A compound found in red seaweed, kappa-carrageenan is commonly used as a food additive. Carrageenan is a carbohydrate that can be used to thicken and stabilize foods and as a replacement for fat in some products. When extracted from seaweed, it forms a gel, which can be used to improve the texture of various foods. Kappa-carrageenan is one of three types of carrageenan used as a food additive, and tends to form the firmest gels.
Carrageenan is a linear sulfated polysaccharide, which are sugar molecules connected in a long, straight chain. The sulfated part of the molecule refers to sulfur molecules that are bound to the sugars. The long sugar molecules curl into a helix, forming a gel. The three types of carrageenan — kappa, iota, and lamdba — differ primarily in the number and location of their ester sulfate groups, which affects the temperature at which they dissolve in liquid and how firm a gel they form.
The source of this compound is red seaweed, with different species of seaweed containing different types of carrageenan. Kappaphycus alvarezii contains only the kappa type. Chondrus crispus, Sarcothalia crispata, and Gigartina skottsbergii contain kappa and lambda types. Kappa-carrageenan is most commonly sourced from K. alvarezii and Eucheuma cottonii, also called Kappaphycus cottonii.
Most foods that contain kappa-carrageenan are dairy products. Only a small amount is added in dairy, however, usually less than 0.5 percent. If more is added, then the milk starts to solidify. This additive prevents the fat and protein from separating out into layers, and helps to create a consistent texture. Kappa is typically added to whipped cream to maintain consistent air and lightness.
Removing fat from meat products can produce a dry taste and undesirable texture, so many low-fat meats contain kappa-carrageenan in order to restore the tenderness and juiciness. As much of half of the fat in hot dogs can be replaced using this food additive without adversely effecting the taste. It is also added to poultry products to help prevent the loss of water during the cooking process.
In many instances, kappa-carrageenan can be used as a substitute for gelatin and pectin. In particular, kappa versions are used in calorie free or low-calorie jelly. Combining the three different types of carrageenan creates jellies that do not melt at high temperatures, which is very useful for hot climates. It's also a good substitute for gelatin for people following a vegetarian or vegan diet.
Kappa-carrageenan is also used in a number of non-food products. It is the main ingredient found in air freshener gels, for example. Perfume, water, additives, and potassium salts are all mixed together and molded to fit the freshener container. When the holder is opened, the gel slowly releases the scent into the room.
There are two different methods to remove this carbohydrate from seaweed: by removing everything else from seaweed but the carrageenan and to extract only carrageenan from the seaweed. Originally, carrageenan was extracted into an liquid solution, which was then dried until only the carbohydrate remained. The second method uses base solutions, with a high pH, to dissolve all other compounds but the carbohydrate. The second method is typically much faster and less expensive.