Identification of varying grades of black tea using a

voltammetric electronic tongue

Malini Basu11th Grade

Pine Crest School

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

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

Voltammetric ET

Working Electrodes

Reference electrode

Counter electrode

Top view

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

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

Objective

Basic Taste Test Tool to visualize the way the ET distinguishes

between different flavors

Methods

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

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

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

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.

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.

Discussion and Future Research

Clustering of Samples

Accuracy of results

Different Manufacturing Dates

Less clustering in tea samples because of

higher variability

Applications

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