Sulfites and Food Additives: Uses and Risks

Posted on Feb 7, 2025 in Chemistry

Sulfites (E-220 to E-228): Uses and Risks

Sulfites are a group of food additives commonly used for their preservative and antioxidant properties. They include:

  • E-220 Sulfur dioxide (SO2)
  • E-221 Sodium sulfite (Na2SO3)
  • E-222 Sodium hydrogen sulfite (sodium bisulfite) (NaHSO3)
  • E-223 Sodium metabisulfite (sodium pyrosulfite) (Na2S2O5)
  • E-224 Potassium metabisulfite (potassium pyrosulfite) (K2S2O5)
  • E-226 Calcium sulfite (CaSO3)
  • E-227 Calcium hydrogen sulfite (calcium bisulfite) (Ca(HSO3)2)
  • E-228 Potassium hydrogen sulfite (potassium bisulfite) (KHSO3)

Structure, Properties, and Procurement

Sulfites occur naturally in many foods. As an additive, sulfur dioxide is self-limiting; exceeding a certain dose alters the product’s taste. It’s effective in an acidic environment, inhibiting bacteria and molds (and, to a lesser extent, yeasts). It destroys vitamin B1 but protects some vitamin C.

During cooking or industrial food processing, sulfur dioxide and sulfites are partially lost through evaporation or by combining with other components. Legal limits are always expressed in terms of sulfur dioxide. Sulfites act as antioxidants.

SO2 is prepared by reacting sulfur with O2. Sulfites are prepared by reacting sulfur dioxide with water and bases.

Uses of Sulfites

  • As a preservative: Grape juice, wine, cider, vinegar, and mustard sauce.
  • As an antioxidant: Canned vegetables, table olives, cephalopods, crustaceans, frozen juices, and beer.
  • In some countries, it’s used to preserve the fresh appearance of salad vegetables.
  • It can also be used to improve the appearance of meat, giving the impression of greater freshness. However, this practice is considered fraud and is forbidden in Spain.

Ingested sulfites are transformed into sulfates by enzymes.

Risks of Sulfites

  • In sensitive individuals (asthmatics): May cause reactions.
  • Diarrhea can result if gastric acid is insufficient.
  • It is not teratogenic.

There’s been discussion about replacing sulfites with other additives. This is impossible in the case of wine and may be possible when used as antioxidants.

Sodium Chloride (NaCl): Common Salt

Sodium chloride (common salt) is the most used substance among all food additives. It is not legally considered an additive in most cases and, except in exceptional circumstances, its use is not limited. It’s used as a condiment and preservative. Doses greater than 100g can cause death. There’s a dubious relationship between hypertension and salt intake; hypertensive patients are often advised to restrict salt.

What is a Food Additive?

In Spain, food additives are legally considered substances intentionally added to food to improve its physical properties, flavor, preservation, etc., but not those introduced to increase its nutritional value. If the added substance is removed, or if the amount in the food has no functional role, it’s not considered an additive but a processing aid.

Characteristics of Food Additives

  1. Health Requirements: A toxicological evaluation of the additive is required.
  2. Intended Use: Qualitative and quantitative information must be known.
  3. Technological Requirements: Justification for its use must be provided.
  4. Limitations: Subject to limitations on the amounts that can be used in certain foods.

In EU countries, food additives are designated by a code number consisting of the letter ‘E’ followed by three or four digits. They are classified as:

  • Colors: E-100 to E-180
  • Preservatives: E-200 to E-296
  • Antioxidants: E-300 to E-343
  • Emulsifiers and Stabilizers: E-4xx
  • Sweeteners: E-4xx and E-9xx
  • Other: E-2xx, E-3xx, E-5xx, E-6xx, and E-7xx, including alkalis (bases), acidifiers, anticaking agents, and flavor enhancers.

Reasons for Using Food Additives

  1. Economic and Social Reasons:
    • Prolong the shelf life of food.
    • Increase access to food for consumers.
    • Utilize surplus food.
  2. Health Reasons:
    • Ensure the sanitary quality of the final product.
    • Prevent the transmission of foodborne diseases (function of preservatives).
  3. Physiological Reasons:
    • Improve the digestibility of food (e.g., yeast in bread).
    • Allow the removal of certain components, making food suitable for specific risk groups (e.g., decaffeinated coffee).
  4. Technological Reasons:
    • Improve the presentation of a product to make it more appealing (e.g., colors).
    • Achieve diversification at the industrial level, resulting in a wider range of food products.