Masaaki Habara

Advanced Taste Sensors Based on Artificial Lipids with Global Selectivity to Basic Taste Qualities and High Correlation to Sensory Scores

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.

Development and Evaluation of a Miniaturized Taste Sensor Chip

A miniaturized taste sensor chip was designed for use in a portable-type taste sensing system. The fabricated sensor chip (40 mm × 26 mm × 2.2 mm) has multiple taste-sensing sites consisting of a poly(hydroxyethyl methacrylate) hydrogel with KCl as the electrolyte layer for stability of the membrane potential and artificial lipid membranes as the taste sensing elements. The sensor responses to the standard taste substances showed high accuracy and good reproducibility, which is comparable with the performance of the sensor probe of the commercialized taste sensing system. Thus, the fabricated taste sensor chip could be used as a key element for the realization of a portable-type taste sensing system.

Study of surface-modified lipid/polymer membranes for detecting sweet taste substances

A taste sensor with lipid/polymer membranes was developed in this study for detecting sweet taste substances. The lipid membrane was modified with gallic acid (3,4,5-trihydroxybenzoic acid) to enhanced the sensitivity to sugars. The result from the absorption spectra obtained from UV spectrum measurements and potentiometric measurements with the taste sensor indicated that the pKa and the steric structure of the phenolic compounds play an important role for the potential change of the taste sensor on sugars.

The Utility of the Artificial Taste Sensor in Evaluating the Bitterness of Drugs: Correlation with Responses of Human TASTE2 Receptors (hTAS2Rs)

The purpose of this study was to examine the ability of the artificial taste sensor to evaluate the bitterness of drugs by comparing the responses of the taste sensor with documented responses of human TASTE2 receptors (hTAS2Rs). For this purpose 22 bitter compounds, used as ingredients of pharmaceutical medicines in Japan and known ligands of hTAS2Rs, were selected for testing. Their solutions (0.01, 0.03, 0.1 mM) were evaluated by five different taste sensors (AC0, AN0, BT0, C00, AE1). Correlations between physicochemical parameters of the compounds and the responses of the taste sensors and hTAS2Rs were evaluated. From taste sensor measurements, diphenidol, haloperidol, diphenhydramine, dextromethorphan and papaverine, all ligands of hTAS2R 10 and/or hTAS2R14, were predicted to express strong bitterness, surpassing that of quinine. Responses of taste sensors BT0 were found to be significantly correlated with responses of hTAS2R14. High log P values (≧2.73) and responses of hTAS2R14 were also significantly correlated (** p<0.01, chi-square test). In conclusion, taste sensor BT0 is highly sensitive to bitterness and correlates significantly with hTAS2R14, making it useful for evaluating the bitterness of hydrophobic compounds which respond to hTAS2R14 and their inhibitors.

Development of sweetness sensor for high-potency sweeteners using lipid polymer membrane

High-potency sweeteners are applied to low-calorie diets and bitterness-masking ingredients in pharmaceutical products. We have studied taste sensors with lipid polymer membranes based on potentiometric measurement system for high-potency sweeteners. However, the sensor also responds to astringency substances because of hydrophobic characteristics of the lipid polymer membrane. In this study, we developed a new taste sensor using a lipid polymer membrane for saccharin sodium and acesulfame potassium as negatively charged high-potency sweeteners. We optimized the quantities and types of lipids and plasticizers for the fabrication of the sensor with high selectivity and sensitivity. We succeeded in the fabrication of the new sensor, the output of which could be suppressed under −5 mV for astringency substances. Moreover, the sensor has a good sensitivity and selectivity for saccharin sodium and acesulfame potassium.

Influence of alkyl chain length of lipid in caffeine detection using taste sensor with lipid/polymer membranes

The taste sensor was widely used in distinguishing various taste substances. However, the taste sensor has poorer sensitivity to uncharged molecules such as caffeine, a bitter substance, than to charged taste substances. In the present study, we discussed the sensitivity of caffeine detection using a taste sensor with lipid/polymer membranes that were formed with different length of methyl group of lipid, namely, tetra-n-ctylammonium bromide (R8), tetrakis-(decyl)-ammonium bromide (R10), tetradodecylammonium bromide (TDAB; R12), and tetrahexadecylammonium bromide (R16). As a result, we observed that the electric responses of the lipid membranes to caffeine were associated with the length of alkyl chain of a lipid and an optimum concentration of the lipids in membranes was also observed to enhance the sensitivity of caffeine with taste sensor.