Carrageenans are a family of linear sulfated polysaccharides that are extracted from red seaweeds.
Carrageenans have the ability to form a variety of different gels at room temperature. They are widely used in the food and other industries as thickening and stabilizing agents. A particular advantage is that they are pseudoplastic—they thin under shear stress and recover their viscosity once the stress is removed. This means that they are easy to pump but stiffen again afterwards.
There are three main commercial classes of carrageenan:
Kappa forms strong, rigid gels in the presence of potassium ions; it reacts with dairy proteins. It is sourced mainly from Eucheuma cottonii. It is often used in breading and batter due to its gelling nature.
Iota forms soft gels in the presence of calcium ions. It is produced mainly from Eucheuma spinosum. It is often is used in fruit applications to develop a heat-reversible and flexible gel.
Lambda does not gel, and is used to thicken dairy products. The most common source is Gigartina from South America. It also assists in binding, retaining moisture and in contributing to viscosity in sweet doughs.