E402 - Potassium alginate

At a glance

• What it is: The potassium salt of alginic acid from brown seaweed; a plant‑based, vegan additive
• What it does: Thickens, stabilises, gels with calcium, helps emulsions stay mixed, and holds water
• Typical uses: Fruit fillings, sauces, dairy and plant‑based desserts, restructured foods, and “spherification” in modernist cooking
• Label names: “Potassium alginate” or “E402” (EU); “potassium alginate” (U.S.)
• Allergen status: Not a common allergen; it’s a carbohydrate, not a protein
• Dietary notes: Gluten‑free and suitable for vegetarians and vegans
• Regulatory status: Approved in the EU and considered GRAS (generally recognized as safe) in the U.S. when used as intended

Why is Potassium alginate added to food?

Food makers use potassium alginate to manage texture and stability. It thickens liquids without adding much taste, helps sauces and dressings stay uniform, limits water weeping (syneresis) in pies and desserts, and stabilises foams. In the presence of calcium ions, it forms a firm, flexible gel—useful for setting shapes, encapsulating flavors, and making pearls or “spheres” in culinary applications.

What foods contain Potassium alginate?

You’ll most often find E402 in:

• Fruit preparations and pie fillings
• Ice cream, sorbets, and plant‑based frozen desserts
• Flavoured milk and plant‑based drinks
• Spoonable and drinkable yogurts and fermented dairy alternatives
• Salad dressings, sauces, and condiments
• Reformed or restructured foods (for example, shaped seafood or meat analogues)
• Confectionery gels and modernist “spherification” recipes (often with a calcium salt like calcium chloride)

Potassium alginate is part of the alginate family alongside alginic acid, calcium alginate, and propylene glycol alginate.

What can replace Potassium alginate?

Alternatives depend on the job you need done:

• Thickening and stabilising: xanthan gum, guar gum, locust bean gum, carrageenan, or pectins
• Gelling: agar or carrageenan; note each gel behaves differently
• For spherification‑style gels, alginates are unique; you typically need an alginate plus a calcium source. If potassium alginate isn’t available, another alginate grade may be used with recipe adjustments.

How is Potassium alginate made?

Manufacturers extract alginates from brown seaweeds. The seaweed is treated with an alkaline solution to pull out the alginate, solids are removed, and the alginate is precipitated as alginic acid. This alginic acid is then neutralised with a potassium base (such as potassium carbonate or hydroxide) to form potassium alginate, which is washed, dried, and milled to a fine powder.¹

Is Potassium alginate safe to eat?

Yes. The European Food Safety Authority (EFSA) re‑evaluated alginic acid and its salts (E 400–E 404) and found no safety concern at reported uses and levels; an Acceptable Daily Intake (ADI) “not specified” was assigned for the group.² In the United States, the Food and Drug Administration (FDA) lists potassium alginate as GRAS (generally recognized as safe) when used in line with good manufacturing practice.³

Alginates are large carbohydrates that are not meaningfully digested or absorbed; most passes through the gut, and very high intakes may cause mild gastrointestinal effects such as gas or stool changes in sensitive individuals.²

Does Potassium alginate have any benefits?

From a culinary and manufacturing standpoint, it offers several:

• Creates smooth, stable textures in dressings and desserts
• Forms flexible, heat‑tolerant gels with calcium for shaping or encapsulation
• Helps retain moisture and reduce weeping in fillings and gels

These are technological benefits; potassium alginate is not used as a nutrient.

Who should avoid Potassium alginate?

• People on potassium‑restricted diets (for example, some with chronic kidney disease) may need to manage all sources of potassium. While the potassium contribution from E402 is usually small, ask a healthcare professional if you must limit dietary potassium.⁴
• Infants and very young children: EFSA highlighted limited data for very young infants and recommended careful, specific regulation of uses in foods for infants and young children; products in these categories have their own rules.²
• Anyone who notices digestive discomfort with alginates should reduce intake and check labels.

Myths & facts

• Myth: “E402 is synthetic and petroleum‑based.” Fact: Potassium alginate is derived from seaweed.
• Myth: “All alginates are identical.” Fact: Different alginate salts (potassium, calcium, etc.) behave differently in recipes and processing.
• Myth: “It gels on its own.” Fact: Alginate gels need calcium ions to set.
• Myth: “It’s a source of iodine.” Fact: Food‑grade potassium alginate is a purified carbohydrate; iodine is largely removed during processing.

Potassium alginate in branded foods

On EU labels, additives must appear by function (for example, “thickener”) followed by the name or E‑number—so you might see “thickener: potassium alginate (E402).”⁵ In the U.S., ingredients are listed by their common or usual names, so look for “potassium alginate.”⁶

You’ll commonly see it in fruit‑on‑the‑bottom yogurts, pie fillings, ice creams and sorbets, creamy dressings, flavoured milks or plant‑based beverages, and in chef‑driven products that use spherification. Formulas change, so check the ingredient list to be sure.

References

Footnotes

1. Alginates (INS 400–405) — FAO/WHO JECFA Specifications. https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-additives/en/ ↩

2. Re‑evaluation of alginic acid and its salts (E 400–E 404) as food additives — EFSA (European Food Safety Authority). https://www.efsa.europa.eu/en/efsajournal/pub/5049 ↩ ↩² ↩³

3. Food Additive Status List — FDA (U.S. Food and Drug Administration). https://www.fda.gov/food/food-additives-petitions/food-additive-status-list ↩

4. Potassium in diet — MedlinePlus, NIH. https://medlineplus.gov/ency/article/002413.htm ↩

5. Regulation (EU) No 1169/2011 on the provision of food information to consumers — EUR-Lex. https://eur-lex.europa.eu/eli/reg/2011/1169/oj ↩

6. Ingredient labeling; declaration of ingredients (21 CFR 101.4) — eCFR, FDA. https://www.ecfr.gov/current/title-21/part-101#p-101.4 ↩