Used for a long time in Ireland, where it is also known as carrageen moss, the inhabitants of this country gave carrageenan its name. As it creates a creamy texture, this dried seaweed was originally boiled with milk to make pudding or thicken infant formula.
Like agar-agar, carrageenan is a hydrocolloid obtained from the cell walls of red algae. As there is a large variety of algae used for extracting the product, their chemical characteristics differ greatly and allow a multitude of uses depending on their origins and composition. Three types of carrageenan stand out depending on the predominance of sugar in their structure: kappa, iota and lambda, which come respectively from Kappachycus alvarezii, Eucheuma denticulatum and Chondrus crispus. Other seaweed is also harvested, including Furcellaria, Gigartina and Iridaea.
The main goal of processing is to isolate the hydrocolloid locked inside the algae. To do this, chemical agents (salts, alcohols, alkalies) and mechanical means, such as filtration, concentration, drying and grinding, are applied to the plant. The salts chosen to extract carrageenan greatly depend on the desired final product and desired gelling properties, since they cause molecular rearrangement. Production of carrageenan requires great precision, in-depth knowledge of its gelling and thickening properties, and standardized procedures in order to create identical mixtures every time and thereby ensure production consistency.
Due to its composition, KAPPA carrageenan forms a brittle, firm gel, which is potentiated and stabilized by the presence of potassium. Many layers of kappa molecules join together forming double helices that produce this particular texture. The final product is greatly affected by salts, sugar or proteins, such as those present in milk. Interactions between positive and negative charges of the additive and solution create a network similar to the meshes of a net, which keep all of the particles in suspension, preventing their aggregation and the collapse of the structure.
IOTA carrageenan has greater affinity with calcium, although it is not necessary in order for it to congeal. Calcium, like potassium with kappa carrageenan, lodges between double helices to stabilize the gel. Iota carrageenan usually produces an elastic gel that does not degrade if it is frozen and thawed. It also forms a stronger gel in the presence of starch.
The third type of carrageenan, LAMBDA, significantly differs from the other two. It does not gel, with or without the addition of ions, but is used to thicken dairy products. It is used less often, but is sometimes combined with kappa to change the texture of certain products.
Finally, it is important to note that acidic foods destroy polysaccharide chains and prevent the product from congealing. It is therefore essential to add this type of ingredient at the very last moment.