Degradation of carrageenan by radiation

Abstract

κ-, ι- and λ-Carrageenans were degraded by irradiation with gamma rays in the solid state, gel state or solution with various doses in air at ambient temperature. The molecular weights obtained were in the range of 10.5 × 10 4 to 0.8 × 10 4 of narrow molecular weight distribution. The chemical structural changes of carrageenans were accompanied by appearance of UV absorbance peak at 260 nm and a characteristic FT-IR band at 1728 cm −1. Due to radiation-induced desulfation, carrageenan oligomer has lower sulfate content. From comparison of radiation degradation yield ( G d ), susceptibility to degradation of the three types of carrageenans in aqueous form follows the order of λ > ι > κ which could have been influenced by their conformational state. The oligomer obtained from κ-carrageenan with molecular weight of 1.0 × 10 4 showed a strong growth promotion effect on potato in tissue culture. Degradation of κ-carrageenan solution using vessel-type low energy electron beam accelerator (LEEB) (250 kV, 10 mA) was investigated. LEEB irradiation reduced the molecular weight of carrageenan though the electron beams have a depth penetration range of less than 3 mm in distilled water.