NIR spectra in relation to viscoelastic properties of mixtures of Na-κ-Carrageenan, locust bean gum and casein

Near-infrared spectral data were correlated with the viscoelastic property storage modulus, G', for mixtures of five biopolymers using multivariate analysis. Gels containing Na-kappa-carrageenan (0.5-1.0%) mixed with locust bean gums with two different mannose to galactose ratios, alpha-casein and/or kappa-casein (0-0.5%, polymer concentration) in 0.25 M NaCl were studied. Forty-two experiments based on a multivariate, central composite circumscribed design (CCC) were performed. Partial least square (PLS) regression was used to find a model relation between NIR transmittance spectra, recorded at 15 degrees C in the wavelength interval 40-2500 nm, and the G' for the biopolymer gels at 15 degrees C. Depending on sample composition, the G' varies between 0 and 3500 Pa. Cross-validation using a designed data set led to a model based on 11 principal components with a correlation coefficient of 0.85 and a root mean square error of prediction of 540 Pa. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.