TRANSFER OF SPECTRAL DATA BETWEEN FOURIER-TRANSFORM INFRARED SPECTROMETERS FOR USE IN DISCRIMINANT-ANALYSIS OF FRUIT PUREES

The mid-infrared spectra of raspberry and strawberry purees were acqui red on two Fourier-transform spectrometers. A pre-treatment procedure, involving baseline correction and area normalisation, was developed t hat made the spectra from the two spectrometers compatible for use in discriminant analyses. The discriminant analyses were performed by sub jecting the spectra to a principal component (PC) analysis, grouping t hem according to fruit species and then assigning samples to the class with the closest group mean in PC space. Models using the first PC sc ores of the pre-treated spectra from one spectrometer were able to cor rectly assign the fruit species of between 91.1 and 96.4% of the pre-t reated spectra of independent test sets of the other. However, the pro jection of the spectra from each spectrometer into the same PC space s howed differences in the mean positions of equivalent groups along the second and higher PCs. Therefore, the transfer of this data set is on ly wholly reliable using the first PC scores. Tests with the uncorrect ed spectra demonstrated their incompatibility through the complete lac k of overlap of equivalent fruit species groups in PC space.