COMPARATIVE VIBRATIONAL SPECTROSCOPY FOR DETERMINATION OF QUALITY PARAMETERS IN AMIDATED PECTINS AS EVALUATED BY CHEMOMETRICS

The potential of vibrational spectroscopy and chemometrics as a reliab le and fast method for the determination of important gel-forming para meters in amidated pectins has been investigated. For a set of 98 amid ated pectin samples, six complete spectroscopic ensembles were recorde d including NIR, FT-NIR, FT-IR and NIR FT-Raman spectroscopy. For each spectroscopic ensemble, quantitative models based on partial least sq uares regression (PLS) have been developed and compared. Chemometric m odels were constructed by dividing the spectroscopic ensembles up into a calibration set of 73 samples and an independent test set of 25 sam ples to evaluate the predictive ability of the models. The 98 amidated pectin samples span a degree of esterification (%DE) between 20 and 5 5% and a degree of amidation (%DA) between 4 and 24 per cent. From all six spectroscopic ensembles quantitative PLS models were obtained for %DE and %DA with RMSEP (root mean square error of prediction) ranging between 1.5 and 2.1 and between 1.1 and 2.1 for %DE and %DA respectiv ely. In both cases the results are comparable to that of the experimen tal error of the quantitative chemical determination. Finally, differe nt ways of selecting FT-IR spectral elements (variables) to correlate with %DE were compared. The method of principal variables (PV) was fou nd to be superior to methods based on knowledge based selection and th e resulting PV-based model was found to be slightly better than the PL S model using the full spectral information. Copyright (C) 1996 Elsevi er Science Ltd