Carrageen, also known as carragheen and Irish moss, is a seaweed that grows and is eaten mainly in the British Isles. Commercially sold carrageen is actually a combination of two species of seaweed, Chondrus crispus (true carrageen) and Mastocarpus stellatus (a mimic of carrageen). Both species are a purple-red color and have numerous short branches that look like moss. They can be found on the rocky shores and tide pools on all the coasts around the Isles. Once picked, the seaweed is commonly bleached in the sun for several days, turning it a pale brown. The term “carrageen” can be traced back to one of two possible origins. One theory is that the term was thought to be derived from the old Irish word “carraigín”, meaning a small rock. The other theory is that carrageen was taken from a landmark in Donegal County in Ireland.
This seaweed is used in a variety of foods and is especially popular in the British Isles. As with other kinds of seaweeds, it is very nutritious and it can be cooked and served as a vegetable. However, carrageen is mainly used as a thickening agent for liquids. The dried seaweed works like gelatin to help set liquids. The seaweed is often used to thicken puddings and custards. The chemical that is responsible for this thickening is called carrageenan. This chemical is commonly extracted from the plant and is widely used commercially as a thickening agent in dairy products, soups, jellies, and toothpaste.
Carrageen can easily be found in Britain and its surrounding areas, but it is much rarer in the United States. The best place to find it is in a health food store or co-op. To use it as a thickener, rinse it well and soak it in warm water until it has become pliable. Then add the softened seaweed to the liquid that will be thickened. Boil the liquid for about ten minutes and then strain and remove the carrageen. One ounce of dried carrageen will thicken about one cup of liquid.
Agar-agar and gelatin can serve as substitutes for the thickening power of carrageen.