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CAS Number: 7773-03-7
Synonyms: Potassium bisulfite, potassium hydrogen sulfite, E228, potassium pyrosulfite (related), sulphurous acid potassium salt (1:1), monopotassium sulfite
Physical Properties: White to off-white crystalline powder or granules with a pungent sulfur dioxide (SO₂) odor. Freely soluble in water (approx. 350 g/L at 20°C). Slightly soluble in ethanol. pH of 5% solution is 3.5–4.5. Unstable to heat, decomposes above 150°C releasing SO₂. Slowly oxidizes in air to potassium sulfate. Density 1.48 g/cm³.
Applications: Food preservative in wine, beer, fruit juices, cider, dried fruits (apricots, raisins, apples), dehydrated vegetables, jams, jellies, pickles, syrups, and seafood (shrimp, lobster). Also used as bleaching agent in sugar refining, dechlorination agent in water treatment, reducing agent in hair waving preparations, and in photographic developing solutions.
Description:
Potassium hydrogen sulphite (E228) is an inorganic sulfite salt that functions primarily as a reducing agent and broad-spectrum antimicrobial preservative through the controlled release of sulfur dioxide (SO₂) in aqueous acidic environments. The mechanism of action involves SO₂ disrupting microbial metabolism by reacting with disulfide bonds in essential enzymes, inhibiting their activity, and interfering with cofactors such as NAD⁺ and ATP synthesis. It also acts as a strong antioxidant by reacting with quinones and preventing both enzymatic and non-enzymatic browning reactions.
Compared to sodium metabisulfite (E223), potassium hydrogen sulphite contains no sodium, making it preferable for low-sodium food formulations. However, it is less stable than the metabisulfite form and has a more pronounced SO₂ odor when moist. In winemaking specifically, E228 is preferred over sodium salts because it introduces no excess sodium that could affect taste or fermentation kinetics. Its antioxidant properties preserve the color and flavor profile of white wines and prevent oxidative off-flavors such as acetaldehyde formation. In dried fruits, E228 retains the natural yellow-to-orange hue by inhibiting polyphenol oxidase (PPO).
Toxicologically, approximately one percent of asthmatic individuals experience hypersensitivity reactions to sulfites, which can include bronchospasm, urticaria, and in rare cases anaphylaxis. Consequently, the European Union mandates labeling of sulfite residues above 10 mg/kg. The acceptable daily intake (ADI) established by JECFA for all sulfites expressed as SO₂ is 0.7 mg per kilogram of body weight per day. Unlike nitrites which can form carcinogenic nitrosamines, sulfites do not generate significant carcinogenic residues, but they do destroy thiamine (vitamin B1), making them unsuitable for use in thiamine-rich foods such as meat and cereal products.
Despite its efficacy, consumer demand for "sulfite-free" products has increased due to allergy concerns, leading to alternative preservation technologies such as high-pressure processing (HPP) and ascorbic acid blends. E228 is banned or restricted in several countries, including the United States, where it is not listed as a direct food additive, although sulfiting agents are generally permitted with mandatory labeling for certain applications.
SAFETY INFORMATION ABOUT E228 – POTASSIUM HYDROGEN SULPHITE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
