A hand-held electronic tongue based on fluorometry for taste assessment of tea.
A hand-held electronic tongue was developed for determining taste levels of astringency and umami in tea infusions. The sensing principles are based on quenching the fluorescence of 3-aminophthalate by tannin, and the fluorogenic reaction of o-phthalaldehyde (OPA) with amino acids to determine astringency and umami levels, respectively. Both reactions were measured by a single fluorescence sensing system with same excitation and emission wavelengths (340/425 nm). This work describes in detail the design, fabrication, and performance evaluation of a hand-held fluorometer with an ultra-violet light emitted diode (UVLED) and a photo-detector with a filter built-in. The dimension and the weight of proposed electronic tongue prototype are only 120×60×65 mm(3) and 150 g, respectively. The detection limits of this prototype for theanine and tannic acid were 0.2 μg/ml and 1 μg/ml, respectively. Correlation coefficients of this prototype compared with a commercial fluorescence instrument are both higher than 0.995 in determinations of tannin acid and theanine. Linear detection ranges of the hand-held fluorometer for tannic acid and theanine are 1-20 μg/ml and 0.2-10 μg/ml (CV<5%, n=3), respectively. A specified taste indicator for tea, defined as ratio of umami to astringency, was adopted here to effectively distinguish flavour quality of partially fermented Oolong teas.
Chang
Kuang-Hua
KH
Department of Bio-industrial Mechatronics Engineering, College of Bio-Resources and Agriculture, National Taiwan University, Taipei, Taiwan.
Chen
Richie L C
RL
Hsieh
Bo-Chuan
BC
Chen
Po-Chung
PC
Hsiao
Hsien-Yi
HY
Nieh
Chi-Hua
CH
Cheng
Tzong-Jih
TJ
D015374:Biosensing Techniques / Q000295:instrumentation*; D004867:Equipment Design; D005285:Fermentation; D005470:Fluorometry / Q000295:instrumentation*; D005971:Glutamates / Q000032:analysis; D006801:Humans; D013634:Tannins / Q000032:analysis; D013649:Taste; D013662:Tea / Q000737:chemistry*; D014059:Tongue
D005971:Glutamates; D013634:Tannins; D013662:Tea; C026166:theanine