Carrageenans or carrageenins are a family of linear sulphated polysaccharides that are extracted from red edible seaweeds. They are widely used in the food industry, for their gelling, thickening, and stabilizing properties. Their main application is in dairy and meat products, due to their strong binding to food proteins. There are three main varieties of carrageenan, which differ in their degree of sulphation. Kappa-carrageenan has one sulphate group per disaccharide. Iota-carrageenan has two sulphates per disaccharide. Lambda carrageenan has three sulphates per disaccharide.

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 Kappaphycus alvarezii.
• Iota forms soft gels in the presence of calcium ions. It is produced mainly from Eucheuma denticulatum.
• Lambda does not gel, and is used to thicken dairy products.

uses in food industry:

• Desserts, ice cream, cream, milkshakes, yogurts, salad dressings, sweetened condensed milks
• Sauces: used to increase viscosity
• Beer: clarifier to remove haze-causing proteins

wikipedia