Carrageenan

Carrageenan is an umbrella term applied to a number of complex polysaccharides that are extracted from red algae. Their gelation properties differ widely from one variety to another and their behavior is affected by surrounding conditions of temperature, pH, and the presence of ions, especially those from potassium and calcium. Some can curl into helical structures that are able to link loosely together to make up networks. There are three important types of carrageenans, two of which are used as gelling agents: κ-carrageenan, which forms strong, stiff gels; and ι-carrageenan, which forms softer gels that can reassemble themselves after being broken up. The third, λ-carrageenan, is the only one that can be dissolved in cold water; it cannot form gels but is well suited for emulsifying proteins, in particular in dairy products. Gels made from κ- and ι-carrageenan are formed by heating the liquid to the boiling point and then cooling it. Both types are thermoreversible, melting at about 158°F (70°C) and setting again at about 140°F (60°C). They are formed in mixtures containing a carrageenan concentration of 0.8–1 percent in water and 0.3–0.5 percent in milk. In contrast to gels made with ι-carrageenan, those set with κ-carrageenan do not hold up well to being frozen and then thawed. Only 0.02 percent carrageenan is required to slow down the rate at which ice cream melts. In addition, the carrageenan brings out a mouthfeel similar to that of an oil-in-water emulsion, even in a mixture with a low fat content, and it inhibits the formation of ice and sugar crystals in the ice cream so that it does not feel gritty like sand between the teeth. The ability of carrageenan to hold proteins and liquids together has recently found applications in what are called designer fats for meat products, where it helps retain the juices in low-fat meat. Carrageenan also has uses in dairy products and bread, giving structure and preserving moisture. Finally, it has a well-known effect in chocolate milk, holding cocoa particles in suspension so that they do not fall to the bottom. Carrageenan imparts a clean, creamy mouthfeel.