To convert ν-units into ι-units, 250 mg of carrageenan were mixed with 125 mL of a 1 M sodium hydroxide solution. The sample was treated in a water bath at a temperature of 80 °C for 35 minutes . The solution was then cooled to room temperature in an ice bath and neutralized with 1 M hydrochloric acid. After neutralization, the volume of the solution was reduced to 100 ml by rotary evaporation. To remove excess salt, the sample solution was dialyzed for 20 h against Milli-Q water (dialysis solution was changed twice). Finally, the sample was freezedried. By using sodium hydroxide for the structural modification, the sodium form of the modified carrageenan was obtained. In order to prepare other monocationic forms of the modified carrageenan, the sample was subjected to the cation exchange process described above.