Fig. 7 shows the relative and CPA values obtained from an acidic bitterness sensor, i.e., sensor electrode for acidic bitterness (Table 1) for samples with basic tastes. The relative value for the acidic bitter substance is –100 mV, whereas those for the salty and umami substances are approximately –40 mV. In contrast, the CPA value is –67 mV for the acidic bitter substance but is nearly zero for other taste substances. Namely, the CPA value of the acidic bitterness sensor is highly selective to acidic bitter substances. Fig. 8 shows the measurement results obtained from a basic bitterness sensor, i.e., sensor electrode for basic bitterness. Four bitter substances and other taste substances [29] were tested. From the CPA values, the basic bitterness sensor responds to all bitter substances but does not respond to other taste substances. These results support the fact that the basic bitterness sensor has global selectivity. In addition, the CPA value highly correlates with the results of sensory evaluation, as shown in Fig. 8. As mentioned above, the basic bitterness sensor conforms to the concept of the taste sensing system described in Section 3.