Evaluation of Astringent Compounds Using Electronic Tongue Technology

The electronic tongue (E-tongue) is an emerging technology that enables the rapid and objective evaluation of various astringent compounds. This study investigated E-tongue measurements and human sensory evaluation to analyze the concentration-dependent astringency responses of seven compounds. Difference analysis, principal component analysis (PCA), and cluster analysis were applied to differentiate the compounds based on their taste profiles. The results revealed distinct relationships between E-tongue response values and concentration. Specifically, epigallocatechin gallate (EGCG) and epigallocatechin (EGC) exhibited positive correlations with concentration, whereas tea polyphenols, tannic acid, and procyanidin showed negative correlations. In contrast, gallic acid and chlorogenic acid produced weak astringency responses. Difference analysis demonstrated significant taste variations across concentrations; PCA and cluster analysis further validated the E-tongue's capability for distinct discrimination of astringent compounds. Regression analysis between E-tongue measurements and human sensory scores demonstrated strong correlations for EGCG, EGC, tea polyphenols, tannic acid, and procyanidin, with procyanidin and EGCG exhibiting the best linearity. Predictive models achieved high accuracy (R ² > 0.9, RMSE < 10%) in validation, demonstrating the E-tongue's reliability as an alternative to sensory evaluation for astringency assessment.