Ammonium alginate
A seaweed-derived thickener and gelling agent used to give foods a smooth, stable texture.
What is it?
Ammonium alginate is the ammonium salt of alginic acid, a natural polysaccharide extracted from brown seaweeds (principally Laminaria and Macrocystis species). It dissolves readily in cold water to form a viscous gel.
What does it do?
It thickens and stabilises liquid and semi-solid food systems by forming a gel network when hydrated. It prevents ingredients from separating, improves texture, and helps retain moisture during processing and storage.
Where you will see it
Used in desserts, ice cream and frozen confections, salad dressings, sauces, bakery fillings, and some processed dairy products. On a label it appears as 'ammonium alginate' or 'E403'.
What the science says
EFSA re-evaluation 2017
The European Food Safety Authority completed a full re-evaluation of alginic acid and all its food-grade salts, including the ammonium salt, in 2017. Reviewers examined toxicology, metabolism and dietary exposure data. They found no basis for a numerical acceptable daily intake and identified no safety concern at the levels used in food.
EFSA concluded there was no need for a numerical ADI and no safety concern for ammonium alginate (E403) at the levels of refined dietary exposure assessed for its use as a food additive.
Digestive fate
Alginates are not broken down or absorbed in the human small intestine. They pass into the large bowel where gut bacteria partially ferment them, similarly to other soluble dietary fibres. The ammonium counterion contributes negligible additional nitrogen at typical food-use levels.
Alginic acid and its salts are not digestible in the upper gastrointestinal tract and are fermented to varying degrees by colonic microbiota, consistent with behaviour of non-digestible polysaccharides.
Genotoxicity and long-term toxicity
Standard battery genotoxicity tests on alginate salts have been negative. Long-term and reproductive toxicity studies conducted on the alginate family did not reveal adverse effects at dietary concentrations. EFSA found the available database adequate to draw conclusions without requiring new studies.
No genotoxic or carcinogenic potential was identified for alginic acid and its salts in the studies reviewed during the 2017 EFSA re-evaluation.
Where it stands with the regulators
Who should be careful
No specific group is required by law to avoid ammonium alginate. People following seaweed-free diets for personal or medical reasons may wish to note it is seaweed-derived. Look for 'ammonium alginate' or 'E403' on the label.
The honest read
Ammonium alginate belongs to a family of seaweed-derived gelling agents that have been in the food supply for many decades and have been subject to a thorough modern re-evaluation. The regulatory science is settled: no numerical intake limit was deemed necessary. There is no active scientific debate about harm at the levels found in food.
Related additives
Common questions
Is E403 banned in the UK?
No. Ammonium alginate is on the UK FSA's approved additives list and is authorised under assimilated EU Regulation 1333/2008. It remains permitted for use in food.
Is ammonium alginate the same as MSG or other controversial additives?
No. It is a seaweed-derived thickener with no relationship to glutamates or synthetic flavour compounds. It has no hyperactivity association and carries no mandatory warning label.
What foods contain E403?
Most commonly found in ice cream, frozen desserts, salad dressings, sauces, bakery fillings, and some processed dairy products. It is listed as 'ammonium alginate' or 'E403' in the ingredients.
Is E403 vegan?
Yes. Ammonium alginate is derived from brown seaweed and contains no animal-derived ingredients. It is suitable for vegan and vegetarian diets.
Sources
- EFSA re-evaluation of alginic acid and its sodium, potassium, ammonium and calcium salts (E400-E404) as food additives - EFSA Journal 2017;15(10):5049
- Ammonium alginate (E403) - UK FSA authorised regulated food products register
- Approved additives and E numbers - Food Standards Agency
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