Abstract
Freeze dried coffee, filter coffee, tea and cola were
analysed by Curie-point pyrolysis mass spectrometry
(PyMS). Cluster analysis showed, perhaps not
surprisingly, that the discrimination between coffee,
tea and cola was very easy. However, cluster analysis
also indicated that there was a secondary difference
between these beverages which could be attributed to
whether they were caffeine- containing or
decaffeinated. Artificial neural networks (ANNs) could
be trained, with the pyrolysis mass spectra from some
of the freeze dried coffees, to classify correctly the
caffeine status of the unseen spectra of freeze dried
coffee, filter coffee, tea and cola in an independent
test set. However, the information in terms of which
masses in the mass spectrum are important was not
available, which is why ANNs are often perceived as a
'black box' approach to modelling spectra. By contrast,
genetic programs (GPs) could also be used to classify
correctly the caffeine status of the beverages, but
which evolved function trees (or mathematical rules)
enabling the deconvolution of the spectra and which
highlighted that m/z 67, 109 and 165 were the most
significant massed for this classification. Moreover,
the chemical structure of these mass ions could be
assigned to the reproducible pyrolytic degradation
products from caffeine.
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