APPLICATION OF CHEMOMETRICS TO THE H-1-NMR SPECTRA OF APPLE JUICES - DISCRIMINATION BETWEEN APPLE VARIETIES

Discrimination between apple juices produced from different varieties (Spartan, Bramley, Russet) has been achieved by applying principal com ponents analysis (PCA) and linear discriminant analysis to H-1 NMR spe ctra of the juices. The use of covariance and correlation matrix PCA m ethods was investigated and different regions of the spectrum were ana lysed in view of the large range of signal intensities. All the method s gave a high success rate of classification, with at least 24 out of 26 samples being correctly assigned when five principal components wer e used. Under optimum conditions a 100% success rate was achieved. Exa mination of the principal component loadings showed that the levels of malic acid and sucrose were two important chemical variables, but var iations in the composition of the minor constituents were also found t o make a significant contribution to the discrimination. (C) 1998 Else vier Science Ltd. All rights reserved.