The term “carrageenan” is used to name a class of commercially important sulphated galactan polysaccharides extracted from red seaweed. The three principal types of industrial importance are kappa, iota and lambda carrageenan, extensively used in the food, pharmaceutical and cosmetic industry as viscosity builders, gelling agents and stabilisers. Their commercial forms are rarely pure and normally contain varying amounts of the other carrageenan types. Traditional methods for the structural analysis of carrageenans require hydrolysis and derivation procedures followed by chromatographic analysis of the formed derivatives. These assays are time-consuming and do not adequately quantify the different components in blend samples. Because the influence of carrageenans blend composition on their properties and functionality different analytical methods have been applied, but still there is a lack of adequate analytical techniques, suitable for industrial analytical routine operation, to quantify the relative concentration of the different carrageenans in mixtures.
The present work is aimed to summarise recent developments on carrageenan analysis by applying 1H-NMR and FT-IR spectroscopy. A new analytical methodology for the quantitative determination of carrageenans in industrial mixtures employing 1H- NMR and FT-IR spectroscopy combined with partial least squares multivariate regression (PLS) is described. This method allows to predict the relative concentration of the different carrageenans present in blends in a short and accurate manner by a rapid IR analysis.
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