Beta-cyclodextrin/surface plasmon resonance detection system for sensing bitter-astringent taste intensity of green tea catechins.

To develop a methodology for creating a sensor with a receptor for specific taste substances, we focused on constructing a sensing system for the bitter-astringent taste intensity of green tea catechins: (-)-epigallocatechin-3-O-gallate (EGCg), (-)-epicatechin-3-O-gallate (ECg), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC). (1)H NMR titration experiments revealed that beta-cyclodextrin was an adequate receptor for sensing the bitter-astringent taste intensity of catechins. A surface plasmon resonance (SPR) system immobilized beta-cyclodextrin indicated larger responses for the gallate-type catechins in comparison to the non-gallate-type catechins. These responses corresponded to the tendency of the bitter-astringent taste intensity of the catechins felt by humans. Furthermore, the SPR system detected the larger stability of the complex between the gallate-type catechins and beta-cyclodextrin, which was interpreted as the aftertaste produced in humans by the gallate-type catechins. These results demonstrate that the beta-cyclodextrin/SPR system can sense the bitter-astringent taste intensity of the green tea catechins similar to human gustation. The methodology presented in this study can be used as a basic strategy for developing taste sensors with specific receptor functions.

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.

Evaluation of the astringency of black tea by a taste sensor system: scope and limitation.

Grading the astringency of black tea by a taste sensor system was studied. The black tea samples manufactured in India and Sri Lanka were classified into ten steps on the basis of two standard solutions (0.65 mM and 0.26 mM EGCg aqueous solutions). An organoleptic test demonstrated that the sensor output was correlative to the human gustatory sense.

Techniques for universal evaluation of astringency of green tea infusion by the use of a taste sensor system.

A practical method for universal evaluation of the astringency of green tea infusion by a taste sensor system was established. The use of EGCg aqueous solution as a standard enabled analysis with high accuracy and reproducibility. The sensor output was converted into taste-intensity on the basis of Weber's and Weber-Fechner laws, which was named the "EIT(ast)" value ("EIT" and "ast" are abbreviations for "Estimated Intensity of Taste" and "astringency" respectively). It was clarified that green tea infusion is to be classified into eight grades on the EIT(ast) scale. Furthermore, the high correlation of the EIT(ast) value with the human gustatory sense and the high stability of the taste sensor were proved.