E-numbers / Other additives / E511
also: MgCl2 · Nigari
A magnesium salt used as a firming agent and mineral supplement, best known for setting tofu from soy milk.
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Chickpeas, Water, Sugar, Salt, Firming Agent (Calcium Chloride, Magnesium Chloride), Rapeseed Oil, Spices, Chilli, Corn Starch, Spice Extracts
Magnesium chloride is the magnesium salt of hydrochloric acid.
76
of the 43,325 UK supermarket foods we checked declare E511 in their ingredients
That is 0.2%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Magnesium chloride is the magnesium salt of hydrochloric acid. It occurs naturally in seawater and is commercially extracted from brines, seawater evaporation, or mineral deposits. In food use it is typically a white crystalline powder or flake, highly soluble in water.
In food manufacturing it acts as a firming agent: magnesium ions cross-link proteins, causing them to solidify or gel. In tofu production (as nigari, the traditional Japanese coagulant) it causes soy proteins to coagulate and separate from the whey liquid. It is also used as a source of magnesium for nutritional fortification, and can function as a colour-retention agent and processing aid in some applications.
Most commonly in tofu (where it appears as nigari or listed as magnesium chloride in the coagulant declaration), mineral water products, sports drinks and nutritional supplements formulated with added magnesium. Also used in some infant formula, certain cheeses, and processing of some canned vegetables to maintain firmness. On a UK label it appears as 'magnesium chloride' or 'E511'.
Magnesium is an essential mineral required for hundreds of enzymatic reactions, including energy production, protein synthesis, nerve and muscle function, and bone formation. The UK Reference Nutrient Intake is 300mg per day for adult men and 270mg per day for adult women. The small amounts contributed by E511 as a food additive count toward total dietary magnesium intake, which most UK adults consume at adequate but not excessive levels.
Magnesium is an essential cofactor for over 300 enzymatic reactions and is required for DNA synthesis, protein synthesis, and normal muscle and nerve function.
The UK Reference Nutrient Intake for magnesium is 300mg per day for men and 270mg per day for women aged 19 and over.
At high supplemental doses, magnesium salts including magnesium chloride can cause osmotic diarrhoea because unabsorbed magnesium ions draw water into the intestine. This effect is well documented for magnesium supplements but the amounts present in food as E511 are far below the doses associated with this effect. The European Food Safety Authority set an upper tolerable intake level of 250mg per day for supplemental magnesium specifically to avoid this laxative threshold.
Supplemental magnesium at doses above 250mg per day is associated with diarrhoea due to osmotic effects in the gut; this is the basis for EFSA's tolerable upper intake level for supplemental magnesium.
People with kidney disease should be cautious about all supplemental magnesium sources, including fortified foods and drinks, as impaired kidneys struggle to excrete excess magnesium. People taking certain medications (tetracyclines, bisphosphonates) should note that magnesium can reduce their absorption if consumed at the same time. Look for 'magnesium chloride' or 'E511' in the ingredients list.
Magnesium chloride has been used in food for centuries, most visibly as the tofu coagulant nigari in East Asian cuisine. As a food additive it supplies the same magnesium ion found naturally in leafy greens, nuts, and wholegrains. The quantities used in food are well within normal dietary ranges. No regulatory body has raised a concern about its use in food at levels achieved through normal consumption. The laxative effect associated with magnesium supplements requires substantially higher doses than those contributed by E511 in food.
No. Magnesium chloride (E511) is approved for use in the UK under the FSA approved-additives list and assimilated EU Regulation 1333/2008. It is a long-established food additive with no current restrictions or bans.
Yes. Nigari is the traditional Japanese name for the bittern left after salt is extracted from seawater, which is predominantly magnesium chloride. It has been used to coagulate tofu for centuries. When used in commercially produced tofu sold in the UK, it may be declared as 'nigari', 'magnesium chloride', or 'E511' on the label.
Tofu is by far the most common source, where magnesium chloride acts as the coagulant that sets soy milk into a solid block. It also appears in some mineral waters, sports and electrolyte drinks, food supplements, infant formula, and some processed vegetables where it is used as a firming agent.
Yes. Magnesium chloride is derived from mineral sources such as seawater or brine deposits. It contains no animal-derived ingredients and is suitable for vegans and vegetarians. It is in fact the coagulant of choice in much vegan cooking, being used to make tofu.
Last reviewed: 20 June 2026
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