Objective evaluation methods for the bitter and astringent taste intensities of black and oolong teas by a taste sensor

In order to objectively indicate the bitter taste intensities of black and oolong teas on the basis of a permanent standard point, a taste sensor method was developed that calibrated the sensor outputs with standard solutions prepared with only pure chemicals. Ethyl gallate (EG) was used as the standard substance. The sensor outputs were converted into the bitter taste intensities using two EG solutions at different concentrations. The astringent taste intensities of these teas were evaluated by the similar method. In this case, (-)-epigallochatechin-3-O-gallate (EGcg) was used as the standard substance. These evaluation results by the taste sensor system showed a similar tendency as those by human gustatory sense. Relative standard deviations of the sensor results revealed that these evaluation methods possessed enough practical precisions. Two-dimensional mapping analysis of the bitter and astringent taste intensities showed that, as a whole, the taste intensities of the Indian and Sri Lankan black tea samples had a tendency to be stronger than those of the Chinese oolong tea samples under the sample preparation conditions in this study. (C) 2013 Elsevier Ltd. All rights reserved.