What is Potassium Metabisulfite (E224)? Uses, Safety, Side Effects

What is Potassium Metabisulfite (E224)? Uses, Safety, Side Effects

What is potassium metabisulfite

Table of Contents

Potassium Metabisulfite (E224) is a chemical preservation agent used to treat grape products, and in the production of beer and wine. The substance helps preserve wine’s color, clarity, taste, and smell by maturing it.

Moreover, it has the ability to preserve fruits and vegetables by removing their destructive toxins. Therefore, when used in combination with Citric Acid, Potassium Metabisulfite or E224 serves as a preservative that offers reliable protection against the bacterial activity.

What is potassium metabisulfite in food?

Potassium metabisulfite is a food additive that improves the shelf life of food and prevents discoloration. It also inhibits the growth of bacteria in wine and beer.

Potassium metabisulfite is a white to light yellow crystalline powder or granule, or as a light greenish-yellow or brownish-yellow liquid. It has an odor similar to sulfur dioxide (SO2) and a bitter taste.

Potassium metabisulfite is used in foods such as canned vegetables, dried fruits and fruit juices, potato chips, pretzels and other snacks, carbonated beverages, pickles and relishes, baked goods, canned tuna fish and other fish products, canned shellfish and other seafood products, salad dressings, dehydrated potatoes and vegetables, powdered egg whites for use in eggnog mixes and other dairy products such as whipping cream and buttermilk powder.

What is potassium metabisulfite used for?

Potassium metabisulfite is a chemical compound that has many uses. It is used in winemaking and beer brewing to remove sulfide compounds that can impart an off flavor to wines, and it is also used to preserve foods.

Potassium metabisulfite is a common ingredient in food preservatives, and it can be found in jams, jellies, dried fruits, and juices. It is also used as an antioxidant in wine, beer, and other products.

Potassium metabisulfite is used in winemaking, beer brewing, and cider making as a preservative to prevent oxidation. In addition to preserving food, potassium metabisulfite can also be used as a bleaching agent for flour and other grains.

Potassium metabisulfite has a number of other uses as well. It is often used as a bleaching agent for textiles — especially cotton fabrics — because it removes color from natural dyes without being strong enough to damage the fabric itself. The compound has also been used to treat skin conditions such as eczema and psoriasis because it helps reduce inflammation caused by these conditions.

The compound was first discovered in 1846 by German chemist Friedlieb Ferdinand Runge (1803-1867) while he was studying the effect of light on silver chloride solutions with potassium bromide (KBr). Runge discovered that when he exposed some KBr solution to light under certain conditions he got a white precipitate (potassium bromate) that could dissolve easily

How is Potassium Metabisulfite made?

A potassium metabisulfite is generally produced by reacting sulfur dioxide with potassium carbonate between 50°C and 80°C and at a pH between 4 and 7.5.

Here are three steps in the manufacturing process:

Potassium sulfite is obtained by treating potassium hydroxide and/or potassium carbonate solutions with sulfur dioxide gases. The chemical equation for the reaction is: K2CO3 + SO2 + H2O = K2SO3 + H2CO3

Continue adding sulfur dioxide to the aqueous solution until saturation is reached. During this process, potassium sulfite is converted into potassium bisulfite. The reaction equation is: K2SO3 + SO2 + H2O = 2KHSO3.

After cooling down the reaction mixture, potassium metabisulfite (K2S2O5) can be obtained by filtration or centrifugation. The reaction equation is: 2KHSO3 = K2S2O5 + H2O


Other names Potassium disulphite, Potassium pentaoxo disulphate
CAS number 16731-55-8
Chemical formula K2S2O5
Molecular weight 222.33


Powder or granules that are white or colorless.


Potassium metabisulfite structure


The compound is soluble in water (250 g/L at 0°C and 44.9 g/100ml at 20°C); it is insoluble in ethanol. In the air, it releases sulfur dioxide (SO2) gas as a result of gradual oxidation to potassium sulfate (K2SO4).

The aqueous solution of 1% bisulfite is acidic, with a pH 3.4-4.5 (hydration relative standard deviation 4%).

This is the equation for the interaction with water: K2S2O5 + H2O -> 2 KHSO3

What’s the application of potassium metabisulfite?

Food grade potassium metabisulfite has a wide range of applications in industry and chemistry.

Potassium metabisulfite is an important chemical reagent used in the food and beverage industries, where it is used as a preservative to prevent bacterial growth. It is also used in the textile industry as an antiseptic and bleaching agent.

Potassium metabisulfite can be used to preserve fruit juices, wines, and other alcoholic beverages by inhibiting microbial growth during storage. In this application, potassium metabisulfite serves two purposes: firstly it acts as a bactericidal agent that kills unwanted microorganisms; secondly it acts as an antioxidant by reacting with free radicals formed during fermentation (which can cause off-flavors) or from exposure to oxygen. 

The antimicrobial action of potassium metabisulfite results from its ability to form a complex with iron ions present in water (Fe(II)), which are required for bacterial respiration1.

How does potassium metabisulfite work?

Potassium metabisulfite is an oxidizing agent that is used to stabilize wine and beer. It is added to wine and beer to prevent oxidation from occurring during the fermentation process.

When potassium metabisulfite comes into contact with an aqueous solution, it will produce sulfur dioxide (SO2) gas. This happens because the potassium ions in the solution are reduced to sulfate ions, which then react with oxygen molecules (O2) to form SO2 gas.

The amount of SO2 produced depends on the concentration of potassium metabisulfite added, as well as its pH level and temperature.


It has been used worldwide for the manufacture of wine using potassium metabisulfite. Wine labels often mention sulfur dioxide, but unlike many other ingredients, it is not commonly added directly to wine, but rather produced by adding sodium metabisulfite or potassium metabisulfite.

As a preservation, sterilization, and stability agent in grape picking, brewing, storing, and bottling processes, SO2 (sulfite, metabisulfite, bisulfite) is used.

The solid potassium metabisulfite releases sulfur dioxide when added to wine. The mechanism by which it reacts with water in wine is as follows.

  1. K2S2O5 + H2O 2K+ + 2(HSO3)-
  2. HSO3- + H+ H2O + SO2

There are two main forms of sulfur dioxide in wine: free state and combined state. In addition to its bactericidal and antioxidant properties, sulfur dioxide only has a free form.

HSO3- (bisulfite) and SO32- (sulfite) are the main acid radical ions in combined SO2. There is a sulfurous smell to free SO2, which is dissolved sulfurous acid (H2SO3)or SO2.

Purposes of SO2 in winemaking

Oxidation and spoilage are most likely to occur in the part of the wine that is in contact with the air. The key to ensuring wine storage is to increase the sulfur dioxide content on the wine surface.

1. Preservative

A wine’s quality can be improved by inhibiting the growth of harmful microorganisms (e.g. wild yeast, lactic acid bacteria, and acetic acid bacteria).

2. Antioxidant

In wine, SO2 can scavenge oxygen, hydrogen peroxide, and free radicals, thus slowing the aging process of the wine due to oxidation (e.g. browning, aroma loss, bitterness).

As compared to other ingredients in wine, SO2 is the most likely to react with oxygen and oxidize into sulfuric acid or sulfate, therefore inhibiting or delaying the oxidation of other components.

In addition, SO2 inhibits the activity of polyphenol oxidase and peroxidase as well as Vitamin C loss and Maillard reaction.

Moreover, SO2 can combine with carbonyl compounds, such as acetaldehyde, pyruvic acid, and 2-hydroxyglutaric acid, to improve wine’s flavor.

When to add potassium bisulfite?

Wine made from fresh grapes or fruits needs SO2 during almost every step, including fermentation, aging, storage, and bottling.

During the crush, it is added before using yeast to kill wild yeasts, molds, and bacteria present in the must. Fermentation will lose SO2 and discharge it along with CO2, so it needs to be added at the end.

In both storage and bottling, they prevent spoilage caused by microorganisms and scavenge oxygen.

Potassium sorbate is another preservative that may be added just before bottling. As this ingredient inhibits the natural yeast from further multiplying, it cannot be used before or during fermentation.

How much potassium bisulfite to eat?

Wine making, storage, and bottling require a certain amount of free sulfur dioxide.

Here is the chemical balance formula based on the PH value: H2O + SO2⇌H2SO3⇌H+ + HSO3 –

By comparing low pH wines with higher pH wines, we can learn that low pH wines require less SO2.


It is also possible to use potassium metabisulfite in beer brewing to eliminate free oxygen and inhibit the growth of wild yeasts and bacteria, but this is not commonly done. In wine, the concentration is around 5%-10%.


Lemon juice ingredient lists may also include it. Citric acid, malic acid, tartaric acid, tannins, sugar, minerals, and other components are found in the extracted lemon juice.

In the juice manufacturing facility and in the fruit itself, microorganisms are likely to be present that can cause contamination.

As an antimicrobial agent, potassium metabisulfite should be added to juice after pressing to prevent juice browning (acting as an antioxidant).

Is potassium metabisulfite safe?

The safety of potassium metabisulfite has been approved and there are almost no side effects (except for an allergy caused by sulfur dioxide).

FDA recognizes it as safe when used as a chemical preservative, but it cannot be used on fresh or raw fruits and vegetables, meat, or foods containing vitamin B1.

In Regulation (EU) No 231/2012, potassium metabisulfite (E224) is listed as an authorized food additive under “additives other than colors and sweeteners”.

EFSA re-evaluated its safety in 2016, concluding that the current group ADI of 0.7 mg/kg BW per day for E220-E228 was temporary and would be re-evaluated due to uncertainty and limitations in the database.

In addition to wine, beer, cider, and juice, the following foods may contain it at maximum levels of “10-2000 mg/kg”:

  • A variety of fresh, peeled, cut and shredded, frozen, and dried fruits and vegetables are available
  • Mermelades, jams, and jellies
  • Dry biscuits

The JECFA has also approved it as an antioxidant and preservative with an acceptable daily intake of “0-0.7 mg/kg body weight” established in 1998.

Sodium metabisulfite vs potassium metabisulfite

Sodium metabisulfite and potassium metabisulfite both have a number of uses in the food and beverage industry, but there are some differences between them.

Sodium metabisulfite is often used for its preservative properties, while potassium metabisulfite acts as a stabilizer. Sodium metabisulfite is also used to bleach flour and clarify beer, while potassium metabisulfite is not effective for these purposes.

Sodium Metabisulfite

Sodium metabisulfite is a white salt that dissolves readily in water and has very low solubility in alcohols. It’s used as a preservative in wine, beer, cider, and liqueurs as well as non-alcoholic beverages like juices and soft drinks. Sodium metabisulfite is also used to bleach flour and clarify beer by removing proteins from the liquid. The chemical name for sodium metabisulfite is sodium 4,4′-disulfanediylbis[sodium bis(sulfite)], but it’s most commonly referred to by its common name: “sodium bisulphite.”

Potassium Metabisulfite

Potassium metabisulfite isn’t used as much as sodium metabisulfite, but it’s still an important preservative in the food and beverage industry. It’s often used when making wine because it doesn’t interfere with fermentation like sodium metabisulfite does. Potassium metabisulfite is also used to prevent browning in food products like apples and potatoes.

What are the side effects of potassium metabisulfite?

Potassium metabisulfite is generally considered to be safe. It has been used as a preservative in food and beverages for many years, including in wine and beer. Potassium metabisulfite can cause some side effects in people who are sensitive to sulfites. Side effects of potassium metabisulfite include:

Skin rashes. The sulfite content of potassium metabisulfite is high enough to cause skin rashes in some people. This can be especially problematic for those who are allergic to sulfites and have asthma. Skin rashes may also occur when you use large amounts of the product at once.

Allergic reactions. Some people experience allergic reactions to potassium metabisulfite, including mild symptoms such as hives (itchy bumps) and swelling on the skin. Severe allergic reactions, called anaphylaxis, can be life-threatening and require emergency medical attention if they occur — tell your doctor if you have had a severe allergic reaction to this ingredient or any other food or medicine before using it again

Asthma attacks. People with asthma who use potassium metabisulfite may experience breathing problems due to an asthma attack caused by sulfites; however, this is rare

Cancer. The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), has found that there’s no evidence that potassium metabisulfite causes cancer in humans, although limited evidence indicates that it might cause cancer in animals

Where to buy potassium metabisulfite?

Potassium metabisulfite can be found in many grocery stores, but you may not know that it goes by other names. It is also called potassium bisulfite and potassium hydrogen sulfate. You can find it in the food preservation aisle at the grocery store or in the pharmacy section, where it is used as a preservative in medications.

You can also purchase this chemical online. The best place to shop for it is on Amazon because they have a wide selection of options and prices that are competitive with other online retailers.

If you’re looking to buy potassium metabisulfite powder in a large quantity, you can purchase it from Grade Chemical, which is one reliable potassium metabisulfite supplier in China. for their Potassium metabisulfite price is much more competitive than local market prices.

Frequently asked questions

Is potassium metabisulfite natural?

Yes, potassium metabisulfite is natural. It is also known as potassium bisulfite and is a chemical compound that occurs naturally in fruits, vegetables, and other foods. It can be found in wine, cider, beer, and some mineral waters. Potassium metabisulfite is also added to foods as a preservative or antioxidant.

Is potassium metabisulfite vegan?

Yes, potassium metabisulfite is vegan. Potassium metabisulfite is an antimicrobial and preservative that is most often used in wine-making, but it can also be found in some food products. Unlike sulfur dioxide—which is used to preserve dried fruits and some wines—potassium metabisulfite does not contain any animal products.

Is potassium metabisulfite bad for you?

No, potassium metabisulfite is not bad for you. It is a chemical compound that is used as a preservative and antioxidant in food. It has been approved by the U.S. Food and Drug Administration (FDA) and the European Union’s Scientific Committee on Food, which both consider it safe for human consumption.

Is potassium metabisulfite used as a food preservative?

Yes, potassium metabisulfite is used as a food preservative. It is often used to preserve wines and beers, especially those that are sold in bulk. It also has the ability to kill yeast cells, so it’s useful for killing off the yeast in wine that has been bottled and stored for too long.


As you can see, potassium metabisulfite is used for a wide range of processes. It’s an effective antiseptic, a preservative, and a bleaching agent. It’s been used as such in foods and wine for decades without a problem. Potassium metabisulfite side effects are mild or absent when consumed within the approved dosage and represent no danger to humans.

If you have any questions or inquiries about potassium metabisulfite? please contact us in the below comments.

Sophie Feng

Sophie Feng

Sophie Feng is the author of gradechemical.com, she is the co-founder of the grade chemical network. She has been in grade chemical company since 2017, with a working knowledge of food chemical .

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