Juice treatment
Sanitation
The cleaning and sanitising discipline that underlies every other process, and why removing soil must come before any attempt to kill organisms.
Also called Cleaning and sanitising, Hygiene, Plant cleaning.
- Stage
- Juice treatment
- Traditional in
- No single tradition — used wherever it suits
- What it most changes
- Not recorded as moving a sensory dimension
- Safety
- Carries a safety consideration — see below
Caustic and strong acid cleaners cause severe chemical burns and eye injury; they require appropriate gloves, eye protection and a known route to an eyewash, and concentrates should be added to water rather than water to concentrate. Never mix a chlorine-based sanitiser with an acid cleaner or acid sanitiser: the combination liberates chlorine gas, which is acutely dangerous in an enclosed cellar, and the same risk arises from rinsing one incompletely before applying the other. Hot caustic circulated through a sealed tank can create a vacuum as it cools and collapse the vessel, so venting must be confirmed. Entry into a tank for manual cleaning is confined-space work, with both an oxygen-deficiency and a chemical-residue hazard, and should not be undertaken alone.
What it is
Sanitation is two operations that are habitually confused. Cleaning removes soil — juice residue, pomace, protein, tartrate and other deposits, and the biofilm that grows on them. Sanitising reduces the microbial population on an already clean surface. The order is not negotiable and the second does not work without the first. In a cider plant the work covers everything the fruit and juice touch: mill, press cloths, pumps, hoses, valves, tanks, racking gear, bottling equipment and the floor and drains around all of it, and it is the base discipline on which every other process depends.
Why it is used
- Most cider faults with a microbial origin — acetification, ropiness, film yeast growth, lactic off-flavours — trace back to a resident population in equipment rather than to the fruit.
- A hose or valve carrying an established biofilm reinoculates every batch that passes through it, so the fault recurs no matter how carefully individual batches are handled.
- Zygosaccharomyces bailii and similar spoilage yeasts tolerate sulphite, sorbate and low pH, so they cannot be managed chemically in the product and must be excluded physically from the plant.
- Clean equipment allows lower sulphite use, because the microbial load the sulphite has to control is smaller to begin with.
How it works
- Organic soil consumes sanitiser directly. Chlorine- and peroxide-based sanitisers are oxidisers, and juice residue, protein and yeast debris are oxidisable, so a sanitiser applied to a dirty surface is spent on the soil before it reaches the organisms.
- Soil also shelters organisms physically: cells beneath a film of dried juice or inside a crevice are never contacted by the sanitiser at all, whatever its concentration.
- Alkaline cleaners, typically caustic-based, saponify fats and dissolve protein; acid cleaners remove mineral and tartrate scale. Alternating them prevents the build-up that either alone leaves behind.
- Biofilm is not loose soil. Organisms in a mature biofilm sit in a self-produced polysaccharide matrix that resists both chemical penetration and rinsing, and removing it requires mechanical action — flow velocity, brushing, or a pigging device — not just a longer soak.
- Sanitisers vary in what they leave: peracetic acid and ozone break down to innocuous residues, quaternary ammonium compounds persist and can taint, and iodophors stain and can carry over flavour, so rinse requirements differ by chemistry.
The chemistry and the organisms
What is actually being changed, and by what. Each entry says what that compound or organism does in cider generally; this page is one place it does it.
Compounds involved
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.
Acetic acid
The vinegar acid, made by bacteria oxidising ethanol whenever air reaches a cider, and the one fault in cider that no later processing can undo.
Organisms involved
Acetobacter aceti
An acetic acid bacterium that oxidises ethanol to acetic acid wherever cider meets air, and the organism behind most volatile acidity in cider.
Acetobacter pasteurianus
The film-forming acetic acid bacterium of traditional vinegar production, and a common cause of surface growth and volatile acidity in cider.
Gluconobacter oxydans
A sugar-preferring acetic acid bacterium abundant on damaged fruit and in fresh juice, which oxidises glucose to gluconic acid before fermentation begins.
Zygosaccharomyces bailii
A preservative-resistant spoilage yeast that refements sweetened cider and juice, and one of very few organisms able to grow through sorbate and benzoate at cider strength.
Lactobacillus collinoides
A lactic acid bacterium first described from cider, and the organism most closely associated with acrolein bitterness through its conversion of glycerol.
Film yeasts
A functional grouping rather than a taxon: the oxidative yeasts that form a skin on cider exposed to air and consume its alcohol and acid.
What it is done with
Sanitation: clean, sanitised, and why it decides the batch
Cider is an unsterile liquid at a pH and alcohol level that many spoilage organisms tolerate, so what survives on the equipment goes into the batch — which makes hygiene the largest single determinant of whether a small-scale ferment turns out drinkable.
Caustic and acid cleaning
Alkaline cleaners dissolve organic soil — fats, proteins and the residues of fermentation; acid cleaners dissolve mineral soil such as tartrate and calcium scale, and restore the passive layer on stainless steel. Both are hazardous chemicals used under the supplier’s own instructions.
Peracetic acid and other sanitisers
Peracetic acid is the commonest commercial sanitiser in beverage work because it is a powerful oxidant that breaks down to acetic acid, water and oxygen; the alternatives — acid-anionic, iodophor, hot water, steam and ozone — each have their own place and their own hazards.
Cleaning in place
Clean-in-place circulates cleaning and sanitising solutions through closed vessels and pipework at a controlled temperature, concentration and flow, so that equipment too large or too enclosed to be reached by hand is cleaned reliably and repeatably.
What can go wrong
Faults that begin at this step, or that this step makes more likely. Each one is set out with its causes and whether it can be put right.
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.
Acetification
The active conversion of a cider’s ethanol into acetic acid by acetic acid bacteria at an air interface — the process, running in the vessel, that produces volatile acidity.
Ropiness
Cider that pours thick and pulls into an oily thread, caused by lactic acid bacteria secreting long-chain glucan polymers into the drink.
Microbial haze
Cloudiness caused by a growing population of spoilage organisms, and therefore a symptom of something worse rather than a clarity problem in itself.
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.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
Brettanomyces character
Farmyard, horse-blanket, smoky and sticking-plaster aromas from Brettanomyces yeast converting hydroxycinnamic acids into volatile phenols.
Mould taint
Musty, earthy, cellar-damp or rotten-fruit character carried in from mouldy fruit or from mouldy equipment, and a marker that the patulin question needs asking.
Mousiness
A retronasal taint of mouse cage, stale popcorn or crackers that appears only after swallowing — and that a substantial fraction of people cannot detect at all.
Vinegar fly contamination
Small flies carrying acetic acid bacteria and spoilage yeasts directly into juice and cider, and depositing them wherever they land.
Cork taint
A damp-cardboard, wet-newspaper mustiness from trichloroanisole, usually carried by a natural cork but capable of reaching cider by other routes.
Plastic and packaging taint
Plastic, rubber, adhesive or chemical notes picked up from unsuitable containers, liners, hoses, gaskets or cleaning residues.
Styles it produces
Categories in which this step is characteristic or required. Some name it in their definition; for others it is simply how they have always been made.
More on sanitation
The single most useful thing to understand about sanitation is the sequence, because getting it wrong is the commonest error in small cider plants. Sanitiser applied to a dirty surface does not work. Chlorine, peracetic acid and peroxide are oxidising agents and juice residue is oxidisable, so the sanitiser is consumed by the soil rather than by the organisms; meanwhile cells sitting under a film of dried juice are never contacted at all. Soil load first, by an alkaline clean with mechanical action and a thorough rinse, and sanitiser only afterwards on a surface that is already visibly and tactilely clean. A surface that feels slightly slippery or tacky is not clean, whatever it looks like.
Biofilm is the reason a plant develops a recurring fault it cannot shake off. Given a nutrient supply and a surface, bacteria and yeasts build a polysaccharide matrix that shelters them from both chemistry and flow. Hoses are the worst offenders — flexible, long, hard to see into, rarely dried, and frequently left with juice in them overnight. Valves, particularly butterfly valves with a seat that traps liquid, and the dead legs of badly designed pipework, come next. Sample taps are a classic reservoir. None of these is fixed by a stronger sanitiser; they need dismantling, physical cleaning and, where possible, redesign so that lines drain and dry. A hose hung to drain is worth more than a hose soaked in sanitiser and coiled wet on the floor.
Wood is the honest complication in this subject. A wooden vat cannot be sanitised to the standard a stainless tank can, because the surface is porous and organisms live in the timber, below the depth any chemical treatment reaches. Traditional West Country, Normandy and Asturian making has always worked with this rather than against it: the resident microflora of an old vat is part of what makes the cider, contributing the lactic and Brettanomyces-derived character those styles carry, and a vat that produces good cider is left to keep doing so. That is a coherent practice, not negligence. But it is also not transferable — a stainless plant making a clean modern cider has no such tolerance, since the same organisms that flavour a farmhouse cider are simply spoilage in a bright filtered product, and the wooden vessels in a mixed operation need to be handled as a separate microbiological world with their own equipment where practicable.
What a practitioner actually decides is where effort goes, because time is finite. The highest returns are on hoses, pumps and valves, on anything that touches finished cider after any stabilisation step, and on the filler, since contamination at packaging has nowhere left to be corrected. Presses and mills matter less in absolute terms because what follows them is a fermentation that will out-compete most of what they contribute, though a mill left uncleaned overnight in warm weather becomes a vinegar factory quickly. The failure to watch for is the plant that is scrupulous about sanitiser and casual about cleaning, which produces a false confidence: a great deal of chemistry, a great deal of documentation, and a biofilm quietly persisting in the racking hose.
Related processes
Steps that sit alongside this one, replace it, or depend on it having been done.
Fermentation
Fermentation vessels
The container a cider ferments in — wood, stainless, plastic, glass or concrete — and how its permeability, thermal mass and resident microflora shape the result.
Maturation
Barrel ageing
Holding cider in wood — which may mean an old neutral vat used simply as a vessel, or fresh or spirit-seasoned oak used as a source of flavour, and the two are not the same operation.
Juice treatment
Sulphiting
Adding sulphur dioxide to juice to suppress spoilage organisms and oxidative browning, at a level that only means anything once the juice pH is known.
Juice treatment
Juice storage
Holding unfermented juice sound between pressing and fermentation, by chilling, sulphiting, gas blanketing, freezing or aseptic filling.
Packaging
Bottling
Transferring finished cider into glass, where the dominant variable is how much oxygen the liquid picks up in the few seconds it takes to fill and close each bottle.
Juice treatment
Patulin control
Managing the mycotoxin produced by rot fungi in damaged apples, which is controlled by fruit selection rather than by any treatment applied to juice.
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 cider makers keep patulin out — By sorting rotten fruit out before milling, because patulin comes from moulds growing on damaged apples. Fermentation reduces what gets through, so fermented cider carries no limit where juice does.
- What should i ferment cider in — Anything inert, cleanable and closable: glass demijohns, food-grade plastic, stainless steel, or a wooden cask if you can keep it sound. Vessel shape and material change how much oxygen the cider sees and how fast it clears.
- Why is sulphite added to cider — Sulphur dioxide suppresses spoilage bacteria and wild yeast before fermentation and protects the finished cider from oxidation. How much of it is active depends strongly on pH, which is why low-acid juice is harder to protect.
- 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.
- Why does my cider taste like vinegar — Acetic acid bacteria have reached the cider and, given air, are converting its alcohol into acetic acid. The cause is almost always oxygen — an unfilled vessel, a leaking bung, or a slow transfer.
- Why does everyone say cleaning matters more than anything else — Cleaning removes soil — pomace, lees, tartrate, protein and the biofilm growing in it. Sanitising reduces the number of viable organisms on a surface that is already clean. They are two separate operations and the second does not work without the first.
Where to go next
- How cider is made — The whole sequence, stage by stage, with the choices open at each one.
- Cider science — The chemistry and microbiology the methods on this page rest on.
- Troubleshooting — What goes wrong, how to recognise it, and whether it can be reversed.
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.
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.
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 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.