The topic of sulfite food and beverage additives covers the application of sulfites in

food chemistry Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. The biological substances include such items as meat, poultry, lettuce, beer, milk as examples. It is similar to biochemist ...

. "

Sulfite 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 wide ...

" is jargon that encompasses a variety of materials that are commonly used as preservatives or

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salt ...

in the production of diverse foods and beverages. Although sulfite salts are relatively nontoxic, their use has led to controversy, resulting in extensive regulations. Sulfites are a source of

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 ...

(SO₂), a bactericide.

Chemical principles

Inventory

sodium bisulfite Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions ...

, NaHSO₃: ill-defined, widely used source of

bisulfite The bisulfite ion (IUPAC-recommended nomenclature: hydrogensulfite) is the ion . Salts containing the ion are also known as "sulfite lyes". Sodium bisulfite is used interchangeably with sodium metabisulfite (Na2S2O5). Sodium metabisulfite disso ...

, which predominates below pH 7 *

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 ...

, Na₂S₂O₅: well-defined, widely used source of

, which predominates below pH 7 *

potassium bisulfite Potassium bisulfite (or potassium hydrogen sulfite) is a chemical mixture with the approximate chemical formula KHSO3. Potassium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions composed of ...

, KHSO₃: ill-defined, widely used source of

, which predominates below pH 7 *

potassium metabisulfite Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white crystalline powder with a pungent odour. It is mainly used as an antioxidant or chemical sterilant. As a disulfite, it is chemically very similar to sodium metabis ...

, K₂S₂O₅,: well-defined, widely used source of

, which predominates below pH 7 *

sodium sulfite Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na2 SO3. A white, water-soluble solid, it is used commercially as an antioxidant and preservative. A heptahydrate is also known but it is less useful because of ...

, Na₂SO₃: well-defined, widely used source of

sulfite 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 wide ...

, which predominates above pH 7 *

potassium sulfite Potassium sulfite is the inorganic compound with the formula K2SO3. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water. Use Potassium sulfite is widely used for preserving food and bever ...

, K₂SO₃: well-defined, widely used source of

, which predominates above pH 7

Descriptive chemistry

is SO₃^2-, available as its sodium and potassium salts, Na₂SO₃ and K₂SO₃, respectively. When dissolved in water, these salts react with oxygen to give the corresponding sulfate salts, which are innocuous. Sodium sulfite used industrial as a corrosion inhibitor/oxygen scavenger. Monoprotonation of sulfite gives HSO₃⁻, which is called bisulfite. The sodium and potassium salts of bisulfite are not available, but solid and solutions of the approximate formula NaHSO₃ and KHSO₃ are widely marketed as

and

. Closely related are the metabisulfite salts with formula Na₂S₂O₅ and K₂S₂O₅, respectively

and

. These salts dissolve to give solutions containing the bisulfite ion.

E numbers

E numbers E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly f ...

for sulfites as

food additives Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salt ...

are:

Use in wine and beer industry

Sulfites occur naturally in

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 ...

s to some extent. Sulfites are commonly introduced to arrest

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

at a desired time, and may also be added to wine as

preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by ...

s to prevent spoilage and

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

at several stages of the

winemaking Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The science of wine and ...

. Sulfur dioxide (SO₂) protects wine from not only oxidation, but also from bacteria. Without sulfites, grape juice would quickly turn to

vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to et ...

. Organic wines are not necessarily sulfite-free, but generally have lower amounts and regulations stipulate lower maximum sulfite contents for these wines. In general, white wines contain more sulfites than red wines and sweeter wines contain more sulfites than drier ones. The compound

is used in almost all commercial wines to prevent oxidation and preserve flavor, sodium bisulfite is sold by some home winemaking suppliers for the same purpose.The Many Uses Of Sodium Bisulfite
/ref> In fruit canning, sodium bisulfite is used to prevent browning (caused by oxidation) and to kill microbes. The sulfur dioxide released by these salts kills yeasts, fungi, and bacteria in the grape juice before fermentation. Once the levels of sulfur dioxide have subsided (about 24 hours), fresh yeast is added for fermentation. It is later added to bottled wine to prevent the formation of vinegar if bacteria are present, and to protect the color, aroma and flavor of the wine from oxidation, which causes browning and other chemical changes. Sodium metabisulfite and

are the primary ingredients in

Campden tablets Campden tablets (potassium or sodium metabisulfite) are a sulphur-based product that is used primarily to sterilize wine, cider and in beer making to kill bacteria and to inhibit the growth of most wild yeast: this product is also used to elimi ...

, used for

and

beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...

making. Most

s no longer contain sulfites, although some alcoholic ciders contain them.

Other foods

Shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

are sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label.

Vegetables and fruit

Sulfites are often used as

s in

dried fruit Dried fruit is fruit from which the majority of the original water content has been removed either naturally, through sun drying, or through the use of specialized dryers or dehydrators. Dried fruit has a long tradition of use dating back to th ...

s, preserved

radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an Eating, edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman Empire, Roman times. Radishes are grown and consumed throughout the world, be ...

, and dried

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

products. Sodium bisulfite is also added to leafy green vegetables in salad bars and elsewhere, to preserve freshness, under names like LeafGreen. It can be used to preserve color of some fruits, such as

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...

Regulation and safety

;Australia and New Zealand It is approved for use in Australia and New Zealand In Australia and New Zealand, sulfites must be declared in the statement of ingredients when present in packaged foods in concentrations of 10 mg/kg (ppm) or more as an ingredient; or as an ingredient of a compound ingredient; or as a food additive or component of a food additive; or as a processing aid or component of a processing aid. ;Canada Sulfites that can be added to foods in Canada are potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium dithionite, sodium metabisulfite, sodium sulfite, sulfur dioxide and sulfurous acid. These can also be declared using the common names sulfites, sulfates, sulfiting agents. ;EU In the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

, "EU law requires food labels to indicate “contains sulfites” (when exceeding 10 milligrams per kilogram or per litre) without specifying the amount". In the

an equivalent regulation came into force in November 2005. In 2012, a new regulation for organic wines came into force. ;UK In the United Kingdom, similar laws to the EU apply. Bottles of wine that contain over 10 mg/L (ppm) of sulfites are required to bear "contains sulphites" on the label. This does not differ whether sulfites are naturally occurring or added in the winemaking process. ;US In 1986, the U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

banned the addition of sulfites to all fresh fruit and vegetables that are eaten raw. In 1986, the U.S. Food and Drug Administration banned the use of sulfites as preservatives on foods intended to be eaten fresh (such as salad ingredients). This has contributed to the increased use of

erythorbic acid Erythorbic acid (isoascorbic acid, D-araboascorbic acid) is a stereoisomer of ascorbic acid (vitamin C). It is synthesized by a reaction between methyl 2-keto-D-gluconate and sodium methoxide. It can also be synthesized from sucrose or by strains ...

and its

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...

as preservatives. Generally, U.S. labeling regulations do not require products to indicate the presence of sulfites in foods unless it is added specifically as a preservative; still, many companies voluntarily label sulfite-containing foods. Sulfites used in food processing (but not as a preservative) are required to be listed if they are not incidental additives (21 CFR 101.100(a)(3)), and if there are more than 10 ppm in the finished product (21 CFR 101.100(a)(4)) On July 8, 1986, sodium bisulfite (and other sulfites : "The chemicals affected by the order are sulfur dioxide, sodium sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite and potassium metabisulfite.") was banned from use by the U.S.

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

on fresh fruits and vegetables following the deaths of 13 people and many illnesses, mainly among asthmatics. In the United States, wines bottled after mid-1987 must have a label stating that they contain sulfites if they contain more than 10 parts per million (ppm).

Safety

Toxicity

Sodium bisulfite has low toxicity, 130 mg/kg (mice, intravenous). According to another source, the

acceptable daily intake Acceptable daily intake or ADI is a measure of the amount of a specific substance (originally applied for a food additive, later also for a residue of a veterinary drug or pesticide) in food or drinking water that can be ingested (orally) daily ove ...

is up to 0.7 milligrams per kilogram of body weight. Sodium metabisulfite oxidizes in the liver to harmless

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...

which is excreted in the urine.

Other health effects

It may cause adverse reactions in those who are sensitive 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 ...

, including

respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...

reactions in

asthmatics Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

anaphylaxis Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follow ...

, and other allergic reactions in sensitive individuals. Adverse reactions to sulfites appear to be very rare in the general population. An adverse reaction to sulfite is not a true allergy. Chronic skin conditions in the hands,

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...

, and face have been reported in individuals that regularly use cosmetics or medications containing sulfites. Occupational exposure to sulfites has been reported to cause persistent skin symptoms. Breathing difficulty can commence within minutes after eating a food containing sulfites.

Asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

tics may experience asthma attacks from sulfite fumes as well. Other potential symptoms include

sneezing A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and ...

, swelling of the

throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebrae. It contains the pharynx and larynx. An important section of it is the epiglottis, separating the esophagus from the trachea (windpipe ...

hives Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and does not leave any long-lasti ...

, and

migraine Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...

. A 2017 study has shown negative impacts from sulfites on bacteria found in the human

microbiome A microbiome () is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupying a reasonably well ...

.{{cite journal , vauthors = Irwin SV, Fisher P, Graham E, Malek A, Robidoux A , title = Sulfites inhibit the growth of four species of beneficial gut bacteria at concentrations regarded as safe for food , journal = PLOS ONE , volume = 12 , issue = 10 , pages = e0186629 , date = 2017-10-18 , pmid = 29045472 , pmc = 5646858 , doi = 10.1371/journal.pone.0186629 , bibcode = 2017PLoSO..1286629I , doi-access = free

Chemical principles

Inventory

Descriptive chemistry

E numbers

Use in wine and beer industry

Other foods

Vegetables and fruit

Regulation and safety

Safety

Toxicity

Other health effects

References