Sodium Alginate

Brief overview

Sodium alginate is a naturally occurring polysaccharide found in brown seaweed weeds. It is a sodium alginate salt of formula (C₆H₇O₆Na). Sodium alginate is soluble in hot and cold water and can be cured and bonded.

Manufacturing Process

1.  Alginic acid method

Acid is added to the extract, and alginic acid is formed as gelatinous pieces. This is removed by floatation facilitated by carbon dioxide, which is obtained when excess carbonate is added initially. The remaining extract contains tiny alginic acid, 1 - 2%, which is concentrated to 7 - 8 % by centrifuging. To this alcohol, the solution is added, and then solid sodium carbonate is added till the required pH is reached. The sodium alginate is extruded in the form of pellets, oven dried and milled.

2. Calcium Alginate method

This method adds calcium chloride to the extract to obtain solid calcium alginate as fibres. The fibrous material can be removed by sieving, and excess calcium is removed using water. It is stirred with dilute acid to give alginic acid, and this is screw pressed to form a paste. To this solid, sodium carbonate is added till the required pH is reached. The sodium alginate is extruded in the form of pellets, oven dried and milled.

Food Industry

Sodium alginate is used in the food industry to increase viscosity and as an emulsifier. Sodium alginate is used as a stabilizer for ice cream, yoghurt, butter and cheese. Sodium alginate can also be used as a thickener and emulsifier for salads, puddings, jams, tomato juice and canned products. It is used as a hydrating agent for noodles, bread, and frozen products. Sodium alginate is widely used to produce gelatinous products of sauce.

Pharmaceutical Industry

Alginate swells in water, and the pharmaceutical industry uses this property as a disintegrant. It is used in liquid medicines to increase viscosity and solid suspension. It is also used to fix cells and enzymes.

Other Industry

Sodium alginate has the ability to thicken in water, making it suitable for textile printing. It is used for the surface sizing of paper. Its oil resistance to paper is also better. Alginates are widely used in the dental industry as impression materials. It is a good chelating agent for extracting radioactive substances from the body.