E222 (Sodium hydrogen sulphite) is a chemical compound that belongs to the sulphite group, sulphur-based components that release sulphur dioxide SO2, an active preservative compound.

It appears as white powder.

Sodium bisulfite

(Chemical name: sodium hydrogen sulfite; formula: NaHSO₃)

Description

Sodium bisulfite (NaHSO₃) is an inorganic salt used primarily as an antioxidant, preservative, and anti-browning agent in food processing.
In solution, it releases sulfur dioxide (SO₂), responsible for its technological functions in controlling oxidation, slowing enzymatic browning, and inhibiting microbial growth.
It is typically supplied as white to yellowish crystals or granules, or as a concentrated aqueous solution.

Indicative nutritional values per 100 g

(Not applicable—sodium bisulfite is a food additive, not a nutrient.)

Key constituents

• NaHSO₃ (sodium hydrogen sulfite)

• May release:

  • SO₂ (active preservative component)

  • bisulfite ions and sulfite ions (depending on pH and solution chemistry)

Production process

1. Raw materials

   • Produced from sulfur dioxide (SO₂) and sodium carbonate or sodium hydroxide.

2. Synthesis

   • SO₂ is dissolved in a sodium carbonate/sodium hydroxide solution under controlled pH.

   • Reaction forms NaHSO₃.

3. Purification

   • Removal of impurities and excess SO₂.

4. Drying or concentration

   • Final product obtained as a crystal/powder or as an aqueous solution.

5. Packaging

   • Packed in moisture-proof containers to avoid oxidation and loss of SO₂ content.

Production follows GMP/HACCP and purity complies with food additive regulations.

Physical properties

• Appearance: white to yellowish crystalline powder or pellets

• Solubility: highly soluble in water

• Odour: characteristic sulfurous smell

• pH: acidic in solution

• Stability: decomposes slowly in air, releasing SO₂; heat accelerates breakdown

Sensory and technological properties

• Antioxidant: prevents oxidation in foods susceptible to browning.

• Anti-browning: inhibits polyphenol oxidase, preventing enzymatic browning in fruits/vegetables.

• Preservative: inhibits microbial growth, especially in low-acid products.

• Bleaching effect: mild bleaching action used in some processing steps.

• Color stabilizer: maintains color in dried fruits, seafood, cut potatoes, and some wines.

Food applications

• Beverages: wine, cider, fruit juices (as color stabilizer and antioxidant).

• Fruits & vegetables: dried fruits, cut potatoes, fresh-cut produce (anti-browning).

• Seafood: shrimp, lobster, crustaceans (prevents melanosis/black spot).

• Starches: prevents discoloration in potato products.

• Bakery products: dough conditioner in small quantities.

• Pickles & condiments: antioxidant and preservative.

Nutrition & health

• Not a nutrient; used only as a technological additive.

• In sensitive individuals (especially asthmatics), exposure to sulfites may cause:

  • bronchoconstriction

  • hives

  • digestive discomfort

These reactions depend on individual sensitivity and total sulfite intake from the diet.

Portion note

Not applicable. It is not consumed as a portion but as part of the formulation at very low concentrations.

Allergens & intolerances

• Sulfites are regulated allergens.

• Must be declared when present at ≥10 mg/kg or 10 mg/L (as total SO₂).

• Possible reactions in:

  • sulfite-sensitive individuals

  • asthmatics

• Does not contain gluten, lactose, or other major allergens unless introduced by cross-contamination.

Storage & shelf-life

• Store in cool, dry conditions, tightly closed.

• Sensitive to air and moisture.

• Shelf-life typically 12–36 months, depending on packaging.

• Aqueous solutions lose activity over time due to oxidation.

Safety & regulatory

• Approved as a food additive (E222 in EU).

• Maximum permitted levels vary by food category.

• Functions: antioxidant, preservative, color stabilizer.

• Regulatory considerations include:

  • declaration of sulfites on the label

  • limits on total SO₂

  • compliance with GMP/HACCP

• Excess SO₂ can cause sensory defects or regulatory non-compliance.

Labeling

May appear as:

• “sodium bisulfite”

• “sodium hydrogen sulfite”

• “E222”

• “sulfites” (when declaring allergens)

SO₂ content must be indicated when ≥10 mg/kg or L.

Troubleshooting

• Loss of activity: exposure to air/moisture → use airtight packaging.

• Off-odours (sulfurous): overuse or poor dispersion.

• Excessive bleaching: concentration too high → adjust dosage.

• Discoloration in solution: oxidation → prepare fresh solution; protect from air.

• Regulatory non-compliance: SO₂ above legal limits → verify dosing and testing.

Sustainability & supply chain

• Environmental considerations:

  • handling of SO₂ emissions,

  • proper wastewater treatment (monitored via BOD/COD),

  • controlled use to minimize over-sulfiting.

• By-products must be managed following chemical waste regulations.

Main INCI functions (cosmetics)

(as “Sodium Bisulfite”)

• Antioxidant

• Reducing agent

• Used to stabilise formulations containing sensitive ingredients.

Conclusion

Sodium bisulfite is an effective antioxidant, anti-browning agent and preservative, essential in many food processes where colour and microbial control are critical.
Used at appropriate levels and within regulatory limits, it ensures product stability, safety and visual quality.
Its use requires careful control due to regulatory limits and the potential for sensitivity to sulfites in certain individuals.

Mini-glossary

• SFA – Saturated fatty acids: not relevant for this ingredient.

• MUFA – Monounsaturated fatty acids: not relevant here.

• PUFA – Polyunsaturated fatty acids: not relevant here.

• TFA – Trans fatty acids: not relevant here.

• GMP/HACCP – Quality and safety management systems in food production.

• BOD/COD – Indicators of organic and chemical load in wastewater.

• SO₂ (Sulfur dioxide) – Active preservative released by sulfites.

• Sulfites – Group of additives used as antioxidants and preservatives; must be declared above regulated thresholds.

The sulphite group includes:

What it is used for and where

Food

Ingredient listed in the European food additives list as E222, preservative.

Safety

Symptoms attributable to sulphite sensitivity can be of varying nature and importance. The most common are headache and generalised itching or swelling, but cases of nausea, bronchoconstriction, diarrhoea, hypotension and shock have also occurred (1).

EFSA's Scientific Panel on Food Additives and Flavourings assessed the risk for toxic elements in sulphur dioxide (E 220-228), based on data submitted by stakeholders, and concluded that the EU specification maximum limits for arsenic, lead and mercury should be lowered and a maximum limit for cadmium should be introduced (2).

On the sulphite topic, the most relevant studies have been selected with a summary of their contents:

Sulphites studies

Molecular Formula      NaHO₃S

Molecular Weight      104.06

CAS  7631-90-5

UNII    TZX5469Z6I

EC Number   231-548-0

DSSTox ID  DTXSID8034902

IUPAC  sodium;hydrogen sulfite

InChl=1S/Na.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1

InChl Key      DWAQJAXMDSEUJJ-UHFFFAOYSA-M

SMILES  OS(=O)[O-].[Na+]

MDL number  MFCD00003530

PubChem Substance ID    24854644    329750172

ChEBI   26709

RTECS  UX8225000

NCI    C73837

ICSC    1134

NACRES  NA.21    

UN    3260    2693

Synonyms:

• Sodium bisulfite
• Sulfurous acid, sodium salt

References_____________________________________________________________________

(1) Gunnison AF, Jacobsen DW. Sulfite hypersensitivity. A critical review. CRC Crit Rev Toxicol. 1987;17(3):185-214. doi: 10.3109/10408448709071208. 

Abstract. Sulfiting agents (sulfur dioxide and the sodium and potassium salts of bisulfite, sulfite, and metabisulfite) are widely used as preservatives in foods, beverages, and pharmaceuticals. Within the past 5 years, there have been numerous reports of adverse reactions to sulfiting agents. This review presents a comprehensive compilation and discussion of reports describing reactions to ingested, inhaled, and parenterally administered sulfite. Sulfite hypersensitivity is usually, but not exclusively, found within the chronic asthmatic population. Although there is some disagreement on its prevalence, a number of studies have indicated that 5 to 10% of all chronic asthmatics are sulfite hypersensitive. This review also describes respiratory sulfur dioxide sensitivity which essentially all asthmatics experience. Possible mechanisms of sulfite hypersensitivity and sulfur dioxide sensitivity are discussed in detail. Sulfite metabolism and the role of sulfite oxidase in the detoxification of exogenous sulfite are reviewed in relationship to the etiology of sulfite hypersensitivity.

(2) EFSA Panel on Food Additives and Flavourings (FAF); Younes M, Aquilina G, Castle L, Engel KH, Fowler PJ, Frutos Fernandez MJ, Fürst P, Gundert-Remy U, Gürtler R, Husøy T, Manco M, Mennes W, Moldeus P, Passamonti S, Shah R, Waalkens-Berendsen I, Boon P, Cheyns K, Crebelli R, FitzGerald R, Lambré C, Mirat M, Ulbrich B, Vleminckx C, Mech A, Rincon AM, Tard A, Horvath Z, Wright M. Follow-up of the re-evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228). EFSA J. 2022 Nov 24;20(11):e07594. doi: 10.2903/j.efsa.2022.7594. 

Abstract. Sulfur dioxide-sulfites (E 220-228) were re-evaluated in 2016, resulting in the setting of a temporary ADI of 0.7 mg SO2 equivalents/kg bw per day. Following a European Commission call for data, the present follow-up opinion assesses data provided by interested business operators (IBOs) and additional evidence identified in the publicly available literature. No new biological or toxicological data addressing the data gaps described in the re-evaluation were submitted by IBOs. Taking into account data identified from the literature search, the Panel concluded that there was no substantial reduction in the uncertainties previously identified in the re-evaluation. Therefore, the Panel considered that the available toxicity database was inadequate to derive an ADI and withdrew the current temporary group acceptable daily intake (ADI). A margin of exposure (MOE) approach was considered appropriate to assess the risk for these food additives. A lower confidence limit of the benchmark dose of 38 mg SO2 equivalents/kg bw per day, which is lower than the previous reference point of 70 mg SO2 equivalents/kg bw per day, was estimated based on prolonged visual evoked potential latency. An assessment factor of 80 was applied for the assessment of the MoE. At the estimated dietary exposures, when using a refined exposure scenario (Data set D), MOEs at the maximum of 95th percentile ranges were below 80 for all population groups except for adolescents. The dietary exposures estimated using the maximum permitted levels would result in MOEs below 80 in all population groups at the maximum of the ranges of the mean, and for most of the population groups at both minimum and maximum of the ranges at the 95th percentile. The Panel concluded that this raises a safety concern for both dietary exposure scenarios. The Panel also performed a risk assessment for toxic elements present in sulfur dioxide-sulfites (E 220-228), based on data submitted by IBOs, and concluded that the maximum limits in the EU specifications for arsenic, lead and mercury should be lowered and a maximum limit for cadmium should be introduced.