To study the structural and functional heterogeneity of commercial carrageenans, 16 samples were purchased from different suppliers. The carrageenans were classified into different types (see section 2.1) and intended for use as laboratory chemicals or food additives. All samples were analyzed for their structural composition by using NMR spectroscopy, HPSEC-RI/MALLS, ICP-OES, and ion chromatography. Based on the results, selected carrageenans were subjected to further analysis by partial enzymatic hydrolysis and rheology.