Radiolysis studies of aqueous κ-carrageenan

The effects on N2O and N2 gas on the radiation degradation yield of aqueous kappa (κ-) carrageenan were investigated. The Gd of solution saturated with N2O solution was expectedly much higher than in air (1.7 and 1.2 × 10−7 mol J−1). On the other hand, a lower Gd of 1.1 × 10−7 mol J−1 was obtained from κ-carrageenan solution saturated with N2.The rate constant of reaction of OH radicals with sonicated and irradiated κ-carrageenan were determined using e-beam pulse radiolysis. The rate constant of OH interaction with sonicated κ-carrageenan decreased with decreasing molecular weight. On the other hand, the OH interaction with irradiated κ-carrageenan decreased but did not vary significantly with decreasing molecular weight. Metal ion (Na+) induced conformational transition into helical form decreased the rate constant of OH reaction with κ-carrageenan. Likewise, the Gd in aqueous form was affected by the conformational state of κ-carrageenan. The helical conformation gave a lower Gd (7 × 10−8 mol J−1) than the coiled conformation (Gd = 1.2 × 10−7 mol J−1).