Carrageenan is a common food additive that is extracted from a red seaweed (Chondrus crispus) which is popularly known as Irish moss. It is a mixture of indigestible carbohydrates, polysaccharides composed mainly of galactose and has been used as thickening agent to improve the texture of Jelly, whipped cream, ice cream, yogurt, chocolate milk and other processed foods.
Based on its gelling ability, carrageenan is divided into three commercial classes:
Kappa forms strong, rigid gels in the presence of potassium ions; it reacts with dairy proteins. It is sourced mainly from Kappaphycus alvarezii.
Iota forms soft gels in the presence of calcium ions. It is produced mainly from Eucheuma denticulatum.
Lambda does not form gel and is used to thicken dairy products. The most common source is Gigartina from South America.