What is Sodium Alginate (E401)? Properties, Uses, Safe and Side Effects

What is Sodium Alginate (E401)? Properties, Uses, Safe and Side Effects


Table of Contents

Sodium alginate is a food additive used primarily as a thickening, stabilizing, and gelling agent in foods. It improves texture, increases viscosity and stability, and prevents syneresis. It has many other uses as well, some of them listed below. Sodium alginate is made from aqueous extract of seaweed (brown seaweed), and sodium salt is extracted from this alginic acid. It gets the name alginate from its alginic acid content.

What is sodium alginate?


Sodium alginate is a natural product that is extracted from brown seaweeds. It is used as an emulsifier, thickener, and stabilizer in foods. It’s also used in some pharmaceuticals and cosmetics.

Sodium alginate is usually supplied as a fine white powder, but it can be made into a gel by adding calcium ions. Sodium alginate has a wide range of properties including high viscosity, good foam stability, and gel strength. It’s often used in making toothpaste gels and ice cream because of its ability to produce a strong gel in low concentrations.

Sodium alginate can be used as an emulsifier in food products such as cheese spreads or salad dressings because it helps disperse oil droplets evenly throughout the liquid phase. It’s also frequently used as a stabilizer for foams and emulsions that are prone to break down easily (such as mayonnaise).

What is sodium alginate used for?


Sodium alginate is a natural extract from seaweed that has been used for centuries in medicine and food processing. In medicine, sodium alginate is used to treat burns; in food processing, it’s most commonly used as an emulsifier or thickener in foods such as ice cream, cheese and salad dressing.

In addition to its use as an emulsifier or thickener in foods, sodium alginate can also be added to certain beverages such as beer to help stabilize foam formation. It does this by absorbing carbon dioxide gas from the liquid during fermentation, which allows brewers to control the amount of foam on their product.

How is Sodium Alginate produce?


Natural calcium, magnesium, and sodium salts of alginic acid are present in brown seaweed cell walls. Macrocystis, Ascophyllum, Durvillaea, Ecklonia, Laminaria, Lessonia, and Sargassum are the most commonly used species for the production of alginic acid and its salts.

Alginic acid and sodium carbonate react to produce sodium alginate. In brief, the manufacturing process is:

  1. Seaweed is washed with water and acid to remove water-soluble substances, such as sodium chloride, colors and soluble proteins.
  2. Adding sodium carbonate to insoluble ingredients (alginic acid and calcium alginate) converts them to soluble sodium alginate, then filtration removes the cellulose (insoluble).
  3. The sodium alginate is converted to alginic acid by adding acid or calcium chloride to form calcium alginate first and then washing with acid.
  4. After neutralization with sodium carbonate, the product is dried, granulated, or sieved.


Other names
  • Algin gum
  • Alginic acid, sodium salt
CAS number 9005-38-3
Chemical formula (C6H7NaO6)n
Molecular weight 10 000 -600 000 (typical average)





Filamentous or granular, white to yellowish brown, with little odor or taste.




Polysaccharide sodium alginate is mainly composed of *-L-guluronic acid (G unit) and *-D-mannuronic acid (M unit) connected by glycosidic bonds (1*4).

Depending on the seaweed species and season, the M/G ratio will influence viscosity, gelling capability, and gel strength.


Calcium and magnesium alginate are insoluble in ethanol while calcium and magnesium alginate are soluble in water.


In general, viscosity depends on:

  • Polymerization degree
  • A sodium alginate polymer’s molecular weight
  • The temperature
  • The concentration
  • Metal cations with polyvalent properties

As a thickener, it can have a viscosity of 4 to 1000 mPa*s in its food grade (1% solution).


In food applications, the pH ranges from 4.0 to 10.0.


Acids or multivalent cations, such as calcium, copper, and lead ions, form heat-stable gels.

For example, jelly is produced by reacting calcium salts with sodium alginate solutions to form a gel containing calcium ions that crosslink polymers.

As shown in the following image, alginate gel is more heat stable than gelatin, carrageenan, and agar gels.


Combining sodium alginate and pectin results in a firmer gel. In contrast to sodium alginate gels (with calcium ions), these gels are thermo-reversible.

What is sodium alginate made of?

Sodium alginate is a white powder made from seaweed. It’s used to thicken the texture of liquids and to bind ingredients together.

Sodium alginate is a carbohydrate derived from brown algae in the genus Laminaria or kelp. Algae grow in ocean water, where they’re exposed to calcium, magnesium and sodium ions. These elements combine with proteins in seaweeds to form a gel that helps them trap and store nutrients in their cells.

Alginate isn’t found naturally in foods, except for some types of seaweed and algae. But it’s added to many processed foods as a thickening agent or gelling agent for sauces, dressings, and other products like ice cream.

It’s also used as a stabilizer in beer foam. This helps prevent beer from oxidizing too quickly when it comes out of the tap at bars or restaurants so it lasts longer before going flat.

How does sodium alginate work?

Sodium alginate works by forming gels when mixed with water. The gel formation is triggered by ions such as calcium, magnesium and sodium ions in the water solution. When these ions are present in large concentrations, they displace water molecules from the sodium alginate molecules, causing them to swell up and form a gel matrix.

The gel strength of sodium alginates depends on their concentration in solution (the higher the concentration, the stronger the gel). The ability of sodium alginate to form gels also depends on its molecular weight: high-molecular-weight sodium alginates form stronger gels than low-molecular-weight ones.

What are the application of sodium alginate?

Because of its properties of thickening, gelling, and stabilizing, sodium alginate is widely used in food, especially dairy-based products (e.g. ice cream, yogurt, pudding, cheese sauce, and desserts).

Applications include:

Ice cream

Besides providing a smooth and soft mouthfeel, it stabilizes the bubbles in frozen ice cream and prevents sugar crystals from forming.


As calcium ions can make sodium alginate gel, sodium alginate and calcium chloride or calcium lactate can be used to shape liquids into squishy beads or worms. As a result, food flavor and color can be encapsulated inside the spheres.


With sodium alginate (combined with calcium chloride), meat products can retain more water, increase their elasticity, and remain fresh for longer.

A gel of calcium alginate is formed when sodium alginate and calcium ions are mixed together.


Dietary supplements can use it to regulate appetite and energy intake. In fortified foods and supplements, sodium alginate, konjac glucomannan, and xanthan gum are blended to make alginate-konjac-xanthan polysaccharide complex (PGX).


In addition to its use as a binder, it can also be used in pet products and for livestock that is not a food producer.


As an excipient in pharmaceutical products, it can reduce the reflux of gastric contents.

Is sodium alginate safe to eat for body?

This product has been approved as safe by the FDA, the European Food Safety Authority (EFSA), and Food Additives Expert Committee of the FAO/WHO.


As a thickener, stabilizer, texturizer, and firming agent, sodium alginate is generally considered safe (GRAS):

  • Relishes and condiments
  • Frostings and confections
  • Puddings and gelatins
  • Candy that is hard
  • Fruit juices and processed fruits
  • Categories of other foods


As an authorised food additive, sodium alginate (E401) is categorized as “other additives than colours and sweeteners” in Commission Regulation (EU) No 231/2012.

Safety re-evaluation in 2017

According to EFSA, alginic acid and its salts of sodium, potassium, ammonium, and calcium are safe as food additives:

  • In food additives, there is no safety concern or need to establish safety.
  • Children and infants should be given doses below therapeutic levels.
  • It was not adequately assessed whether it was safe when used in “dietary foods for special medical purposes and special formula for infants” and in “dietary foods for babies and young people for special medical purposes”.

Approved uses

A number of alginate chemicals are listed separately in “Group I” with the maximum level of use being “quantum satis”. Among them are alginic acid (E400), potassium alginate (E402), calcium alginate (E404) and ammonium alginate (E403). It may be present in the following foods:

  • Pasteurised cream without flavor
  • Preparations of meat
  • Puddings and desserts
  • Marmalades, jams, and jellies

UK Food Standards Agency

The following are classified as “Emulsifiers, stabilizers, agar, the thickeners, and gelling agents”

Food Standards Australia New Zealand

Australian and New Zealand have approved code number 401 for it.


Ingredient function class: food additives, emulsifier, stabilizer, thickener.

In 1992, the ADI was set as “not specific.”.

How much sodium citrate to use?

The amount of sodium citrate that you should use depends on the pH of your product. The pH scale ranges from 0 to 14, with 7 being neutral. The lower the number, the more acidic a solution is. If a liquid has a pH below 7, it is considered acidic. If a liquid has a pH above 7, it is considered basic or alkaline.

For example, lemon juice has a pH of approximately 2.3 while baking soda (sodium bicarbonate) has a pH of 9.7 — making it very basic (alkaline).

How much sodium citrate for cheese sauce?

The amount of sodium citrate needed depends on the pH of the cheese and the thickness of your sauce.

If your cheese is at a pH less than 5.4, you will need to add sodium citrate to lower the pH. NCHFP recommends adding 0.5 oz per pound of cheese for a 25 degree reduction in pH.

If your cheese is at a pH greater than 5.6, you can add sodium citrate to raise it, but this will be more difficult because the higher the pH, the greater effect that sodium citrate has on raising it. NCHFP recommends adding 0.5 oz per pound of cheese for a 25 degree increase in pH while maintaining good flavor and texture characteristics.

If making a thick sauce, you’ll want it to be able to hold its shape when ladled out onto macaroni or spaghetti noodles.;

How to use sodium alginate for reflux?

Sodium alginate can be used in different ways depending on the severity of your condition. If you are just looking for some relief from heartburn symptoms (acid reflux), then you can use it as an antacid by dissolving one teaspoon of sodium alginate powder in a glass of water and drinking it after meals.

However, if you have severe heartburn symptoms which do not get better with conventional medicines or home remedies for acid reflux, then you may consider using sodium alginate as an antacid too.

For this purpose, dissolve one teaspoon of sodium alginate powder in one cup of water and drink it after meals twice daily or three times daily if needed. You should continue taking this remedy until your symptoms subside completely.

What is sodium alginate side effects?

Sodium alginate can be used as an emulsifier, stabilizer or thickener in food products. It is also used in the production of plastics, paper coatings and papermaking.

Side effects of sodium alginate may include:

Allergic reactions. Some people who are allergic to latex may also be allergic to sodium alginate. A skin rash or hives may occur after contact with sodium alginate.

High blood pressure. Sodium alginate can cause a sudden increase in blood pressure after surgery due to its ability to slow absorption of fluids from the intestines into the bloodstream. This effect may last for several days after surgery.

Gastrointestinal problems like diarrhea, nausea and vomiting have been reported as side effects of sodium alginate use in some cases.

Diarrhea. Diarrhea is common after surgery when patients take nonsteroidal anti-inflammatory drugs (NSAIDs) or other medications that affect the digestive system.

Where to buy sodium alginate?

Sodium alginate is a food additive and it can be purchased online at Amazon or Alginic Acid Supplier. The price for a 500g bag is about $8.

Sodium alginate is also available in larger quantities at food grade quality from Grade Chemical suppliers.

Alginate powder can be used to thicken salad dressings, mayonnaise and other sauces, as well as being used as an emulsifier in ice cream and sherbet.

Frequently asked questions

How to use sodium alginate?

Sodium alginate is a powder made from seaweed. It’s often used in food products and cosmetics to create thick, gel-like substances. To use sodium alginate, you’ll need to mix it with water and agar agar.

The ratio of sodium alginate to water should be 1:4, with the final mixture being about 2% to 3% sodium alginate. The amount of agar agar needed will depend on how much you’re making, but it should be between 0.2% and 0.3%.

Once your base has been mixed with these ingredients, add your food coloring or other ingredients if desired. Then pour into molds or shapes (such as ice trays or muffin tins). After this, place your mold in the fridge for at least an hour before serving!

Is sodium alginate safe?

Sodium alginate is a safe food additive that has been used for thousands of years. It is used to thicken and stabilize foods such as yogurt and ice cream, as well as to prevent separation in products like margarine. Sodium alginate is a carbohydrate found in brown algae, seaweed and other marine plants.

How much sodium alginate to use?

The amount of sodium alginate you need to use depends on the weight of your food. To make a thick gel, you will need to use 1 gram of sodium alginate per 100 grams (3.5 ounces) of food. To make a liquid gel, you will need to use 0.5 grams of sodium alginate per 100 grams (3.5 ounces) of food.

Is sodium alginate natural?

Yes,  Sodium alginate is a natural substance that occurs in seaweed. It can also be synthesized artificially, but the synthetic version is identical to the natural one.

Is sodium alginate vegan?

Yes, Sodium alginate is a seaweed extract that’s used in vegan cooking. It’s made from the cell walls of brown algae, so it does contain some animal products. However, it can be used in vegan recipes because it’s often extracted from wild-harvested plants.

Is sodium alginate a hydrocolloid?

Yes, sodium alginate is a hydrocolloid.

Hydrocolloids are compounds that can form gels in water. They are used in many food and beverage products as thickening agents or stabilizers. Sodium alginate is one type of hydrocolloid. It is a carbohydrate polymer made from the cell walls of brown seaweed that helps to thicken foods, especially those that have dairy products or sauces in them.

What’re the sodium alginate benefits?

Sodium alginate is an ingredient that’s often used in cosmetics and beauty products. It’s a natural polysaccharide that comes from brown algae and has a number of benefits.

1. Alginate can help to soften skin.

2. It can even out skin tone and reduce the appearance of wrinkles.

3. Sodium alginate is used as a thickener in lotions and creams, which helps them spread more easily on the skin

Final words:

With that said, sodium alginate is a natural product and safe to consume at levels that are currently used in the food industry. In fact, sodium alginate is considered to be a safe additive by The European Scientific Commission on Food Safety. Sodium alginate is most commonly used as a thickening agent in a variety of different products such as ice cream, gelatins, puddings and marshmallows. As long as these products are consumed in moderation and with other sources of nutrition then there shouldn’t be any cause for concern.

if you have any questions about this additive, feel free to contact us in the comments.

Sophie Feng

Sophie Feng

Sophie Feng is the author of gradechemical.com, she is the co-founder of the grade chemical network. She has been in grade chemical company since 2017, with a working knowledge of food chemical .

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