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TRANSCRIPT
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