Characterising semi-refined iota-carrageenan networks by atomic force microscopy

Abstract

Samples of PNG iota carrageenan have been studied by X-ray diffraction and Atomic Force Microscopy (AFM). Aqueous preparations of PNG iota carrageenan can be fractionated into water soluble and water insoluble components. The water soluble component is largely composed of iota carrageenan containing small amounts of cellulose. AFM studies reveal that this component forms network structures very similar to those obtained for refined iota carrageenan. Some swollen cellulosic networks were observed in the PNG samples. The water insoluble fraction has been shown to be predominately partially crystalline cellulose I. AFM reveals that the cellulose is present as a fibrous network similar to that found for bacterial cellulose or the cellulosic component of plant cell walls. In the PNG samples the lateral ordering of the cellulose microfibrils has been disrupted presumably during the extraction of the PNG carrageenan from the seaweed. The AFM imaging conditions used to study the insoluble component would not permit imaging of any iota carrageenan networks which may be present in this sample.