Sulfur dioxide belongs to the sulfite equilibrium system
E220 sulfur dioxide is part of the sulfur dioxide-sulfite family that includes sulfite, bisulfite and metabisulfite salts. In foods and in the body, sulfur dioxide, bisulfite and sulfite exist in equilibria influenced by pH. EFSA considered read-across between sulfite sources possible based on their capacity to form sulfite ions, while also noting uncertainty about reactions in different foods and the products formed. A food file should therefore express use and exposure as SO2 equivalents where required.
E220 is used for antioxidant, antibrowning and antimicrobial functions. It can inhibit yeasts, moulds and bacteria, protect colour, prevent enzymatic and non-enzymatic browning, and preserve aroma in some products. Common contexts include wine, dried fruits, fruit preparations, crustaceans and some processed vegetables where permitted. Its effectiveness and risks depend on pH, binding reactions and free versus bound SO2.
Free SO2, bound SO2 and food matrix
In wine and acidic fruit systems, free molecular SO2 is the most antimicrobial fraction, and its level depends strongly on pH. A lower pH gives more molecular SO2 at the same free sulfite concentration. Sulfites also bind carbonyl compounds, sugars and other food constituents, reducing the free active fraction. Total sulfite is therefore not the same as active protection. A product may have high total SO2 but insufficient free SO2 for microbial control.
Because sulfites react with foods, product-specific testing is essential. Dried fruits need colour and browning protection; wine needs microbial and oxidation management; crustaceans need melanosis control. Each matrix binds sulfite differently and has different label thresholds and consumer expectations.
EFSA update and sensitivity
EFSA's 2016 re-evaluation kept a temporary group ADI of 0.7 mg SO2 equivalents/kg body weight per day and found exposure estimates above that ADI for all population groups. In 2022, EFSA's follow-up concluded that new data did not address the gaps and that the database was insufficient to establish an ADI, leading to withdrawal of the temporary ADI. EFSA's 2025 exposure update further reflects ongoing risk-management work. Current technical files should therefore treat sulfites as high-attention additives.
Sulfites can trigger sensitivity reactions in susceptible individuals, especially some people with asthma. Labelling and threshold rules are critical. Even when technologically justified, E220 must be controlled for allergen-style communication and residual level.
Quality and release
Quality control should include source identity, SO2 equivalent calculation, addition point, pH, free SO2, total SO2 where relevant, residual level and label review. For wine, monitor free and total SO2 through storage. For dried fruit, monitor residual sulfite and colour. For products using sulfites as antibrowning agents, test colour, flavour and residual level at end of life. E220 is powerful, but its reactive chemistry means dose, binding and labelling must all be controlled.
Minimum effective dose
Minimum effective dose should balance microbial or browning control with residual sulfite and sensory impact. Because EFSA withdrew the temporary ADI and sulfites can affect sensitive consumers, unnecessary overuse should be avoided. Measure residual level, not just addition amount.
Application examples
In wine, sulfur dioxide management depends on pH, free SO2, total SO2, oxygen exposure and microbial target. In dried fruit, the goal may be colour retention and microbial control, but residual level and label threshold are critical. In crustaceans, sulfites can control melanosis, yet residues and consumer sensitivity must be managed. In fruit preparations, sulfite can prevent browning but may react with pigments, flavours and carbonyl compounds. Each use requires matrix-specific residual testing.
Analytical release
Analytical release should include SO2-equivalent addition, free SO2 and total SO2 where relevant, pH, residual level at end of life, label declaration and sensory impact. In wine, free molecular SO2 is tied to pH and is more meaningful than total SO2 alone. In dried fruit, residual sulfite after storage is more relevant than addition amount. E220 is reactive, so release must measure what remains and what is active.
Investigation logic
If browning occurs, check residual free SO2, oxygen exposure, enzyme activity and package. If microbial spoilage occurs, check pH and free molecular SO2. If consumers report sensitivity, check residual level and labelling. If sulfur notes appear, check dose and binding. Sulfur dioxide is powerful but requires careful residual and allergen-style control.
Supplier change
Supplier change should include SO2-equivalent strength, impurity profile, dosing equipment compatibility and storage stability. Gas, solution and salt-derived sulfite systems behave differently in handling. A change in source can alter dosing accuracy and residual levels.
Operator control
Operators should control ventilation, dosing, pH and residual testing. Sulfur dioxide is reactive and volatile, so addition amount alone is not enough. The release decision should be based on measured residual and label threshold, not only on the recipe.
Label and claim control
Label and claim control is central for sulfites because sensitive consumers depend on accurate declaration. The product file should state residual level, threshold basis, analytical method and market-specific wording. A process that removes some sulfite still needs proof before omitting declaration.
Storage release
Storage release should measure residual sulfite at the point consumers receive the product. Binding and volatilization can change the active fraction between production and sale.
Release logic for Food Additive E220 Sulfur Dioxide
Food Additive E220 Sulfur Dioxide needs a narrower technical lens in Food Additives E Codes: ingredient identity, process history, analytical method, storage condition and release decision. This is where the article moves from naming the subject to explaining which variable should be controlled, why that variable moves and what would make the evidence unreliable.
The source list for Food Additive E220 Sulfur Dioxide is strongest when each citation has a job. Re-evaluation of sulfur dioxide-sulfites (E 220-228) supports the scientific basis, Follow-up of the re-evaluation of sulfur dioxide and sulfites (E 220-228) supports the processing or quality angle, and Update of dietary exposure to sulfur dioxide and sulfites with alternative maximum levels helps prevent the article from relying on a single method or a single product matrix.
This Food Additive E220 Sulfur Dioxide page should help the reader decide what to do next. If unexplained variation, weak release logic, complaint recurrence or poor transfer from trial to production is observed, the strongest response is to confirm the mechanism, protect the lot from premature release and adjust only the variable supported by the evidence.
Additive E220 Sulfur Dioxide: additive-function specification
Food Additive E220 Sulfur Dioxide should be handled through additive identity, purity, legal food category, maximum permitted level, carry-over, matrix compatibility, declaration and technological function. Those words are not filler; they define the evidence that proves whether the product, lot or process is still inside its intended control boundary.
For Food Additive E220 Sulfur Dioxide, the decision boundary is dose approval, label check, market restriction, substitute selection or supplier requalification. The reviewer should trace that boundary to assay, purity statement, formulation dose calculation, finished-product check, label review and matrix performance test, then record why those data are sufficient for this exact product and title.
In Food Additive E220 Sulfur Dioxide, the failure statement should name wrong additive class, excessive dose, weak function, regulatory mismatch, undeclared carry-over or poor compatibility with pH and heat history. The follow-up record should preserve sample point, method condition, lot identity, storage age and corrective action so another reviewer can repeat the conclusion.
FAQ
What does sulfur dioxide do in foods?
It acts as antioxidant, antibrowning agent and antimicrobial preservative in selected permitted products.
What changed in EFSA's sulfite assessment?
EFSA withdrew the temporary group ADI in 2022 because the database was insufficient to establish an ADI.
Sources
- Re-evaluation of sulfur dioxide-sulfites (E 220-228)EFSA opinion used for sulfite equilibria, temporary group ADI and exposure exceedance context.
- Follow-up of the re-evaluation of sulfur dioxide and sulfites (E 220-228)EFSA follow-up used for withdrawal of the temporary ADI due to insufficient toxicological data.
- Update of dietary exposure to sulfur dioxide and sulfites with alternative maximum levelsEFSA 2025 technical report used for current exposure-update context.
- Plain-language summary: follow-up of the re-evaluation of sulfur dioxide and sulfitesEFSA summary used for food-use functions and consumer-facing risk context.
- PubChem: Sulfur DioxideOpen chemical database used for sulfur dioxide identity and gas chemistry.
- Status, Antimicrobial Mechanism, and Regulation of Natural Preservatives in Livestock Food SystemsOpen-access review used for preservative mechanisms, food matrices and regulatory context.
- Food additivesEFSA overview used for food-additive authorisation, specifications and safety-assessment context.
- Codex General Standard for Food Additives Online DatabaseCodex database used for food categories, functional classes and additive-use context.