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The evaluation of some red marine algae as a source of carrageenan and of its κ‐ and λ‐components
Author(s) -
Black W. A. P.,
Blakemore W. R.,
Colquhoun J. A.,
Dewar E. T.
Publication year - 1965
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740161001
Subject(s) - carrageenan , stratum spinosum , potassium , chemistry , polysaccharide , hydrolysis , acid hydrolysis , fractionation , botany , food science , chromatography , biology , organic chemistry , genetics , stratum corneum
The red seaweeds, Chondrus crispus, Gigartina stellata, G. radula, G. acicularis, G. pistillata, Eucheuma spinosum , and Polyides rotundus , have been evaluated as a source of carrageenan and of its k‐ and λ‐components. The fractionation of carrageenan from C. crispus with potassium ions does not always give a sharp separation into ‘pure’ k‐ and λ‐components and is dependent on habitat. Seasonal variations in total yield, k/λ ratio, optical rotation and chemical composition were observed. G. stellata and G. radula give poor separations but G. acicularis and G. pistillata give sharp fractionations and the proportion of λ‐polysaccharide in these two species is much higher than that in C. crispus . Approximately 30% of the dry weight of these seaweeds is λ‐carrageenan. Carrageenan from E. spinosum cannot be fractionated with potassium ions. This polysaccharide, which accounts for ˜55% of the dry weight of the seaweed, is structurally related to k‐carrageenan but has a higher sulphate ester content. The extract of P. rotundus is also insensitive to potassium ions but differs from that of E. spinosum in having a negligible content of 3,6‐anhydrogalactose. Different carrageenans have been depolymerised to give products of low viscosity and high sulphate content. This was achieved in the case of k‐carrageenan and carrageenan from E. spinosum by mild treatment with acid. Two methods are described for λ‐carrageenan; the first involves oxidation with periodate, reduction with borohydride, and mild acid hydrolysis. The second method, which is cheaper and more effective, employs hypochlorite as oxidant. A series of degraded products is listed.