What is Carrageenan?
From eggnog and soy milk to infant formulas and toothpaste, carrageenan is found everywhere. The word carrageenan may sound foreign and vaguely exotic, but it’s simply a generic term for a type of sugar extracted from various species of red seaweed. In Modernist cooking, it’s classified as an emulsifier, stabilizer, hydrocolloid (hydrophilic colloid), or gum, all of which function in some way to thicken or clarify ingredients, or to bind moisture. The term carrageenan has been around since at least 1889 and is derived from carrageen, circa 1829, which is a purplish, cartilaginous seaweed colloquially known as “Irish moss,” found off the coasts of North America and Europe. In fact, the seaweed gets its moniker from a small Irish fishing village, Carragheen, where it’s plentiful. Traditionally, the seaweed was boiled in sweetened milk to create a pudding. Simmering the seaweed unlocks the ingredient’s gelling properties. Its use, however, can be traced back even further to at least 400 CE, where it was used as a gelling agent and as an ingredient in homemade cold-and-flu remedies. Industrially, carrageenan is extracted chiefly from the red algae Chondrus crispus (class Rhodophyceae), but it can also be extracted from various species of Gigartina and Eucheuma.
Inherently vegetarian with no nutritional value, seaweed-based thickeners like carrageenan have new, modern applications. Most commonly, carrageenan can adjust the viscosity of dairy products like cheese, or it can serve as an emulsion stabilizer in salad dressings by keeping your oil and vinegar mixed. In more advanced applications, it will glue meat together, allowing for the creation of hot aspics and other seemingly contradictory foundations. Chemically, carrageenan is classified as a polysaccharide, a type of sugar. Its properties are varied and complex, but its basic function is to thicken and stabilize. It does this by forming large yet flexible matrices that curl around and immobilize molecules. Because of its inherent flexibility, carrageenans can form a variety of gels under a wide range of temperatures, but each type of carrageenan only becomes fully hydrated at a characteristic temperature. Some carrageenans can be hydrated without adding heat, while others must be brought to 85°C / 185°F or higher before saturation occurs, and a few have a hydration temperature that depends on the presence of other ions, the most common of which is calcium. Carrageenan actually comes in five varieties, classified by how much sulfate (SO4) it contains and its solubility in potassium chloride. Named after Greek letters, they are ι (iota), κ (kappa), λ (lambda), ε (epsilon), and μ (mu), however, only the forms iota, kappa, and lambda are used in Modernist cooking. All forms contain roughly 20–40% sulphate, which dictates how firmly (and whether) a gel will set, how the gel freezes and thaws, and how syneresis (the separation of water from its gel, also known as weeping) is affected. As the amount of sulfate increases, the strength of a gel decreases.
Recently, there has been some speculation over the safety of carrageenan. Carrageenan has been a focus for many mammal studies because of its potential to cause inflammation, ulceration, colitis, polyps, and colorectal tumors. Although such maladies are reported in animal studies, at the time of writing this connection has not been validated in humans because carrageenan’s molecular size and accompanying bonds prevent it from being digested naturally. To understand why carrageenan does not cause morbidity in humans, it’s important to differentiate between carrageenan and its degraded form, poligeenan. Poligeenan is the digested form of carrageenan and consists of molecular fragments small enough to pass from the digestive tract to the circulatory system. It is poligeenan that causes the many illnesses researchers describe in mammals, but current research has shown that the human digestive tract is limited in its ability to break down carrageenan into poligeenan. The primary pathway of human digestion, the alimentary canal, is, despite its placement, considered to be outside the body; a compound is not considered to be in the body until it moves from the digestive tract to the circulatory system. And, in order for any compound to affect human organs, such as the brain, liver, or heart, it must be small enough to cross the intestinal walls. Carrageenan is too large to do so, but poligeenan’s small size can. Not surprisingly, it has been postulated that carrageenan can be fragmented by natural digestive processes, but, to date, this has yet to be demonstrated in humans. In addition to carrageenan’s large size, its inherent bonds pose another challenge to the human digestive tract. Carrageenan is held together by β-glycosidic bonds, which are ubiquitous in the plant world, but most mammals, including humans, lack the proper enzymes to break them.
Recipes and Sourcing
Because of its utility, carrageenan is an ingredient that we use frequently, appearing in many recipes throughout Modernist Cuisine and Modernist Cuisine at Home. Carrageenan is used to create the creamy texture of our Pistachio Gelato and to stabilize our American Cheese Slices. Although you may not be able to find carrageenan on the shelves of neighborhood grocery stores, it’s easy to source online. If you’re ready to start testing this ingredient, try out our Pistachio Gelato recipe or Raspberry Panna Cotta in Modernist Cuisine at Home.