Effects of extraction parameters on gel properties of carrageenan from Kappaphycus alvarezii (Rhodophyta)

Carrageenan was isolated under different extraction conditions from Kappaphycus alvarezii collected in North Sulawesi, Indonesia. Its gel properties include very strong elasticity even at low concentrations. Molecular weight and rheological properties were obtained by gel permeation chromatography and dynamic viscoelasticity measurements in order to clarify the average molecular weight at various extraction temperatures (50, 70, 90°C) and times (1, 3, 5 h), as well as gel formation ability. The results showed that both the weight-average and the number-average molecular weight decreased with increasing extraction temperature. However, the gelation rate of the carrageenan was found to be constant at around 40°C, whereas the storage modulus, G′, and loss modulus, G″, of the gels differed from each other.