Effect of pH on Depolymerization of κ-Carrageenan by Ultrasound, Ozone and Their Combination

κ-carrageenan is sulphated linear polysaccharides of D-galactose and 3,6-anhydro-D-galactose extracted from certain red seaweeds of the Rhodophyceae class. They have been extensively used in the food and pharmaceutical industry. However, the use of the κ-carrageenan in the biomedical field is inhibited by its easy to form a gel and a high viscosity. Therefore, it is necessary to production of low molecular weight of carrageenan using depolymerization methods. The objective of this research is to study the effect of pH to reduced the molecular weight of κ-carrageenan with ozonation (O3), ultrasonication (US) and the combination of O3 and US (O3-US) methods. The experimental result shows that the O3-US treatment can decrease the molecular weight of κ-carrageenan until 80.77% at pH 7 during 20 minutes of treatment. Depolymerization of κ-carrageenan at pH 3 has the highest percentage compared to pH 7 and pH 10. The percentage depolymerization of κ-carrageenan using O3-US method at pH 3,7 and 10 are 94.22%; 80.77% and 75.85%, respectively.