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.
Five basic tastes identified by different receptors
on the tongue are salty, sweet, bitter, sour and
savory.
Background

3.  Used primarily for food and beverage quality analysis
 Quantification vs qualitative
 Smaller and more economical
 Parts of the ET
 5 metal working electrodes which allow current to pass through the
sample solution (Gold, iridium, rhodium, palladium, and platinum).
 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

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

5. 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

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

7.  Basic Taste Test
 Tool to visualize the way the ET distinguishes between
different flavors
Methods

8. 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

9.  Large Amplitude Pulse Voltammetry applied to
Tea samples
 Applies voltage in in different steps to the system to measure
the resulting current with each application
 10 samples of tea
 5 trials each
 Each working electrode is individually accessed in the
cell
Methods

10. 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

11. 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.

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 transferred the highest amount of
charge and had the highest strength of response.

13. Discussion and Future Research
 Clustering of Samples
 Accuracy of results
 Different Manufacturing Dates
 Less clustering in tea samples because of higher
variability
 Applications

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