Quantitation of κ-, ι- and λ-carrageenans by mid-infrared spectroscopy and PLS regression

Carrageenans are natural products obtained from seaweeds which are used as additives in many industrial fields, mainly in the food industry (labelled as E407). The three most employed ones being the so-called κ-, ι- and λ-carrageenans. So far, their industrial characterisation is based on physical measurements, which exhibit a rather large uncertainty. The aim of this work is to develop a new analytical methodology for the quantitative determination of carrageenans in industrial mixtures employing FTIR and multivariate regression (partial least squares, PLS), avoiding complex sample pre-treatment steps and reducing the turnaround time. The methodology allows to handle liquid (dissolved) carrageenans at room temperature (to prevent degradation), and therefore, their straightforward IR measurement using thin films. The standard prediction errors for the different models selected range from 3.3 to 4.2%, which can be considered as excellent.