Campden tablets (

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

sodium metabisulfite Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. It is used a ...

) are a

sulphur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

-based product that is used primarily to sterilize

wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...

cider Cider ( ) is an alcoholic beverage made from the fermented juice of apples. Cider is widely available in the United Kingdom (particularly in the West Country) and the Republic of Ireland. The UK has the world's highest per capita consumption, ...

and in beer making to kill

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and to inhibit the growth of most wild yeast: this product is also used to eliminate both free

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

and the more stable form,

chloramine Chloramines refer to derivatives of ammonia and organic amines wherein one or more N-H bonds have been replaced by N-Cl bonds. Two classes of compounds are considered: inorganic chloramines and organic chloramines. Inorganic chloramines Inorgan ...

, from water solutions (e.g., drinking water from municipal sources). Campden tablets allow the amateur brewer to easily measure small quantities of sodium metabisulfite, so it can be used to protect against wild yeast and bacteria without affecting flavour. Untreated cider

must Must (from the Latin ''vinum mustum'', "young wine") is freshly crushed fruit juice (usually grape juice) that contains the skins, seeds, and stems of the fruit. The solid portion of the must is called pomace and typically makes up 7–23% of t ...

frequently suffers from

acetobacter ''Acetobacter'' is a genus of acetic acid bacteria. Acetic acid bacteria are characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. Of these, the genus ''Acetobacter'' is distinguished by the ability to oxidize ...

contamination causing vinegar spoilage. Yeasts are resistant to the tablets but the acetobacter are easily killed off, hence treatment is important in cider production. Typical use is one crushed Campden tablet per US gallon (3.8 L) of

wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...

. This dosage contributes 67 ppm

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...

to the wort but the level of active sulfur dioxide diminishes rapidly as it reacts with chlorine and chloramine, and with

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

(particularly in wine). Therefore, the concentration of free sulfur dioxide is greatly diminished by the time the beer or wine is consumed. However, when used only for the purpose of dechlorinating tap water before brewing, one tablet will effectively treat 20 US gallons (75 L) of water. Campden tablets are also used as an anti-oxidizing agent when transferring wine between containers. The sodium metabisulfite in the Campden tablets will trap oxygen that enters the wine, preventing it from doing any harm. It is a common misconception that Campden tablets can be used to halt the ferment process in wine before all the available sugars are converted by the yeast, hence controlling the amount of residual sweetness in the final product. This however is not true. In order to halt fermentation, enough Campden tablets would have to be added to render the wine undrinkable. Alternatively, when used in conjunction with

potassium sorbate Potassium sorbate is the potassium salt of sorbic acid, chemical formula CH3CH=CH−CH=CH−CO2K. It is a white salt that is very soluble in water (58.2% at 20 °C). It is primarily used as a food preservative (E number 202). Potassium sor ...

, the yeast population will be greatly reduced and prevented from reproducing. Without the addition of

the yeast population will only be stunned and eventually repopulate if provided with enough fermentable sugars. Campden tablets typically contain 0.44 g each of sodium metabisulfite (plus filler) and 8 of these are equivalent to one half level teaspoon (2.5 mL) of sodium metabisulfite. Other Campden tablet formulations use potassium metabisulfite. Each is also referred to interchangeably as—sulfites, and the 'bi' can be found as 'di'. In terms of usage, sodium

thiosulfate Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...

is a closely related compound. The name Campden tablet comes from the town of

Chipping Campden Chipping Campden is a market town in the Cotswold district of Gloucestershire, England. It is notable for its terraced High Street, dating from the 14th century to the 17th century. ("Chipping" is from Old English ''cēping'', 'market', 'market- ...

Gloucestershire Gloucestershire ( abbreviated Glos) is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn and the entire Forest of Dean. The county town is the city of Gl ...

, England, where the original solution was developed in the 1920s by the Fruit and Vegetable Preserving Research Station - now

Campden BRI Chipping Campden is a market town in the Cotswold (district), Cotswold district of Gloucestershire, England. It is notable for its terraced High Street, dating from the 14th century to the 17th century. ("Chipping" is from Old English ''cēping' ...

. The idea was then taken up by the Boots Co., who developed the tablet. Campden tablets are also useful in decontamination and neutralization after exposure to

tear gas Tear gas, also known as a lachrymator agent or lachrymator (), sometimes colloquially known as "mace" after the early commercial aerosol, is a chemical weapon that stimulates the nerves of the lacrimal gland in the eye to produce tears. In ad ...

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molar mass In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, p ...

(commonly called molecular weight or MW) of potassium metabisulfite is 222 g/mol, while the molecular weight of sodium metabisulfite is 190 g/mol.

Health Effects

Some people have allergies or intolerance to

sulfites Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous acid) is elusive, its salts are widel ...

. Allergies are less common than intolerance, but in rare cases may cause life-threatening anaphylactic reaction. Products containing residual amounts of sulfites, including potassium metabisulfite and sodium metabisulfite, should be labelled.

References

External links

Kitchen Dictionary: Campden Tablet
Chipping Campden Homebrewing Science and technology in Gloucestershire Sulfites Winemaking