Compound
Thiamine
A vitamin yeast cannot ferment without, frequently limiting in cider juice, and destroyed by the sulphite added to protect that juice.
Also called Vitamin B1.
- Class
- Nitrogen compounds
- Formula
- Not a single molecule — see below
- How often it matters
- Occasional
What it does in cider
- Serves as the cofactor for pyruvate decarboxylase, the enzyme that converts pyruvate to acetaldehyde and therefore makes alcoholic fermentation possible at all.
- Is present in apple juice at variable and often marginal concentrations, so cider ferments are more prone to deficiency than most.
- Is degraded by sulphur dioxide, so a heavily sulphited juice can be short of it whatever the fruit supplied.
- Leaves a ferment producing excess pyruvate when it runs short, and pyruvate is itself a sulphite binder that consumes further additions.
What forms it
Processes that put this compound into the drink, or increase how much of it is there.
Nutrient addition
Supplementing a characteristically nitrogen-poor juice so that yeast can complete fermentation without producing sulphide or stalling.
Yeast nutrition
What a fermenting yeast population actually needs from apple juice — assimilable nitrogen, vitamins and membrane lipids — and what goes wrong when the juice cannot supply it.
What removes or limits it
Processes that reduce it, hold it below a threshold, or stop it forming in the first place.
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.
Wild fermentation
Letting the microflora already present on the fruit and in the press house carry the ferment, in a succession rather than as a single organism.
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
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.
Stuck fermentation
A fermentation that has stopped before the sugar is gone and will not restart, leaving a sweet, low-alcohol cider that is vulnerable to everything.
Sluggish fermentation
A fermentation that is still moving but far more slowly than it should, extending the period during which the cider is weak, sweet and exposed.
Nitrogen deficiency character
The set of characters a nitrogen-starved fermentation produces together — sulphide, a stalled or dragging ferment, harsh higher alcohols and a thin, hard cider.
Excess sulphur dioxide
A struck-match or burnt-match aroma and a prickle at the back of the nose from too much free sulphur dioxide, with a real health consideration for sulphite-sensitive people.
Hydrogen sulphide
A rotten-egg or drain smell from hydrogen sulphide produced by stressed yeast, usually the first visible consequence of a nitrogen-short juice.
Organisms that produce it
Which organism is responsible usually decides whether the compound is a feature or a symptom.
About Thiamine
Thiamine pyrophosphate is the cofactor of pyruvate decarboxylase, and pyruvate decarboxylase is the enzyme that makes fermentation fermentation: without it, pyruvate is not converted to acetaldehyde and there is no route to ethanol. A yeast short of thiamine does not fail dramatically, it works badly, and the resulting slow ferment is easily blamed on temperature or on nitrogen.
Two things make cider particularly vulnerable. Apple juice carries thiamine at concentrations that are often close to the requirement rather than comfortably above it, and sulphur dioxide destroys the vitamin. Sulphiting a juice heavily to control its microbiology therefore removes part of what the yeast needed, and the practice of adding thiamine along with nitrogen exists precisely because the two deficiencies so often travel together.
A shortage leaves a chemical trace. Yeast starved of thiamine accumulates and excretes pyruvate, and pyruvate binds sulphite — so a thiamine-deficient ferment produces a cider that then absorbs sulphite additions without becoming better protected. It is a small compound with a disproportionate ability to make several other problems worse at once.
Related compounds
Compounds it is formed from, converted into, confused with, or routinely met alongside.
Nitrogen compounds
Yeast-assimilable nitrogen
The nitrogen a yeast can actually use, which apple juice is chronically short of — the shortage behind both stuck fermentations and rotten-egg aromas, and the shortage keeving deliberately makes worse.
Nitrogen compounds
Ammonium nitrogen
The nitrogen form yeast takes up fastest and the one most nutrient additions supply, useful for rescuing a ferment and a poor substitute for a properly balanced juice.
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.
Aldehydes
Acetaldehyde
The compound sitting one step short of ethanol, which smells of bruised apple and sherry, binds most of the sulphite added to a cider, and is the chemical signature of oxidation.
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.
- Why did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- Which yeast ferments cider — Saccharomyces cerevisiae finishes almost every cider fermentation, whether it was pitched or arrived from the press house. In a spontaneous ferment it is not the first organism present, only the one that survives the alcohol it makes.
- What does a nitrogen-starved cider taste like
- What is yan and why does cider juice run short of it — Yeast assimilable nitrogen is the nitrogen yeast can actually use. Apple juice is usually short of it — in one Virginia survey of 108 samples, 94 per cent fell below the level wine practice treats as a minimum — which is why cider ferments stall more readily than wine ferments.
- Why is my cider fermenting so slowly
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.
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.
Hochschule Geisenheim University — beverage technology
Hochschule Geisenheim · university · retrieved 2026-08-24
German beverage-technology research covering apple wine and fruit juice processing, including the enzymology of clarification.