This paper describes the optical characteristics of the Monoolein-PVC membrane in five basic taste solutions such as NaCl (salty), HCl (sour), Saccharose (sweet), Quinine hydrochloride (bitter) and mono-Sodium L-glutamate (umami). The Monoolein-PVC membrane was composed of poly(vinyl chloride) and a synthetic lipid, Monoolein. The optical characteristics of the membrane for the taste solutions could be measured quantitatively as an intensity variation of transmitted light of the membrane, using an optical measurement system with optical fiber. Since the optical intensity of transmitted light increased with different patterns for each taste solution, the membrane is supposed to have an optical selectivity. However, the optical characteristics of the membrane such as detection-threshold and dynamic-range did not agree with human taste characteristic. In order to improve the optical characteristics of the membrane, cholesterol or plasticizer was mixed into the membrane. As a result, the optical characteristics become closer to human characteristics in a few taste solutions. By taking advantage of these optical characteristics, some new usages, optical taste sensors and so on, are expected in the field of ion sensing materials.

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In this paper, electrical and optical characteristics of artificial lipid membrane for basic taste solutions and tea drinks were examined. The possibility of taste sensing on the electrical and optical response patterns of a single membrane was also discussed. As a result, in case of sour and sweet solutions with different concentration, the patterns of taste response were similar in shape. In case of the tea drinks on some commercial goods, the different shapes among the sample solutions were obtained. Furthermore, the strength of sour taste was reflected in the electrical axis of response pattern and the strength of sweet taste was reflected in the optical axis of response pattern. Therefore, it was found that the possibility of taste sensing using electrical and optical response patterns was obtained from a single membrane.

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A living body is receiving quite a lot of information from the external world through sensitive organs for life-supporting. Recently, various physical sensors which measure physical quantity have been developed rapidly. On the other hand, chemical sensors have not developed enough and they are limited to a pH meter, an ion selective electrode and an enzyme sensor. It is difficult to develop sensors for the sense of smell and taste became they have to sense various characters concurrently from chemical substances. We have been studying a possibility of taste sensing using a single artificial lipid membrane. We found that the conductance and transmittance show different characteristics in taste solutions. And we have suggested a way of the taste evaluation by showing features of electrical and optical characteristics as response patterns on a six axis radar-chart. Furthermore, applying the principal component analysis to the response patterns, we have also shown them on the two dimensional coordinate. In this study, we measured the spectrum characteristics of membrane for the purpose of discrimination in the commercial drinks and the condiments. We defined autocorrelation functions in order to evaluate the spectrum characteristics and we utilized Mahalanobis distance as a way of discriminant analysis. We selected two autocorrelation coefficients (hereafter cited as ACC1 and ACC2). One is ACC1 which was put as the value of x-axis and the other is ACC2 which was put as the value of y-axis. We had plots represented from the two ACCs on the two dimensional coordinate. We had known groups obtained by some sample plots. Mahalanobis distances were measured between those plots and the center of gravities of the known groups. As a result, the commercial drinks and the condiments were classified correctly in each category. Therefore, this method was effective to classify category among the commercial drinks and the condiments.

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