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Research note 050 — 2026-09-04

Tonic Water and Quinine — A Drink That Puts a Ceiling on Bitterness

Tonic water's bitterness is made with a single compound: quinine. What sets it apart from many bitter foods and drinks is that this content is capped by upper limits whose shape differs by country. Measured concentrations of commercial products stay below those upper limits, and the upper limits themselves take different forms in the United States, Australia, New Zealand, the European Union, and Japan. One country writes a single number into law; another stacks the same number across two tables; another imposes only a labelling requirement rather than a number; and yet another stops at listing the substance in a register. The compound quinine itself was extracted in the 19th century from a raw material, cinchona bark, and even while the bark itself was still the whole story, more than one way of drinking it survived. This note lines up, in order, the upper limits on content, the measured values, the history of isolation, and the other drinks in which cinchona bark still remains — only within the range that the sources state.

What this page establishes

• Tonic water's bitterness is treated as the content of a single compound, quinine, and one study confirms that the measured values of two commercial brands fall below the U.S. legal upper limit.
• The form the upper limit on content takes differs by country: sources record a country that writes the number itself into law, a country that stacks the same number across two tables, a country that imposes only a labelling requirement, and a country that stops at listing the substance in a register.
• One encyclopedia records that quinine was extracted from cinchona bark in the 19th century, and that before that, cinchona bark itself was handled in more than one form, including as a decoction and as a cinchona-bark wine.
• A source directly addressing the origin of the practice of combining tonic water with gin has not yet been found.

Tonic water's bitterness is made with quinine

Tonic water is a carbonated beverage to which quinine (as the hydrochloride or sulfate salt) is added for the purpose of imparting bitterness. Narrowed to this single point, the bitterness of the drink called tonic water can be treated as the content of a single compound.

The measured values stay below the upper limit

In brands actually sold, the quinine content has been measured. A report that measured 2 brands in the U.S. market by fluorescence spectroscopy found undiluted quinine concentrations of 64.60 ± 3.66 ppm for Canada Dry and 64.50 ± 2.68 ppm for Schweppes. The same report also cites approximately 25-60 ppm as the typical concentration range for commercial tonic water.

These measured values can be set alongside the U.S. legal upper limit. U.S. regulation sets the upper limit for quinine used as a flavouring in carbonated beverages at 83 ppm as quinine, and also requires labelling. The measured values of 64.5-64.6 ppm stay roughly 20-25% below this 83 ppm upper limit.

The shape of the upper limit differs by country

How the upper limit on content is set differs in mechanism from country to country. The Australia and New Zealand code sets upper limits of 100 mg/kg for tonic drinks, bitter drinks and quinine drinks, 300 mg/kg for wine-based beverages and low-alcohol wine, and 300 mg/kg for mixed alcoholic beverages not elsewhere classified.

The same numbers, 100 mg/kg and 300 mg/kg, also appear, stacked and with item numbers attached, in the table that permits use as a food additive.

European Union regulation takes the form not of a numeric upper limit but of a labelling requirement. Quinine used as a flavouring in the production or preparation of a food must be named explicitly in the list of ingredients. No provision setting a numeric upper limit as such is found within the framework of this regulation.

Japan's treatment stops at listing the substance in a register. The List of Existing Food Additives lists 「キナ抽出物」 (cinchona extract) with an item name and definition, but this register does not state a standard for which foods it may be used in or for the amount of use itself.

A country with a numeric upper limit, a country with the number listed twice, a country that imposes only a labelling requirement, a country that stops at listing the substance in a register — around this single compound, quinine, the ways of treating content diverge this far.

From bark, a single point is drawn out: quinine

Before the single compound quinine took centre stage, there is the history of a raw material: cinchona bark. One encyclopedia records the history of cinchona bark in Europe as beginning at the start of the 17th century, and relates the 1638 anecdote of General López sending the powder to the Countess of Chinchón, alongside the nickname 『伯爵夫人の粉』 (in translation: "the Countess's powder"). The same account also touches on its spread through the Jesuits.

It was not until the 19th century that the single compound quinine was extracted from this bark. It is recorded that in 1820 the French chemists Pelletier and Caventou found quinine (chinina) and cinchonine (cinchonina) in cinchona bark.

Before being drawn out as a compound, cinchona bark was handled in more than one form, still as bark. Among the forms listed alongside a decoction, an elixir, and a tincture is vino chinato, a name meaning cinchona-bark wine. Even before being drawn out as a single compound, cinchona bark had already taken the form of a drink.

Cinchona bark also remains in other bitter drinks

The raw material cinchona bark also remains in bitter drinks other than tonic water. A source on aromatic bitters for cocktails names cinchona bark as one of its core bittering ingredients.

Individual brands, too, name cinchona bark as an ingredient. Aperol's official FAQ names cinchona explicitly as one of its ingredients, alongside gentian. Outside tonic water as well, the raw material cinchona bark itself remains, even as it changes name.

What is not known

• A source directly addressing the practice of combining tonic water with gin has not been found within what we could read here. All that can be written is the lineup: cinchona bark also remains in other bitter drinks, such as aromatic bitters and Aperol.
• As to why the same numbers, 100 mg/kg and 300 mg/kg, appear both in the table for natural substances and in the table for food additives in the Australia and New Zealand code, the text of the code itself does not touch on this overlap.
• The description of the forms including vino chinato originates from a 1930s edition of the encyclopedia, and may differ from present-day classification.
• The absence of a numeric upper limit in European Union regulation is an absence within the range of the provisions we read; the check has not been widened to other frameworks.

Frequently asked

How much quinine is in tonic water?

A report that measured 2 brands of tonic water in the U.S. market by fluorescence spectroscopy records undiluted quinine concentrations of 64.60±3.66 ppm for Canada Dry and 64.50±2.68 ppm for Schweppes. The same report also cites approximately 25 to 60 ppm as the typical concentration range for commercial tonic water. This measurement was carried out as an educational protocol with 5 replicate student groups, is a result for only 2 brands, and is not a survey of the market as a whole. The upper limit set by U.S. regulation is 83 ppm, and the measured values stay below it.

Is there an upper limit on quinine content?

How the upper limit is set differs by country. U.S. regulation sets the upper limit for quinine used in carbonated beverages at 83 ppm as quinine, and also imposes a labelling requirement. The Australia and New Zealand code sets upper limits of 100 mg/kg for specific beverage categories such as tonic drinks, and 300 mg/kg for categories such as wine-based beverages, each in two tables of a different character. No numeric upper limit is found in European Union regulation; only a labelling requirement in the list of ingredients is set. In Japan, cinchona extract is listed as an item in the register of existing food additives, but this register does not state a standard for the amount of use itself.

Related entries:tonic water ／quinine ／Cinchona succirubra (bark extract) ／vino chinato ／aromatic cocktail bitters ／Aperol
Related research notes: The Bitterness of Medicine, and Being Drinkable ／How Thin a Bitterness Can People Notice — A Map of Thresholds ／What Do the Twenty-Five Bitter Receptors Divide Among Themselves? ／How Bitterness Gets Institutionalized — Bitterness Within a System
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