The regular backbone structure of The basic structure of carrageenan is disrupted by a more or less
ordered distribution of sulphate hemi ester groups. Carrageenan can also contain some methoxy and
pyruvate groups.
The original classification of carrageenan was determined by the fractionation of the polysaccharide
with potassium chloride.The fraction that was soluble in 0.25M KCl was called lambda carrageenan
and the fraction that was insoluble was called kappa carrageenan. Rees and his co-workers later
altered this so that kappa and lambda carrageenan referred to idealised specific disaccharides.