Carrageenans are commonly classified into different types based on the disaccharide repeating units. These types are abbreviated using Greek letters, with κ-, ι-and λ-carrageenan being the most commercially important carrageenans . The κ-carrageenan repeating unit is composed of a G4S and a DA unit, while the ι-carrageenan repeating unit contains a G4S and a DA2S unit. In contrast, λ-carrageenan is composed of two galactose units (G2S and D2S,6S) . Carrageenans with a D unit instead of a DA unit are commonly referred to as natural precursors. For example, µ-carrageenan (G4S, D6S) is the precursor of κ-carrageenan, while νcarrageenan is the precursor of ι-carrageenan. The sulfated D units of precursor carrageenans can be converted into DA units by the use of enzymes or under alkaline conditions. The latter usually occur during the extraction of carrageenans from red seaweed . Due to the use of different bases, different cations can be associated with the carrageenans. The most abundant cations are potassium, sodium and calcium ions . The cations are an important factor for the aggregation of carrageenan helices during gel formation . Thus, they are important for the functional properties but possibly also for the physiological properties.