E331 – Sodium Citrates: Function, Safety & Uses
E331 refers to sodium citrates, salts of citric acid used as food additives for acidifying, buffering, and stabilizing a wide range of food products.
Things worth knowing about "E331"
E331 refers to sodium citrates, salts of citric acid used as food additives for acidifying, buffering, and stabilizing a wide range of food products.
What is E331?
E331 is the EU designation for sodium citrates – salts of citric acid (E330) produced by neutralizing citric acid with sodium hydroxide or sodium carbonate. The code E331 covers three related compounds:
- E331(i) – Monosodium citrate
- E331(ii) – Disodium citrate
- E331(iii) – Trisodium citrate
All three forms appear as white, odourless crystals or powders that dissolve readily in water. They are widely used in the food industry, pharmaceuticals, and medicine.
Function as a Food Additive
Sodium citrates serve several technological functions in food products:
- Acidity regulator: They impart a mildly acidic, fresh taste to products.
- Buffering agent: They stabilize the pH level in foods, preventing unwanted acidic or alkaline shifts.
- Emulsifying salt: Trisodium citrate in particular is used in processed cheese to disperse proteins and create a smooth, uniform texture.
- Stabilizer and preservative aid: Sodium citrates inhibit the growth of certain microorganisms, thereby extending shelf life.
- Sequestrant (chelating agent): They bind metal ions such as calcium and iron, slowing the oxidation of fats.
Occurrence in Foods
E331 can be found in a wide variety of processed foods, including:
- Processed cheese and cheese products
- Soft drinks and sports drinks
- Jams, jellies, and marmalades
- Desserts, puddings, and ice cream
- Ready meals and soups
- Infant food (within approved limits)
Medical and Pharmaceutical Applications
Sodium citrates also play an important role outside the food industry:
- Antacid and urinary alkalizer: Trisodium citrate is used as a medication to treat urinary tract infections and to alkalinize urine. It raises urinary pH, which inhibits the growth of certain bacteria and helps dissolve uric acid crystals.
- Anticoagulant: In blood banking and laboratory medicine, sodium citrate is used as an anticoagulant for blood samples, as it binds calcium ions that are essential for blood clotting.
- Electrolyte solution: It is an ingredient in oral rehydration solutions used to treat diarrhoea and dehydration.
- Buffering agent in pharmaceuticals: Sodium citrate stabilizes pH levels in liquid medications and injectable solutions.
Safety and Health Assessment
Sodium citrates are considered safe and well-tolerated food additives. The European Food Safety Authority (EFSA) has classified E331 as safe and has not established a numerical ADI (Acceptable Daily Intake), as no harmful effects are known at normal consumption levels.
Citric acid and its salts occur naturally in the human body as intermediates in the citric acid cycle (Krebs cycle). The body therefore metabolizes ingested sodium citrates without difficulty.
Individuals who must follow a low-sodium diet (e.g., due to high blood pressure or kidney disease) should be aware of the sodium contribution from additives such as E331, although the overall contribution to total sodium intake is generally small.
Labelling and Regulation
In the European Union, E331 is authorized under Regulation (EC) No. 1333/2008 on food additives. Products must declare it either as E331 or as sodium citrates. For most food categories, the principle of quantum satis applies (used at the level necessary to achieve the intended technical effect). Specific quantity limits apply to certain categories such as infant foods.
References
- European Food Safety Authority (EFSA): Scientific Opinion on the re-evaluation of citric acid (E 330) and sodium, potassium, calcium and ammonium citrates (E 331, E 332, E 333) as food additives. EFSA Journal, 2014;12(6):3700.
- European Parliament and Council of the European Union: Regulation (EC) No. 1333/2008 on food additives. Official Journal of the European Union, 2008.
- Biesalski, H.K. et al.: Nutritional Medicine. 5th Edition. Georg Thieme Verlag, Stuttgart, 2018.
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