What is E402?

Complete guide to understanding E402 (Potassium Alginate) in your food

The Quick Answer

E402 is potassium alginate, a natural thickener, stabilizer, and gelling agent derived from brown seaweed.

It’s used in food to create smooth textures, prevent ingredients from separating, and maintain consistency in reduced-sodium products.

Most people consume it multiple times per week in ice cream, yogurt, salad dressings, and other processed foods.

What Exactly Is It?

E402 is potassium alginate, the potassium salt of alginic acid, a naturally occurring polysaccharide found in brown seaweed.

Like E401 (sodium alginate), potassium alginate is extracted from brown seaweed species including Macrocystis pyrifera, Laminaria digitata, and Ascophyllum nodosum. When alginic acid is extracted and treated with potassium compounds instead of sodium compounds, it becomes potassium alginate—a white to cream-colored powder with no taste or odor.

In technical terms, potassium alginate is a linear copolymer made up of α-L-guluronic acid (G units) and β-D-mannuronic acid (M units), identical in chemical structure to sodium alginate. The only difference is the mineral base: potassium instead of sodium.

When dissolved in water, potassium alginate creates a thick, viscous solution that mimics the texture and mouthfeel of heavier, fattier foods—allowing manufacturers to create lower-sodium versions of foods without sacrificing creaminess or texture.

Where You’ll Find It

E402 appears in a wide range of processed foods, particularly those targeting reduced-sodium consumers:

• Ice cream and frozen desserts
• Yogurt and dairy products (especially low-fat or low-sodium versions)
• Salad dressings and mayonnaise (particularly low-sodium variants)
• Sauces, gravies, and condiments
• Desserts, puddings, and mousses
• Jams, jellies, and marmalades
• Meat preparations (sausages, pâtés)
• Canned and processed fruits and vegetables
• Beer, soft drinks, and beverages
• Whipped cream and mousses
• Prepared foods and ready-to-eat meals
• Infant and young children’s food supplements and desserts

If you eat processed or prepared foods, especially those marketed as low-sodium, you’ve likely consumed E402 multiple times this week.

Why Do Food Companies Use It?

E402 performs five critical functions:

1. Thickening without sodium: Potassium alginate creates viscosity and body in foods, allowing manufacturers to create rich-tasting, creamy products with lower sodium content. This is especially valuable for consumers watching their salt intake due to hypertension or other health conditions.

2. Stabilization: It prevents oil and water from separating in emulsified products like mayonnaise and salad dressings. Without E402, these products would separate and look unappetizing on store shelves.

3. Gel formation: When calcium or other multivalent ions are added, potassium alginate forms heat-stable gels. This property is used to create jellies, puddings, and structured desserts.

4. Mouthfeel enhancement: It creates a smooth, pleasant texture that mimics the natural feel of fatty foods, improving consumer satisfaction without using excess fat or sodium.

5. Anti-caking properties: In some applications, E402 helps prevent caking and clumping in powdered or dry products.

Without E402, low-sodium processed foods would have inferior textures, thinner consistency, and visible separation of ingredients. For health-conscious consumers reducing sodium intake, E402 is an ideal replacement for sodium-based thickeners.

Is It Safe?

E402 is considered very safe by all major regulatory authorities.

The FDA, EFSA, and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) have all approved potassium alginate for food use. Notably, no specific Acceptable Daily Intake (ADI) limit has been established—meaning regulatory agencies found no safety concern even at very high consumption levels.

JECFA recognizes alginates as safe at consumption levels of up to 50 mg/kg of body weight per day. EFSA’s evaluation concluded “no safety concern and no need to establish an ADI,” reflecting the additive’s excellent safety profile.

Special consideration: For individuals on potassium-restricted diets (common in kidney disease or certain heart conditions), E402 provides an insignificant amount of additional potassium since it’s used at very low concentrations (typically 0.1-1% of total product weight). However, individuals on strict potassium restrictions should consult their healthcare provider if they have concerns.

Potential side effects: Very high intakes could theoretically interfere with iron absorption by binding to iron molecules. However, this is not a practical concern in normal dietary consumption. Some individuals may have mild digestive effects from consuming very large amounts, though this would require excessive intake far exceeding typical food use.

E402 vs E401: What’s the Difference?

E402 and E401 (sodium alginate) are chemically nearly identical—both are alginates extracted from brown seaweed with the same G and M unit composition. The only difference is the mineral base:

E401 (Sodium alginate): Contains sodium as the mineral base. Used in general food products and products where sodium content isn’t a concern.

E402 (Potassium alginate): Contains potassium as the mineral base. Specifically used in reduced-sodium or low-sodium products, marketed to consumers watching their salt intake.

Both are equally safe and effective as thickeners and stabilizers. The choice between them is primarily driven by whether a product is formulated to reduce sodium content.

Natural vs Synthetic Version

E402 is entirely natural—there is no synthetic version.

Potassium alginate is extracted directly from brown seaweed through a physical and chemical process: seaweed is washed with water and acid, then treated with potassium hydroxide or potassium carbonate to convert the insoluble alginic acid to soluble potassium alginate. The solution is then filtered, concentrated, dried, and ground into a powder.

There is no laboratory-created or synthetic alternative—E402 is harvested and refined from nature, making it one of the few food additives that is genuinely 100% natural in origin. The potassium comes from the seaweed itself or is added as a naturally-occurring mineral salt.

Environmental and Health Perspectives

Brown seaweed is a renewable resource that grows rapidly in coastal waters worldwide. Harvesting alginates doesn’t deplete fish stocks or harm marine ecosystems like some fishing practices might. The seaweed regenerates quickly, making alginate production sustainable and environmentally responsible compared to many synthetic food additives.

Beyond food additive use, potassium alginate has applications in medicine, pharmaceuticals, and cosmetics. It’s used in some antacid products, in pharmaceutical formulations, and in cosmetics. Its biodegradability and natural origin make it attractive for sustainable manufacturing.

Natural Alternatives

Want to avoid E402? Food companies sometimes use these alternatives:

• Xanthan gum (E415): A natural polysaccharide produced by fermentation, similar thickening properties
• Locust bean gum (E410): Extracted from carob seeds, natural thickening agent
• Guar gum (E412): From guar bean seeds, similar stabilizing properties
• Gelatin or pectin: Traditional thickeners from animal or plant sources
• Starch or modified starch: From corn, potato, or tapioca—simple carbohydrates
• E401 (Sodium alginate): For products not specifically targeting low-sodium consumers

These alternatives have similar functions but different properties and costs. For low-sodium products, E402 remains the industry standard because of its effectiveness and ability to deliver sodium reduction while maintaining superior texture.

The Bottom Line

E402 (potassium alginate) is a safe, natural food additive derived directly from brown seaweed.

It’s the potassium-based alternative to E401 (sodium alginate), specifically formulated for reduced-sodium or low-sodium food products. It has been extensively studied and approved by all major regulatory agencies worldwide. Unlike many food additives, no safety concerns have been identified, and no ADI limit was deemed necessary. Potassium alginate appears primarily in processed and prepared foods, particularly those marketed to health-conscious consumers reducing sodium intake.

E402 is suitable for vegans and vegetarians, and has no known religious dietary restrictions. For the general population, E402 is one of the safest food additives available, with the same potential health benefits as sodium alginate in terms of cholesterol and blood sugar regulation. If you’re looking to minimize processed foods, reducing intake of products containing E402 would lower overall additive consumption, but the additive itself poses no identified health risk.