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.