The stability of carrageenan to depolymerization has been studied both in batch experiments and under physiologically realistic conditions, namely in an artificial stomach. Degradation was characterized from on-line size exclusion chromatography and multiangle laser light scattering data. No hydrolysis of kappa-carrageenan occurs at pH 8 and even under the most drastic conditions (6 h at pH 1.2) the weight-average molecular weight remains >200 kDa only 20% has a molecular weight <100 kDa. This is in marked contrast to the previous findings of Ekstrom. It has been found that carrageenan in helical form (with potassium) is less susceptible to acid hydrolysis.Moreover iota-carrageenan is always more resistant than the kappa form. In simulated gastric juice the degradation of kappa-carrageenan is very limited; only 10% of the carrageenan exposed is reduced to a molecular weight <100 kDa. This is important since toxicological problems, if any, mainly concern poligeenan, a sulphated polysaccharide with molecular weight <100 kDa