This document describes using a voltammetric electronic tongue to identify varying grades of black tea. The electronic tongue uses 5 metal electrodes to analyze tea samples by measuring the current passed through the solutions. 10 black tea samples of different grades were tested, and the results showed the electronic tongue could distinguish the grades based on the strength of electrical response, with the highest quality tea having the strongest response. The technique was able to reliably differentiate the tea grades over multiple trials, demonstrating the potential of electronic tongues for food and beverage quality analysis applications.

1. Identification of varying grades of
black tea using a voltammetric
electronic tongue
Malini Basu
11th
Grade
Pine Crest School

2. Gustatory system in humans consists of direct
chemoreceptors called taste buds
Taste buds, located in groups in taste papilla are activated
in response to stimuli in solid and liquid foods
Background

3. Background
Five basic tastes identified by different receptors on the tongue are
salty, sweet, bitter, sour and savory
Half of the papilla on the tongue are sensitive to all the basic tastes
Half are sensitive to only one kind of taste
When a food molecule comes into contact with a taste bud, it
induces a chemical response that triggers stimuli in the nervous
system to alert the brain of a taste

4.  Used primarily for food and beverage quality analysis
 Allows for the quantification of quality analysis
 Smaller and more economical than methods such as gas chromatography,
mass spectroscopy, and high performance liquid chromatography
 Parts of the ET
 5 metal working electrodes which allow current to pass through the sample solution
(Gold, iridium, rhodium, palladium, and platinum)
 Using a variety of metal electrodes takes into consideration any reactive ion species in
solution
 Stainless steel counter electrode through which the current flows out of the sample
 Ag/AgCl is the reference electrode to which the electric potential between the
working and counter electrode is compared
 This electrode consists of a thin Ag wire surrounded by AgCl solution
Voltammetric Electronic Tongue

5. Voltammetric ET
Working
Electrodes
Reference
electrode
Counter
electrode
Top view

6. Tea
 Important commodity especially in Asian country
 Quality depends on Polyphenol concentrations
 Theaflavins (TF) and Thearubugins (TR) are the two groups of polyphenols that affect tea flavor significantly
 Processing
 Oxidation is the most important process
 Oxidized polyphenols affect tea flavor
 Physical damage to cell walls in previous steps allows for enzymes within the cell walls to stimulate oxidation.
 Oxidation of polyphenols creates the defining characteristics of different tea varieties.
 Converting polyphenol catechins to TF and TR
 Amount of oxidation defines quality of tea
 The tea industry has expert panels who assign different grades based on tea
quality
Catechin

7.  To identify the Electronic Tongue’s capability of differentiating
between 10 samples of varying grades of Black Tea.
Objective

8.  Basic Taste Test
 Tool to visualize the way the ET distinguishes between
different flavors
 Large Amplitude Pulse Voltammetry applied to
basic taste inducing solutions and tea samples
 Applies voltage in in different increments to the system to
induce different current values
 10 samples of tea
 5 trials each
 Each working electrode is individually accessed in the cell
Methods

9. 1.O M Basic Taste Test Solutions
Taste Compound Example
Sweet Sucrose: C12H22O11 Candy
Salty Sodium Chloride: NaCl Salted potato chips
Bitter Sodium Hydroxide: NaOH Caffeine in coffee
Sour Citric Acid: C6H8O7 Lemons
Umami (Savory) Glutamic Acid: C5H9NO4 Red Meat

10. Strength of Response vs. Charge of
Basic Taste Solutions
Demonstration of the ET’s ability to distinguish between the 5 basic tastes as well as water as
a ‘neutral’ taste. The clustering of each of the 5 trials establishes the accuracy of these results.
At about 4.5 uC of charge
the average strength of
response was 6,700 for the
NaOH solution (bitter)
NaCl
(salty)
C6H8O7
(Sour)
C5H9NO4
(Savory)
C12H22O11
(sweet)
H2O

11. Sample Number Grades
1 7/13 DM – Dust Mixed
2 BP – Broken Pekoe
3 PF – Pekoe Fannings (highest quality)
4 D – Dust (lowest quality)
5 8/13 DM – Dust Mixed
6 BP – Broken Pekoe
7 PF – Pekoe Fannings
8 D – Dust
9 10/13 DM – Dust Mixed
10 BP – Broken Pekoe
Tea Samples

12. Strength of Response vs. Total Charge of 10
Black Tea Samples
Insight into the varying strengths of the different grades of tea. The highest quality (PF,
sample 7) is located the right hand corner which shows it had the strongest charge and had the
highest strength of response.
Sample
Number
Grades
1 7/13 DM
2 BP
3 PF (highest quality)
4 D (lowest quality)
5 8/13 DM
6 BP
7 PF
8 D
9 10/13 DM
10 BP

13. Discussion and Future Research
 Clustering of Samples relates the reliability of the results over a series of five trials
 Different Manufacturing Dates may account for the varying results among the same tea sample
 Less clustering in tea samples compared to basic taste inducing solutions because of higher
variability
 Tea consists of numerous redox active polyphenols whereas the basic taste solutions were
composed of one compound
 Other applications
 Water quality analysis
 Food contamination
 Quantification of taste-masking ability different forms of oral medications such as capsules
and tablets

14. Resources
 “Electronic Tongue” Mousumi Palit (2008).
 “An electronic tongue based on voltammetry” Elsevir, Winquist et al. (357, 21 – 31) 1997
 “Discrimination of tea by means of a voltammetric electronic tongue and different applied waveforms” Elsevier, Ivarsson et al.
(76, 449 – 454) 2001.
 Palit, M.; Tudu, B.; Dutta, P.K.; Dutta, A.; Jana, A.; Roy, J.K.; Bhattacharyya, N.; Bandyopadhyay, R.; Chatterjee, A., "Classification
of Black Tea Taste and Correlation With Tea Taster's Mark Using Voltammetric Electronic Tongue," Instrumentation and
Measurement, IEEE Transactions on , vol.59, no.8, pp.2230,2239, Aug. 2010
 Tudu B, Jana A, Bandyopadhyay R. “Instrumental testing of tea by combining the responses of electronic nose and tongue”
Elsevir vol 110. (356-363) 2012
 http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072592/

15. Thank You!