Figure 9: Correlations of sensor output with tannin (a) and Ltheanine (b) included in green tea [lo].
Figure 10 shows the result of PCA applied to response patterns for 41 kinds of commercial mineral water. The right-lower plane contains mineral water with strong hard- ness, i.e., hard water, whereas the left-lower plane is occupied by soft water. The taste of mineral water is quite subtle, and hence it is difficult for humans to discriminate between different brands. However, the taste sensor responded well to the different kinds of mineral water tested. In spite of the low concentrations of taste substances in mineral water, the sensor can discriminate between different brands because of its high sensitivity to ions.
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