ISSN:
1750-3841
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Carrageenan, other sulfated polysaccharides, and carboxylic acid polysaccharides react with hexol nitrate, hexamine cobaltic chloride, and tris-(ethylenediamine) -cobalt III chloride in aqueous solution to give precipitates which exhibit differential solubilities in solutions of simple salts. The turbidity (optical density) produced when the hydrocolloids are mixed with these cobalt complexes is proportional to the amount of hydrocolloid present. Salts inhibit the reaction, and, generally, the order of inhibition is: monovalent cations 〈 divalent cations 〈 trivalent cations.The temperature and pH of the reaction medium greatly influence the final turbidity developed. Generally, the complexes formed through the reaction of the sulfated polysaccharides and the cobalt complexes are less readily dissolved by solutions of simple salts than those formed by the carboxylic polysaccharides and the cobalt complexes. Neutral polysaccharides are not precipitated by the cobalt complexes, hence three component systems containing a sulfated, a carboxylic, and a neutral polysaccharide can be resolved and the individual components determined quantitatively. Good resolution was obtained with a mixture such as carrageenan (sulfated) plus algin (carboxylic) plus locust bean gum (neutral).Quantitative assay of those polysaccharides which form precipitates (turbidity) with the complexes can be done either by measuring the turbidity developed or by determining spectrophotometrically the amount of cobalt complex cation bound. These colored complexes have sharp absorption maxima: hexol nitrate, max = 490 mμ; hexaminecobalt chloride, max = 475 mμ; and tris-(ethylenediamine)-cobalt III chloride, max = 470 mμ.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2621.1966.tb00507.x
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