.
pH matters in cider for two reasons that have nothing to do with taste. It determines which spoilage organisms can grow, and it determines what fraction of any added sulphur dioxide exists in the molecular form that actually does the antimicrobial work.
The instrument is only as good as its last calibration. An uncalibrated meter gives a confident number that may be wrong by enough to change a decision entirely.
Why pH and not acidity
Total acidity and pH measure different things and are not interchangeable. Total acidity is how much acid is present in total, found by titration; pH is how acidic the solution behaves, which depends on how much of that acid has dissociated and on what else in the liquid is buffering it. Two ciders with identical total acidity can differ in pH by a wide margin, most often because of differences in potassium content, which comes from the fruit and the soil.
The palate responds mostly to total acidity. Microbiology and sulphite chemistry respond to pH. That is why a maker who wants to know how a cider will taste titrates, and a maker who wants to know whether it is safe measures pH — and why both instruments earn their place.
The pH also sets the antimicrobial value of sulphur dioxide. Only the molecular form is effective, and the proportion in that form falls sharply as pH rises, so the same addition that protects a low-pH juice may do very little in a high-pH one. Any dosing decision made without a pH reading is being made blind, which is why CiderHQ points readers at the supplier’s own dosing guidance in conjunction with a measured pH rather than at a remembered figure.
Calibrating properly
Calibration is done against standard buffer solutions of known pH, at the temperature the samples will be at. Two-point calibration, typically with a pH 7.00 buffer and a pH 4.00 buffer, brackets the range cider sits in and corrects both the offset and the slope of the electrode response. A single-point calibration corrects the offset only and is not adequate for a working instrument.
Buffers have a shelf life and are contaminated by the probe itself. They are poured into a small clean vessel for use and discarded afterwards, never returned to the bottle. A bottle of buffer that has been dipped into repeatedly for a season is not a standard any more.
Frequency depends on use and on how much the decision depends on the number. Calibrating at the start of every session in which pH will be used for a decision is the defensible practice; calibrating once a year is not. A meter whose slope has degraded beyond the range the instrument will accept is telling you the probe has reached the end of its life.
Looking after the probe
- The glass bulb must stay wet. A probe stored dry loses response and may not recover; it is kept in the manufacturer’s storage solution, which is normally a potassium chloride solution.
- It must never be stored in distilled or deionised water. That leaches ions out of the bulb and out of the reference junction and ruins the electrode — a common and expensive mistake.
- Rinse between samples with distilled water and blot rather than wipe; rubbing the bulb generates a static charge that disturbs the reading.
- Refillable probes need their reference electrolyte topped up and the fill hole opened during measurement.
- Probes are consumables with a service life of a small number of years. A probe that responds slowly, drifts, or will not calibrate is replaced rather than argued with.
- Suspended solids and heavy colour do not interfere with pH the way they do with a titration endpoint, which is one of the reasons a meter is preferred over indicator paper or a colour endpoint in cider.
Temperature and reading discipline
pH varies with temperature, and a meter with automatic temperature compensation corrects the electrode’s response but not the genuine temperature dependence of the sample itself. Readings are therefore taken at a consistent temperature, and a pH quoted without a temperature is incomplete for any careful purpose.
A reading is taken with the probe stirred gently in the sample and allowed to stabilise, which may take a minute or more on a cold sample or an ageing probe. Recording a number the moment it appears on the screen is the commonest source of avoidable error.
Also answered on this page
Questions this page covers, so you can tell at a glance whether it is the one you want.
- What pH should cider be?
- How often should I calibrate a pH meter?
- Can I store a pH probe in water?
Related
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.
- 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.
- How do i measure the acidity of cider
- 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.
- How is free and total sulphur dioxide measured in cider
- What is mousiness in cider — Mousiness is a fault caused by tetrahydropyridines produced by *Brettanomyces* and some lactic acid bacteria. It tastes of stale grain or a mouse cage and appears in the aftertaste rather than in the aroma.
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.
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.
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.
Where to go next
- Cider making equipment — The rest of the equipment material, grouped by what each piece is for.
- How cider is made — The methods this equipment exists to carry out.
- Troubleshooting — The faults that are traced back to equipment and to cleaning.