E-numbers / Thickeners & emulsifiers / E402
also: Potassium salt of alginic acid
A natural thickener and stabiliser made from seaweed, used to give foods a smooth, gel-like texture.
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Potassium alginate is the potassium salt of alginic acid, a naturally occurring polysaccharide extracted from brown seaweed (kelp and related species).
Potassium alginate is the potassium salt of alginic acid, a naturally occurring polysaccharide extracted from brown seaweed (kelp and related species). It forms a thick, viscous solution or soft gel when dissolved in water, and has been used as a food ingredient for decades.
It absorbs water and swells to create a gel or thick, stable texture. It works by binding with water molecules and, in some formulations, with calcium ions to form a firmer gel. This makes it useful as a thickener, stabiliser, and emulsifier that stops ingredients separating or breaking down during storage.
Found in dairy desserts, ice cream, salad dressings, fruit fillings, sauces, restructured meat and fish products, and some low-fat spreads. On the label it appears as 'potassium alginate' or 'E402'.
Potassium alginate is not digested by human gut enzymes. It passes through the digestive tract largely intact, acting in a similar way to soluble dietary fibre. It is not absorbed into the bloodstream in meaningful quantities at the amounts present in food.
Alginic acid and its salts, including potassium alginate, are not digested by human digestive enzymes and are not absorbed to any significant extent from the gastrointestinal tract.
EFSA reviewed all available toxicology data on alginates in 2017 as part of a systematic re-evaluation of permitted food additives. The panel found no safety concern at the exposure levels arising from authorised uses and concluded that no numerical acceptable daily intake was necessary. This conclusion followed an earlier JECFA assessment that had reached the same outcome.
The EFSA ANS Panel concluded there was no safety concern at the refined exposure estimates for authorised uses of potassium alginate (E402) as a food additive, and that a numerical ADI was not necessary.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) previously assigned an ADI 'not specified' to alginic acid and its salts, indicating no numerical limit was considered necessary at typical food use levels.
Animal studies using doses far above any realistic dietary exposure found loose stools and reduced mineral absorption at very high intake levels. These effects are a consequence of the high-fibre bulk behaviour of alginates, not a toxic mechanism, and are not considered relevant to the amounts present in food.
Rats fed very high doses of alginates showed soft stools and reduced absorption of some minerals; no adverse effects were observed at lower doses consistent with realistic dietary exposure from food use.
People on a potassium-restricted diet (for example, those with chronic kidney disease who are advised to limit potassium intake) should be aware that potassium alginate contributes a small amount of potassium. Look for 'potassium alginate' or 'E402' on the label. Those with seaweed or iodine sensitivity may also wish to note its seaweed origin, though processing removes most of the iodine content.
Potassium alginate is one of the more straightforwardly ordinary additives on the approved list. It comes from seaweed, it behaves like soluble fibre in the body, and two separate international regulatory reviews decades apart reached the same conclusion: no numerical intake limit is needed. There is no credible published evidence linking it to harm at the amounts found in food. The only realistic point of attention is its potassium content for people actively managing potassium intake under medical advice.
No. Potassium alginate (E402) is approved for use in food in both the UK and the EU under assimilated Regulation 1333/2008. It appears on the UK FSA's list of permitted food additives.
Potassium alginate is derived from brown seaweed, which naturally contains iodine. However, the extraction and purification process removes the vast majority of iodine from the finished additive. It is not considered a meaningful source of dietary iodine.
Potassium alginate is used in dairy desserts, ice cream, salad dressings, fruit fillings, restructured meat and fish products, and some low-fat spreads. Check the ingredients list for 'potassium alginate' or 'E402'.
Yes. Potassium alginate is derived entirely from brown seaweed and contains no animal-derived ingredients, making it suitable for vegan and vegetarian diets.
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