Multi-way analysis for investigation of industrial pectin using an analytical liquid dilution system

12 pages, 7 figures, 2 tables.-- Printed version published Dec 2006.-- Issue title: "Selected papers presented at the 9th Scandinavian Symposium on Chemometrics (SSC9, Reykjavik, Iceland, Aug 21–25, 2005)".Measurements from an analytical liquid dilution system are used to quantify the intra-molecular distribution of ester groups on the pectin carbohydrate backbone. Thirty-one pectins have been produced from remethylated pectin by enzymatically deesterifying them in steps to give different known ester distributions. The amount of deesterification is measured in each step by titration to provide the reference values. The system works by injecting a solution of pectin into a carrier stream containing a fixed concentration of dye. The dye binds site-specifically to the poly-α-(1 → 4)-D-galacturonic acids constituting the non-esterified parts of the pectin carbohydrate backbone. The carrier stream is led to a Continuously Stirred Tank Reactor (CSTR). The pectin is slowly diluted while UV–VIS spectra are recorded at the reactor outlet providing a landscape of wavelength-by-time for every sample. All pectins are measured this way in triplicate runs.In an article preceding this, the acquired landscapes have been analysed qualitatively using Multivariate Curve Resolution (MCR) and PARAFAC2, both Alternating Least Squares (ALS) regression algorithms. It is concluded that the landscapes can be described by common spectral profiles for all pectins and individual concentration/time profiles for each sample run.In this article, calibration to the reference values are done by multi-way Partial Least Squares (PLS) regression to correlate the acquired landscapes as independent variables directly to the reference values as dependent variables. Also, calibration is done by unfolding the landscapes for each sample run to a vector and use conventional PLS. The concentration/time profiles previously identified by MCR-ALS or PARAFAC2 are unfolded and used as independent variables in PLS rather than the whole landscape. Finally, the spectral information can be reduced even further by summing up or integrating the mentioned individual concentration profiles to just one number per profile identified by MCR-ALS or PARAFAC2 in the sample run, or using the identified score values for each profile from the PARAFAC2 model as new independent variables.The most successful calibration models based on a calibration set built from one of the triplicates can predict the induced degree of deesterification to an error level of less than 3% in absolute values–corresponding to a 6% relative error to the calibration full range–when tested onto a set consisting of the two remaining sample runs from the full set. The best calibration models are based either on unfolded landscapes or unfolded concentration profiles resolved by MCR-ALS.The authors would like to gratefully acknowledge the grant made available by the Ministry of Science, Technology and Innovation to Christian B. Zachariassen, to partly cover the expenses in connection with participation in the Industrial PhD project, which is a joint effort between CP Kelco and the Quality and Technology Group, The Royal Veterinary and Agricultural University of Denmark.Peer reviewe

Comparison of PARAFAC2 and MCR-ALS for resolution of an analytical liquid dilution system

13 pages, 3 tables, 9 figures.-- Printed version published Jul 7, 2006.An analytical liquid dilution system is proposed to collect information on the intramolecular distribution of ester groups on the pectin carbohydrate backbone by injecting a solution of pectin into a carrier stream containing a fixed concentration of dye. The dye binds site-specifically to the poly-α-(1→4)-D-galacturonic acid units which are not esterified. The carrier stream is led to a Continuously Stirred Tank Reactor (CSTR). The pectin is slowly diluted while UV–VIS spectra are continuously recorded at the reactor outlet, providing a wavelength-by-time matrix for every sample. Thirty-one pectins, enzymatically deesterified to give different ester distributions, are measured using remethylated lemon pectin as starting material. The combined sample matrices are analysed using multi-sample Multivariate Curve Resolution (MCR) and PARAFAC2, both Alternating Least Squares (ALS) regression algorithms. Both algorithms successfully describe the data giving a lack of fit between 2.0% and 8.3%, depending on the number of components extracted and the choice of constraints applied. The paper discusses how and on which terms the two algorithms can be compared. Interpretable information about the deesterification pattern of the pectin-related species and the extent of deesterification is obtained from the resolved dilution concentration profiles. The most detailed chemical description of the pectin-dye species is obtained with an unconstrained MCR-ALS five-component model.The authors would like to gratefully acknowledge the grant made available by the Ministry of Science, Technology and Innovation to Christian B. Zachariassen, to partly cover the expenses in connection with participation in the Industrial Ph.D. project, which is a joint effort between CP Kelco and the Quality and Technology Group, The Royal Veterinary and Agricultural University of Denmark.Peer reviewe