Pattern recognition procedures for differentiation of Green, Black and Oolong teas according to their metal content from inductively coupled plasma atomic emission spectrometry

Eight metals Zn, Mn, Mg, Cu, Al, Ca, Ba and K selected as chemical descriptors were analysed by inductively coupled plasma atomic emission spectrometry. The metal profile was studied in 48 samples of commercial tea — 26 black, 18 green, and four Oolong teas. Pattern recognition procedures such as display methods (Principal Component analysis and Cluster analysis) and supervised techniques (Linear Discriminant analysis and Artificial Neural Networks trained by back propagation) were applied to attain the differentiation of the three tea classes.