Carrageenan is a hydrocolloid extracted from some red seaweeds belonging to the Gigartina, Hypnea, Eucheuma, Chondrus and Iridaea species. It is used in a wide variety of applications in the food industry as a thickening, gelling, stabilizing and suspending agent in water and milk systems.
Carrageenan is a multifunctional ingredient and it behaves differently in water and in milk systems. In water it shows typical hydrocolloid properties of thickening and gelling, while in milk systems it also has the property of reacting with proteins to furnish additional stabilizing abilities.
Carrageenan has a unique ability to form a wide variety of gel textures at room temperature: rigid or elastic, clear or turbid, tough or tender, heat stable or thermally reversible, low or high melting/gelling temperatures. It may also be used as a suspending, gelling, emulsifying, stabilizing and water retaining agent in other industrial applications.
Carrageenan can be classified according to its structure and chemical properties or according to its production process:
1. STRUCTURE AND CHEMICAL PROPERTIES
KAPPA - rigid and brittle gel, thermo-reversible, high gel strength, showing syneresis.
IOTA - elastic gel, thermo-reversible, no syneresis, thixotropic.

2. PRODUCTION PROCESS
SEMI-REFINED - opaque gel containing high cellulose and fiber levels, low degree of purity.
REFINED - clear, transparent gel, with a high degree of purity.