Winemaking
What actually goes into wine
A neutral account of permitted additives and processing aids — what they are for, and why "chemicals in wine" is the wrong frame.
The short answer
Beyond grapes and yeast, winemaking permits a defined list of additives and processing aids: sulfur dioxide, yeast nutrients, fining agents, acids, enzymes and tannins among them. Most are processing aids that are removed before bottling. The list is regulated and public.
Overview
Two opposite framings dominate this subject and both are unhelpful. One treats any addition as adulteration; the other dismisses the question as ignorant. Neither tells a reader what is actually permitted or why.
The regulated distinction is between an additive, which remains in the finished wine and may require declaration, and a processing aid, which does a job and is then removed.
Step by step
1 Sulfur dioxide
Antioxidant and antimicrobial, and the only one that must be declared on the label above 10 mg/L. Also produced naturally by yeast.
2 Yeast nutrients
Nitrogen compounds and vitamins, added where the must is deficient. The main defence against stuck fermentation and against reductive sulfur faults.
3 Fining agents
Bentonite clay, egg white, casein, gelatin, isinglass, pea and potato protein. Bind unwanted material so it can be removed; they are then removed themselves.
4 Acids and carbonates
Tartaric acid to raise acidity, carbonates to lower it, within jurisdictional limits.
5 Enzymes
Pectinases to aid clarification and pressing; others to release bound aroma compounds.
6 Oenological tannins
Tannin preparations from oak or grape, used to stabilise colour or adjust structure.
7 Sugar or concentrated must
For enrichment before fermentation, where permitted. Consumed by the yeast.
What people get wrong
2 widely repeated claims this page corrects.
Not true
“Wine is fermented grape juice, so of course it is vegan.”
Some wines are fined with animal-derived agents — egg white, casein, gelatin, isinglass. The agents are removed before bottling, but many people still prefer to avoid wines made that way.
Depends
“Natural wine is legally defined and has nothing added to it.”
In most jurisdictions "natural wine" has no legal definition at all. Certification schemes exist and vary, and the terms natural, organic, biodynamic, unfined and unfiltered are not synonyms.
EU labelling rules changed substantially with the introduction of ingredient and nutrition declarations for wine, generally accessible via an e-label. What must appear, and where, differs by jurisdiction.
WineHQ neither treats additions as inherently suspect nor dismisses the question. It describes what each does and cites the regulation that permits it. It makes no health claim about any of them.
Sources
Sources consulted
More in winemaking
Winemaking
Fermentation
Yeast converting sugar into alcohol and carbon dioxide — the step that makes wine wine.
Winemaking
How red wine is made
Fermenting grape juice in contact with the skins, which is where colour and tannin come from.
Winemaking
How white wine is made
Pressing the juice off the skins before fermentation, then fermenting the clear juice.