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Effective R&D and strict quality control of a broad range of foods, beverages, and pharmaceutical products require objective taste evaluation. Advanced taste sensors using artificial-lipid membranes have been developed based on concepts of global selectivity and high correlation with human sensory score. These sensors respond similarly to similar basic tastes, which they quantify with high correlations to sensory score. Using these unique properties, these sensors can quantify the basic tastes of saltiness, sourness, bitterness, umami, astringency and richness without multivariate analysis or artificial neural networks. This review describes all aspects of these taste sensors based on artificial lipid, ranging from the response principle and optimal design methods to applications in the food, beverage, and pharmaceutical markets.

It is possible to evaluate the taste of foods or medicines using a taste sensor. The taste sensor converts information on taste into an electrical signal using several lipid/polymer membranes. A lipid/polymer membrane for bitterness sensing can evaluate aftertaste after immersion in monosodium glutamate (MSG), which is called "preconditioning". However, we have not yet analyzed the change in the surface structure of the membrane as a result of preconditioning. Thus, we analyzed the change in the surface by performing contact angle and surface zeta potential measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS) and gas cluster ion beam time-of-flight secondary ion mass spectrometry (GCIB-TOF-SIMS). After preconditioning, the concentrations of MSG and tetradodecylammonium bromide (TDAB), contained in the lipid membrane were found to be higher in the surface region than in the bulk region. The effect of preconditioning was revealed by the above analysis methods.

This paper reports a new measurement method to detect ppb levels of noncharged organic substances using lipid/polymer membrane sensors. Noncharged organic substances have large influences on the adsorption of positively-charged lipids to negatively-charged membranes. Organic solvents (trichloroethylene) and endocrine disrupting chemicals (di-2-ethylhexylphthalate) were detected by utilizing the sensor output, which is the change of membrane potential caused by interactions among the lipid membrane, noncharged organic substances, and lipids in solution. This new potentiometric method has a possibility of detection of a trace amount of noncharged toxic substances.

This paper describes an application of taste sensor for detection of a trace amount of organic substances. This sensor consists of multichannel sensors with lipid membranes which are modeled on living organisms. One of characteristics of this sensor is a global selectivity. We discovered that organic substances have large influences on the adsorption of a plus charged lipid (additive in a solution) to a lipid membrane made by minus charged lipid. Using this method, some of organic substances, such as oil, Trichioroethylene and Di-2-ethylhexylphthalate, could be detected about 100ppb within five minutes. In conclusion, the taste sensor has a possibility for real-time monitoring of water quality using this new methods.

This paper describes an application of taste sensor for detection of cyanide. The taste sensor consists of multichannel sensors with lipid membranes which are modeled on living organisms. One of characteristics of this sensor is a global selectivity. In this study, we have developed a new effective method which is able to control the charge of membranes for high sensitivity and selectivity of lipid membrane sensors. Using this method, sensors for free cyanide and complex cyanide were developed. We could detect total cyanide under the guideline limit. It was possible to detect free cyanide below the concentration 0.5ppm in river water. Measurement time is within five minutes. In conclusion, the taste sensor has a very powerful performance and advantage for real time monitoring of water quality.

Detection of some toxic substances in water is a time consuming process because large number of substances need to be analyzed. When some toxic substances in the drains flow into the river, they cause environmental destruction. Accurate detection of substances which have serious effects on living organism is required as well as short measurement time. Although a sensing system employing living fish is devised, there are some problems in reliability, maintenance and evaluation because they are living thing. It is possible to measure the influence of pollutant for living organism directly by a sensor which is similar to biological systems. So we investigate a method of detection of toxic substances by multichannel lipid membrane sensors which are modeled on living organism.SA401 has multichannel sensor with lipid membranes which are modeled on living organism. It is able to detect some toxic substances in the water. For the reason, this system has been applied to measure water quality, such as, mineral water, tap water, contaminated river water and factory drains. We have found this method is effective and many pollutants (e. g. CN-, Fe3+, Cu2+, etc.), in factory drains, have been measured in a few minutes, the detection limits are lower than regulations of drain. It is possible to detect cyanide of factory drains selectively in short time by applying lipid membrane sensor. In conclusion, it is an effective mean to use multichannel lipid membrane sensors for observation of water quality especially for factory drains.

Outgassing rates and optical absorption coefficients of five kinds of black colored coatings, i.e. Ultra-Black NiP (UB-NiP), Phos-black II, Raydent, diamond-like-carbon formed on electrochemical buffed SS surface (ECB+DLC) and Alumite, have been examined to be used as an optical absorber in the high vacuum system of interferometric gravitational wave detectors. The outgassing rate and optical absorption coefficient of UB-NiP were q = 2.2×10-5 t -1.2 [Pa m3/sec/m2] (0.2≤t [hour]≤100) and 99.89% for 1064 nm in wavelength, respectively. These are considered as high performances. ECB+DLC had the optical absorption coefficient of 65% and its outgassing rate was two orders of magnitude lower than that of UB-NiP. It is concluded that UB-NiP is suitable for coating on small optical devices such that high efficiency of optical absorption was required. On the contrary, ECB+DLC coating is useful when it is applied to devices having a large area.

This paper describes a measurement method to detect a ppb level of agricultural chemicals within five minutes using a lipid/polymer membrane sensor. Noncharged organic substances have large influences on the adsorption of positively charged lipids to negatively charged membranes. In this study, noncharged agricultural chemicals in the washed vegetables (spinach, broccoli and Japanese basil) solution can be detected. These substances can be detected above 2000 ppb in these solutions. In the case of spinach and broccoli, it can be considered that agricultural chemicals inhibit the adsorption of the adsorbent in solution to the positively charged lipid membrane, because the change rate is below zero. In the case of Japanese basil the agricultural chemicals have a synergetic effect on the adsorption of the adsorbent to the lipid membrane. These results show that noncharged agricultural chemicals can be detected indirectly. We obtained a possibility that agricultural chemicals can be classified before an accurate chemical analysis. It is useful for the evaluating safety of vegetables and fruits.

Describes a measurement method to detect ppm level of noncharged agricultural chemicals using a lipid/polymer membrane sensor within five minutes. In the case of this new measurement method, non-charged toxic substances are detected indirectly. Sensor output is change of membrane potential caused by interaction among lipid membrane, agricultural chemicals and lipid in a solution. This, method has a possibility of detection of a trace amount of agricultural chemicals. It is useful for the evaluation of safety of vegetables and fruits.

This paper describes a new preparation process of highly densified bodies of a γII-Li3.4Si0.4V0.6O4 solid solution, which is the best lithium ion conductor among those containing silicates, via sintering a xerogel powder derived from alkoxides. The xerogel powder consisting of spherical, amorphous aggregates was prepared by hydrolysis of alcoholic solutions of Si(OC2H5)4, VO(OC2H5)3 and LiOC2H5 at 70°C, followed by drying. The diameter was smaller than 0.1μm. The powder crystallized gradually into the βII-solid solution with poor crystallinity above 500°C, and a γII-solid solution appeared above 650°C. The highly densified bodies of the γII-solid solutions were obtained by sintering the compact of the xerogel powder at a relatively low temperature, 900°C. The sintered bodies consisted of only the γII phase and contained no other phases such as Li2SiO3 which forms as a result of Li2O evaporation during sintering. This method lowered the sintering temperature by 150°C compared with that for the conventional method. The ionic conductivities of the sintered bodies were determined by analysing their complex impedance diagrams in the frequency range of 5Hz-13MHz. The sintered bodies prepared by the conventional method were characterized by the presence of two distinct semicircles in the complex impedance diagram; one corresponds to AC response of the grain (bulk) and the other to that of the grain boundaries. However, the sintered bodies prepared by this method indicated only a single semicircle due to AC response of the grain. The total ionic conductivity of the sintered bodies, 3.4×10-5Scm-1 at 25°C rising to 4.7×10-3Scm-1 at 150°C, was about three times higher than that of the those prepared by the conventional method due to negligible grain boundary resistance.