TECHNICAL SEMINAR ON

“TASTE SENSORS or ELECTRONIC TONGUE”

A technical seminar report submitted in partial fulfillment of the requirement for the Degree of Bachelor of Technology

Under BPUT

ByName: Shekhar Suman Mohanty

Regd. No: 0801289013Branch: Electronics & Telecommunication

Year: 2011-2012

1TRIDENT ACADEMY OF TECHNOLOGY

BHUBANESWAR

DEPT. OF ELECTRONICS & TELECOMMUNICATION ENGINEERING.

TRIDENT ACADEMY OF TECHNOLOGY, BHUBANESWAR

CERTIFICATE

This is to certify that Shekhar Suman Mohanty , bearing Regd. No.

student of 8thsemester,Branch: Electronics and Telecommunication

Engineering, Trident Academy of Technology, Bhubaneswar have

submitted seminar report on “TASTE SENSORS or ELECTRONIC

TONGUE”. This is required for the fulfillment for Bachelor’s Degree in

Electronics & Telecommunication Engineering under BPUT.

Seminar coordinator Head of the Dept.

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I take this opportunity to express my hearty thanks to all those who individually as well

as collectively helped me in the successful completion of this seminar.

I would like to express my immense gratitude and sincere thanks to Prof. Subhendu

Kumar Behera, whose co-operative guidance has helped me in successful completion of

this seminar on “TASTE SENSOR OR ELECTRONIC TONGUE”. I am very much

thankful to Professor Mrs(Dr).Sakuntala Mahapatra (HOD, Dept. of Electronics) and

seminar coordinator Asst. Prof. Rabindra Bhojray for helping me to complete the

seminar successfully. .

I express my deep sense of gratitude and appreciation to the entire faculty members in

Dept. of Electronics& Telecommunication for their valuable and scholarly guidance,

constant supervision and timely advice and non-teaching staff of the Dept. of

Electronics & Telecommunication and my friends without whom my endeavors

wouldn’t have been successful.

Name: Shekhar Suman Mohanty Branch: ETC(A) Regd. No: 0801289013

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ABSTRACT

TASTE SENSOR ‘ELECTRONIC TONGUE’

The Electronics Sensor Technology uses non obtrusive sensing methods, employing its uses in very vital applications in industries. Taste Sensors, also known as Artificial or Electronic tongues, measure and compare taste. These provide a quantitative and objective scale and find applications in food, beverages and pharmaceuticals industries .The liquid samples are directly analyzed without any preparation, whereas solids require preliminary dissolution before measurement. Reference electrode and sensors are dipped are dipped for 120 seconds in a beaker containing a test solution. A potentiometric difference between each sensor and a reference electrode is measured by means of a measuring device and recorded by an e-tongue software. Depending on the recorded reading, five taste sensations namely, sweet, bitter, salty, savory and sour can be distinguished. These are used for analyzing flavor ageing in beverages, Detect undesirable, harmful, toxics and taints, Analyzing medicine stability in terms of taste etc.

Submitted By:- Name: Shekhar Suman

Mohanty Regd. No.:

0801289013

Roll No.: 03, 7th

Semester Branch: ETC (A)

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CONTENT

1. INTRODUCTION ………………………………………………….. 01

2. HUMAN TONGUE………………………………………………….04

3. CORRELATION BETWEEN HUMAN TONGUE AND

TASTE SENSOR…………………………………………………….12

4. WHAT IS HUMAN TONGUE ???......................................................13

5. HISTORY…………………………………………………………….14

6. SYSTEM ATTRIBUTES…………………………………………….19

7. MECHANISME AND WORKING…………………………………. 21

8. ADVANTAGES AND DISADVANTAGES………………………...25

9. APPLICATION OF ELECTRONIC TONGUE……………………...26

10. CONCLUSION……………………………………………………...29

11. REFERENCE………………………………………………………..30

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INTRODUCTION

Since our childhood we know that there are five senses in our body. They are the most important

things in our life because without sensory organs we can’t even think of a normal life .Just think of

a life without any of the sense and it becomes devastating. We human basically have five senses

i.e. nose to smell, eyes to see, ears to listen, skin to feel the touch & tongue to taste.

As we know that all those sensory organ has their part to do in our life such as when we smell a

thing we tend to use our nose similarly for the rest of the sensory organs but in due course of life

we tend to neglect the importance of some of the sense organs such as taste which is sensed by

tongue. Tongue is one of the most important organs of human which enables us taste different

flavour of different things we eat or try to know through taste.

Taste refers to the ability to detect the flavor of substances such as food, certain minerals, and

poisons, etc. Humans receive tastes through sensory organs called taste buds, or gustatory

calyculi, concentrated on the upper surface of the tongue. The sensation of taste can be

categorized into five basic tastes: sweet, bitterness, sour, salty, and umami. The recognition and

awareness of umami is a relatively recent development in Western cuisine. MSG produces a

strong umami taste. As taste senses are both harmful and beneficial things, all basic tastes are

classified as either appetitive or aversive, depending upon the effect the things they sense have

on our bodies. The basic tastes that are here to concontribute only partially to the sensation and

flavor of food in the mouth other factors include smell, detected by the olfactory epithelium of

the nose; texture, detected through a variety of mechanoreceptors, muscle nerves, etc.;

temperature, detected by thermoreceptors, and spiciness or piquance also called Chemesthesis

With the advancement in Electronics Engineering, Sensors have made

their through to very vital applications in industries. A sensor is a device

that changes various types of physiochemical properties of a target to a

different state, usually electrical signals. We have various types of

Sensors such as Motion Sensors, Seismic Sensors, Taste Sensors, etc.

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WHAT IS TASTE?

In its first definition, the American Heritage Dictionary limits the tastes perceived by the taste

buds to four; in fact there are at least six — in addition to the classic four, there is the taste of fat,

and a taste called umami. “Umami” means delicious in Japanese, and is the word for the savory

taste of meat. In fact, our taste buds are designed to tell us about the nutritional qualities of the

food we eat: sweet for ripe fruits and carbohydrates, sour for unripe fruit and vitamin C, salty for

salt and other minerals, bitter for poisonous plants, umami for protein, and fat.

The second definition is the one most people have in mind when they talk about the taste of a food

— taste, in this sense, means flavor. Better than any of the other

components of flavor, smell allows us to determine the specific

food we are eating, for example to distinguish a lemon from a

lime. In fact most people can distinguish among 1000 odors, and

perfumers among as many as 10000!

Taste is a survival mechanism, alerting us to potentially harmful or potentially nutritious

substances. The receptors for taste sensation are located in the taste buds. There are nearly 10,000

taste buds located on the tongue of young adults and a few are found on soft palate, inner surface

of cheeks, pharynx and epiglottis. Each taste bud is an oval body consisting of three kinds of

epithelial cells: supporting cells, gustatory cells and basal cells. The gustatory system generally has

two basic functions. The first is the clear distinction between the nutritive and beneficial

compounds and the second is the detection of potentially harmful or toxic substances. Taste

receptor cells must be able to detect wide range of tastes from simple ions to complex molecules.

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WHAT IS A SENSOR?

A sensor (also called detector) is a device that measures a physical quantity and converts it into a

signal which can be read by an observer or by an instrument. For example, a mercury-in-glass

thermometer converts the measured temperature into expansion and contraction of a liquid which

can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage

which can be read by a voltmeter. For accuracy, most sensors are calibrated against known

standards.

There are many types of sensors used for various applications that detect different types of

measurands i.e. Chemical, Thermal, environmental, metrological, taste, smell, touch etc.

There are inventions or devices that can extend the human physical senses of sight, hearing,

taste, smell, touch (pressure, temperature and gravity). And to appreciate the role of the

environmental sensors by considering them as an extension of human senses. Sensors sense the

same phenomena as human senses, but:

They are there 24 hours a day

They are there 365 days a year

Their measurements are more precise (sensitive & selective)

Their measurements are reproducible

Your senses consist of a very narrow band of what is possible, but there are devices that help

people sense things beyond their capabilities or limitations.

Each of our senses needs a certain amount of energy to work properly

1. Light must be a certain brightness to see.

2. Sound must be loud enough to hear.

3. The pressure on our skin must be great enough to feel. The skin must be

sensitive enough to detect the difference in temperature hot or cold.

Some of the types of sensors are:-

Artificial nose

Smoke detector

Microphones

Ultrasound devices

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X-RAY machines

Night vision goggles

Electronic Tongue

Magnetic field sensors(Compasses)

Electric field sensors(Electrometers)

Thermometer

Litmus paper

Security appliances

Traffic Lights

Cell phones

Motion sensors

There are environmental parameters that are important to our welfare and survival that cannot be

sensed by the human senses. For example: Radioactivity, UV Exposure, Carbon monoxide,

radon etc. As a result sensors have became an indespensible part of our life in a very small

period of time.

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HUMAN TONGUE

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which

manipulates food for mastication. It is the primary organ of taste (Gustation), as much of the

upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by

saliva, and is richly supplied with nerves and blood vessels. In humans a secondary function of

the tongue is phonetic articulation. The tongue also serves as a

natural means of cleaning one's teeth. The ability to perceive

different tastes is not localised in different parts of the tongue, as

is widely believed. This error arose because of misinterpretation

of some 19th century research. The human tongue consist of two

types of muscular part they are called as extrinsic muscles and

intrinsic muscles.

What are taste sensors or taste buds?

Human tongue that perceives taste is made up of cells. Taste papillae can be seen on the tongue as

little red dots or raised bumps, particularly at the front of the tongue. Taste buds are a collection of

cells on these papillae; the buds are generally invisible by the naked eye. The cell's skin, biological

membrane, consists of a double layer of lipid molecules and proteins. Lipids are oil-like substances

contained in our bodies. Lipids are made up of the water loving (hydrophilic) part and the water

hating (hydrophobic) part. There is a lot of water in both the inside and outside of the cell and

hence lipid molecules make up a double layer on the

biological membrane, with the hydrophilic part facing the

inside and outside of the cell. In water, the membrane is

electrically charged because the hydrophilic parts of lipid

molecules are ionizing. Also, the inside and outside of the cell

are full of different concentrations of salt-like substances

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Taste receptors can be categorized (on the basis of taste perception) into five primary categories:

Sweet, Sour, Salt, Umami and Bitter. Sweet receptors respond to substances such as sugar,

saccharin and some amino acids.

Sour receptors respond to hydrogen ions (H+) or acidity of the solution. Salty and Bitter

receptors respond to metal ions in solution and alkaloids respectively.

Umami (“Delicious”), a taste discovered by the Japanese, is elicited by the amino

acids.Glutamate which appears to be responsible for the “beef

taste” of steak and the flavor of

monosodium glutamate, a food additive.

ARTIFICIAL TASTE SENSOR

Artificial taste sensor is an intelligent electronic cum biophysical device that could be explored

to artificially reproduce the sense of taste, which is otherwise a complex, comprehensive sense of

man. Several kinds of foodstuffs, mineral waters and pharmaceutical formulations could be

discriminated /differentiated easily using the taste sensor. Different electric potentials generated

by chemical substances after interaction with the lipid/polymer membrane of the taste sensor is

the basis of taste discrimination by the sensor. Hence, the taste sensors can be considered as a

valuable tool in the evolution of bitterness intensity in function of time, which is essential in the

selection of an optimal formulation. In the present study we have tried to explain the theory,

composition and functioning of a taste sensor along with the potential applications of the same.

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CORRELATION BETWEEN HUMAN TONGUE AND TASTE SENSORS

Artificial tongue and a human tongue have a lot in common their processing style and procedure

are almost equal. Both the human tongue and artificial tongue work on the following process:-

Acquisition

Data processing

Results

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WHAT IS A ELECTRONIC TONGUE?

Taste has an important role in the development of oral pharmaceuticals, with respect to patient

acceptability and compliance, and is one of the prime factors determining the market penetration

and commercial success of oral formulations, especially in pediatric medicine. Hence,

pharmaceutical industries invest time, money and resources into developing palatable and

pleasant-tasting products and industries adopt various taste-masking techniques to develop an

appropriate formulation. Taste assessment is one important quality-control parameter for

evaluating taste masked formulations. Any new molecular entity, drug or formulation can be

assessed using in vitro or in vivo methods for taste. In vivo approaches include human taste panel

studies, electrophysiological methods and animal preference studies. Several innovative in vitro

drug release studies utilizing taste sensors, specially designed apparatus and drug release by

modified pharmacopoeia methods have been reported in the literature for assessing the taste of

drugs or drug

products. The multichannel taste sensor, also known as the electronic tongue is claimed to

determine taste in a similar manner to biological taste perception in humans.

A taste sensor with global selectivity is composed of several kinds of lipid/polymer membranes for

transforming information of taste substances into an electric signal. The output of this electronic

tongue shows different patterns for chemical substances which have different taste qualities, such

as saltiness and sourness. Such devices have been mainly used in the field of food analysis: for

classification of wine, beer, tea and herbal products, tomato samples, coffee, and milk. An

electronic tongue was also applied in the analysis of industrial samples (fermentation samples) and

in environment monitoring (water quality analysis, identification on toxic substances like heavy

metals and plant samples). Evaluation of a taste sensor instrument (electronic tongue) for use in

formulation development. The examples demonstrate the electronic tongue’s utility in

characterizing bitterness and taste masking of the bitterness.

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HISTORY

The artificial taste sensor, otherwise known as ‘Electronic Tongue’ has been used for the

estimation of food tastes by mimicking human gustatory system. It consists of an array of

sensing elements, and a data processing unit as an alternative for the human tongue and the brain

respectively. The sensing element consists of an array of transducers that are nonselective and

non-specific like that of human taste buds. The sensor array generates a pattern, which is in close

proximity with the characteristics of the samples analyzed.

Furthermore, such taste sensors have a global selectivity that has the potential to classify an

enormous range of chemicals into several groups on the basis of properties such as taste

intensities and qualities. A tool that has recently become available is the “electronic

tongue”. The electronic tongue, which was introduced in 1989 and which can be considered as a

promising device in quantitative and qualitative analysis of multispecies solutions. An

Electronic Tongue is an instrument which comprises of electrochemical cell, sensor array and

appropriate pattern recognition system, capable of recognizing simple or complex soluble

nonvolatile molecules which forms a taste of a sample. The

Sensor array consists of broadly tuned (non-specific) potentiometric metal based electrodes that

are treated with a variety of common anion of a salt in solution chemical materials.

In 1989 Hidekazu Ikezaki who was a researcher in the research laboratory of Anritsu corporation

(Japan), who is currently president of Intelligent Sensor Technology (Japan), launched research

and development on taste sensors collaboratively with Dr. Kiyoshi Toko who was an assistant

professor of Kyushu University at that time, who is now a distinguished professor of Kyushu

University. Also Mr.Kenshi Hayashi who was a graduate student of Kyushu University at that

time,who is now a professor of Kyushu University, and Dr. Prof. Satoru Iiyama of Kinki

University joined the research project to study it extensively.

Different types of taste sensors have been invented in the due course of time but has been

removed by the new one due to there advantage over the disadvantage of the previous one. Some

of the the successful taste sensors are :-

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Taste Sensing System SA401 (1993 to 1996)

Taste Sensing System SA402 (1996 to 2000)

Taste Sensing System SA402B (2000 to 2007)

Taste Sensing System TS-5000Z (2007 to present)

1. Taste Sensing System SA401 (1993 to 1996)

After around 4 years of the collaborative research between Anritsu corporation and Kyushu

University, we successfully developed the first commercial Taste Sensing System SA401 in

1993. A robot arm moved automatically to move to samples and to rinse taste sensors to be

attached to the tip of the arm. Analysis was processed in a simple manner using MS/DOS batch

files. Ten samples of 150 ml can be measured in a measurement with 7 types of taste sensors. At

that time if beer samples were measured, taste sensors needed to be directly immersed in a

sample of beer for stabilizing the sensor outputs, which was called the pre-conditioning method.

The SA401 was sold only in Japan, and around 10 units of them were introduced to laboratories

and national institutes. Iwate Institute Research Center, one of our customers, used the SA401

for evaluation of Japanese Sake, and Japanese Emperor Akihito and Empress Michiko came to

see the machine measuring there as the latest technology at the time.

2. Taste Sensing System SA402 (1996 to 2000)

To accept Windows95 widely used at the time, we developed Taste Sensing System SA402

which can be controlled by the computer of PC-9800

series developed by NEC. Also GUI, or Graphical User

Interface, for the operation and analysis applications

drastically was improved. The advantage of the above-

described pre-conditioning method was to enable

accurateand rapid because

all the membranes showed the same characteristics due

to the adsorption of taste substances on them.

15

To improve this, CPA measurement method was developed so much more information of tastes

can be obtained, consequently leading to the objective taste evaluation.

The SA402 was sold only in Japan and around 20 units of them were introduced.

3. Taste Sensing System SA402B (2000 to 2007)

In the late 1990s, following the production end of the

computers of PC-9800 series, we developed Taste

Sensing System SA402B applicable to IBM PC/AT

compatible computer. In addition, to respond the change

in OS Windows (98, Me, 2000 and XP), several minor

changes for the software in SA402B were made.

Since around 2003 we have succeeded in developing taste sensors with global selectivity using

innovative and unique sensor technologies. In addition, we have also developed new taste

evaluation method, taste information method, which provides a clear understanding of taste

qualities and intensities, without complicate multivariate analysis.

In 2006 we started selling overseas, and more than 100 units were introduced to customers

around the world.

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4. Taste Sensing System TS-5000Z (2007

to present)

The previous models of Taste Sensing

System were designed to be used as a

standalone instrument only for laboratory.

The latest model TS-5000Z, one of the

network systems, is designed for use both

in quality control and laboratory. A management server

runs on a Linux operating system with a reputation as

stable operation, and includes database in it to prevent the loss, destruction, falsification,

divulgation of measurement data. The database collects all of the data from some instruments via

LAN, allowing some users to simultaneously have access to it using a web browser for analysis.

More than 100 units have already been introduced to laboratories in various countries, including

Asia and Europe since 2007.

The technologically advanced taste sensors equipped with Taste Sensing System TS-5000Z

exhibit specialized ability - global selectivity -, and offer satisfactory results with high

correlation to sensory scores. This system offers you comprehensive and objective taste

evaluation of foods, beverages and pharmaceuticals with accuracy and reliability, and is

applicable to a wide range of fields, including R&D, marketing, quality control and quality

assurance.

Features

●　Evaluates not only five basic taste, but “richness” and “sharpness” which cannot be

evaluated by conventional analytical instruments.

●　Provides a maximum of 11 kind of taste information based on the types of taste

sensors used, without having to perform complicated multivariate analyses.

●　Offers the same taste quality and intensity for any sample as humans perceive.

●　One of the network systems to connect some instruments and allow some users to analyze

simultaneously.

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Specifications

SCHEMATIC ILLUSTRATION OF THE TS-5000Z

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SYSTEM ATTRIBUTES

Name Item Specifications

Instruments

Number of measurement samples

14 samples max. (depends on measurement procedure)

Measurement sample volume

35 to 70 ml (depends on the nature of measurement sample)

Weight 26 kg

Dimensions (W x D x H)

470 mm x 530 mm x 510 mm

CPU SH7727

OS (embedded)

SuperH Linux

Memory 64MB

Simple web server

Thttpd

Software

Instrument application:selection of measurement procedure, starting measurement, graphic of measurement results, etc.

Taste sensor

Response mechanism

Membrane potential measurement

Sensor type Artificial lipid-based membrane

Measurement object

Drinsk, solids, drugs, etc. (in case of solids, preliminary liquefaction is required.)

Ceramic reference electrode

Liquid junctionSingle junction through ceramic

Temperature sensor

Response mechanism

Impedance measurement using platinum resistance thermometer (Pt1000)

Management CPUHard disk

Pentium 4, 2.0 GHz or higher160 GB or more

server

Memory capacity

1 GB or more

Hard disk OS: 80BG, DB: 250GB

Memory 1GB

OS Linux

DBMS PostgreSQL

Web server Apache + Tomcat

Software

Management system:Creation of measurement procedure, sensorname and sample name, settings of users and their authority

Analysis application

Web browser required

Internet Explorer 6.0 or higher

Functions

Data search, data processing function, correction processing (5 types), statistical analysis, multiple regression analysis, principal component analysis, graphing tools (8 types), macro function, etc.

OS required Windows XP, Vista, WIN 7

Maintenance software

FunctionsData import, editing of ref files in the database, etc.

OS required Windows XP, Vista, WIN 7

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MECHANISM AND WORKING :-

The artificial taste sensors can be designed to mimic the mammalian taste sensors. The transducer

is replaced by lipid polymer membranes that act as taste buds or taste recepting organs. The human

brain is replaced by the computer which back propagates the signals or tastes received. The

algorithm used for data processing is based on artificial neural network, which functions according

to the learning and recognition pattern utilized by the human brain. It has been reported that a

multi channel taste sensor whose transducer is composed of several kinds of lipid/polymer

membranes with different characteristics can be used to detect taste. Taste information is

transformed into a pattern composed of electronic signals of the lipid membrane potentials. The

sensor measures taste quality since different substances produce different electric potential pattern.

The lipid/polymer membrane is a soft, transparent film of 200 μm thickness.

Lipids used for preparing the membrane includes oleic acid, oleyl amine, decyl alcohol.

Composition of lipids in the membrane depends upon the substance to be analyzed e.g. for amino

acids measurements, hybrid membranes composed of dioctyl hydrogen phosphate and methyl

trioctyl ammonium chloride are used. Commonly used polymers for preparing the membrane

includes polyvinyl chloride and dioctyl phenyl phosphate [5,6]. Each lipid/polymer membrane is

fitted on the part of a plastic tube, which has a hole, such that the inner part of the cylinder is

isolated from the outside. The end of the cylinder is sealed with a stopper that holds an Ag/AgCI

electrode. The tube is filled with 3 M KC1 solution. Eight detecting electrodes thus prepared

were separated to two groups, and connected to two electrode holders, which could be controlled

mechanically by a robotic arm.

The artificial taste sensor, other wise known as ‘Electronic Tongue’ has been used for the

estimation of food tastes by mimicking human gustatory system [6]. It consists of an array of

sensing elements, and a data processing unit as an alternative for the human tongue and the brain

respectively. The sensing element consists of an array of transducers that are sensor array

nonselective and non-specific like that of human taste buds.

21

The generates a pattern, which is in close proximity with the characteristics of the sample

analyzed

Above figure illustrates the interaction between chemical substances to produce taste and a

lipid/polymer membrane used in the taste sensor. Sodium ions producing saltiness make

electrostatic interaction with the membrane, while hydrogen ions producing sourness bind to the

hydrophilic part of the membrane.

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Umami taste substances such as MSG (Monosodium Glutamate) and IMP (Inosine Mono

Phosphate) interact with the membrane accompanied with weak binding. Sweet substances

accept protons from the membrane to result in the decrease in membrane potential. Bitter-tasting

substances such as quinine and L-tryptophan penetrate into the hydrophobic part of lipid

membrane to increase the membrane potential. In this way, the chemical nanostructures of taste

substances are recognized by the lipid membrane by different mechanisms. The response electric

potential is different for chemical substances showing different taste qualities in each membrane

and, furthermore, is different in other membranes.

Equipment

The electronic tongue consists typically of four working electrodes made of the metals gold,

iridium, platinum and rhodium, an Ag/AgCl reference electrode and a stainless steel counter

electrode. A relay box is used, enabling the working electrodes to be connected consecutively to

form four standard three-electrode configurations. The potential pulses/steps are applied by a

potentiostat which is controlled by a PC. The PC is used to set and control the pulses, measure and

store current responses and to operate the relay box. The detail illustration is given below:-

Working Electrode

The working electrode is an innert material such as Gold, Platinum, Glassy Carbon, iridium

and rhodium etc. In these cases, the working electrode serves as a surface on which the

electrochemical takes place. It places where redox reaction occur. Surface area should very

less (few mm2) to limit current flow

Reference Electrode

An Ag/ AgCl reference electrode is used in measuring the working electrode potential. A

reference electrode should have a constant electrochemical potential as long as no current

flows through it.

Auxillary electrode

A stainless steel counter electrode is a conductor that completes the cell circuit. It is generally

inert conductor. The current flow into the solution via the working electrode leaves the solution

via the counter electrode. It does not role in the redox reaction.

23

A relay box is used, enabling the working electrodes to be connected consecutively to form four

standard threeelectrode configurations. The potential pulses/steps are applied by a potentiostat

which is controlled by a PC. The PC is used to set and control the pulses, measure and store

current responses and to operate the relay box. The set-up is illustrated in Figure.

Measurement principle and data analysis

In voltammetric measurements a current is measured between the metal working electrode and

the counter-electrode when a voltage pulse is applied over the working electrode and the

reference electrode. A set of pulses can be put together to form a pulse train in order to extract as

much information as possible from the solution. When the potential is applied, electro-active

compounds that react to that potential will be reduced or oxidized and a current, that can be

measured, will arise.

In measurements with the voltammetric electronic tongue, data are collected over the whole

pulse and not only at the end of the pulse, as in traditional electrochemistry. This is done since it

has been found that extra information is also found at the beginning of the pulse (mainly

conductivity and mobility).

The electronic tongue creates a data matrix that is treated with MVDA, e.g. principal component

analysis (PCA). PCA explains the variance in the experimental data and reduces the large data

set to plots that can be easily surveyed. PCA produces a ‘score plot’ that visualizes differences

between the experiments. This can be used for classification or grouping of the experiments.

24

ADVANTAGES OF ELECTRONIC TONGUE

1) The electronic tongue or taste sensor has the ability to pick the slightest change in chemical

concentration where human tongues cannot.

2) It’s ability to be objective, precise, reproducibility, and consistent make it a valuable tool to

our society.

3) They may help in reducing water pollution and decrease in the rate of water borne diseases

4) It can also be used for the analysis and quantification of blood electrolytes proving to be

much more efficient then older techniques

5) It can be used in bio medical purpose and can find a numerous use in that sector.

6) It can also be used in detecting alcoholic.

7) It can be used in pharmaceutical sector for detecting the bitterness and effectiveness of the

medicine.

8) It can be used to detect toxicity of a particular liquid.

DISADVANTAGES OF ELECTRONIC TONGUE

1. No sensors for some of the analytes.

2. Not precise in all the cases.

3. Sometimes insufficient selectivity.

4. Not portable from one place to another.

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APPLICATION OF ELECTRONIC TONGUE IN DIFFERENT FIELD

General Application

I) As a qualitative tool for checking hardness of water

Environmental pollution has diminished drinking water quality. Hence drinking water quality

evaluation has become critical these days. Taste of mineral water is quite subtle and hence it is

difficult for humans to discriminate between different brands of water. Hence taste sensors

responds well to different kinds of mineral water. Even very low concentrations of taste substances

can be easily discriminated between different brands of mineral water because of high sensitivity

of taste sensors to ions. Koseki et al. researched the pH dependence of the taste of alkaline

electrolyzed water (AEW) made by electrolyzing bottled mineral waters by sensory evaluation

using biomimetic sensors and concluded that electrolysis probably improved the taste of water

with a higher calcium concentration by reducing the calcium concentration; however, the effect of

electrolysis on water with a calcium concentration of 10 mg/L is likely to be the result of the pH

increase alone. The taste sensors are capable to distinguish between different types of mineral

waters based on their high sensitivity to ions.

II) Effluent water analysis

Toxic substances in factory drains could be easily analyzed with taste sensors. Many pollutants

such as CN¯ , Fe3+, Cu2+ could be measured in a few minutes with the detection limits lower than

regulations of drain. Nistor et al. evaluated the potential use of biosensors, not as quantitative tools

for phenol analysis, but rather as screening tools indicating a certain trend, i.e. compounds present

or not present, and potential correlation with sample toxicity and also studied the effect of several

potentially interfering compounds on the sensor response.

III) Measurement of smell

Taste substances differ from odor substances in that they have low molecular weight and low

volatility. Odorous ingredients can be extracted and concentrated from food samples bydistillation

using evaporator. Therefore “flavored water” can be prepared using these odorous extracts. Smell

of food samples can be evaluated by subjecting flavored water to testing with the help of taste

sensors. Kataoka etc.

26

Experimented on bottled nutritive drinks and found a positive linear correlation between the

intensities of sourness and bitterness determined by the human volunteers and those predicted by

the taste sensor. The pungency intensity, as evidenced in gustatory sensation tests, was also

predicted by sensor output and taste sensor seems therefore to be a potentially useful tool in

evaluating the palatability of bottled nutritive drinks.

IV) Qualification of the beverages and food items

Taste sensors can be used as comprehensive tool for maintaining the quality of liquid beverages

like beer thereby avoiding batch-to-batch variation in the taste of the beverages. While the sensors

could be applied to beverages, it can also be used for analysis of the taste of gelatini form or solid

foods. When eating food, humans first masticate the food with their teeth and then taste it.

Therefore, a mixer can be used in place of teeth for crushing the food item (whose taste is to be

evaluated) before measuring their quality using taste sensors. Thus taste of food items could be

easily qualified with sensitivity and selectivity with the help of taste sensors. Moreover, these

sensors can be used effectively as a quality control tool for discriminating between fresh and

spoiled milk and to follow the deterioration of milk quality when it is stored at different

temperatures or storage conditions. Umami taste intensity of green tea has been graded

meticulously by taste sensors. Sensory analyzed results showed high degree of correlation to the

human gustatory sense.

Pharmaceutical Application

I) Selection and optimization of appropriate taste masking agents / methods

Various taste masking agents could be screened for the effectiveness using taste sensors. Once

appropriate taste masking agent has been identified, next step would be quantification of the

masking agent. High sensitivity and selectivity of taste sensors is helpful for optimization of the

concentration of the masking agent. However it has been found less useful in comparative studies

between complex liquid formulations. Usually, a liquid formulation includes large portion of

sugars and other sweeteners with small portion of taste enhancers, flavors and viscosity

modulators. However optimization of a liquid formulation is mainly focused on taste enhancers

and flavors while assessment of liquid formulations by taste sensors, electronic signals are

dominated by a large amount of sugars and sweetness and flavors may not be detected .

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These techniques may also be employed for the development of novel pharmaceutical taste

masking technologies that can be conclusively optimized by taste sensors. Furthermore, these

sensors could be used to evaluate the taste-masking and sustained-release characteristics of

pharmaceutical formulations.

Hashimoto et al. worked on quantitative prediction of the bitterness-suppressing effect of

sweeteners (sucrose or sugar alcohols) on the bitterness of famotidine (or quinine sulfate as

control) solutions using an artificial taste sensor and concluded that the sugar alcohols in the tablet

seem to be effective in the bitterness-suppression of famotidine from these tablets, especially in the

initial phase (within 30 s) of the disintegration process.

Kayumba et al. evaluated quinine sulphate pellets for flexible pediatric drug dosing using

electronic tongue. Eudragit EPO was used for coating quinine sulphate pellets. Selection of the

optimal formulation among pellets having different coating thickness was made by electronic

tongue that evaluated bitterness intensity in function of time.

II) Qualitative evaluation of bitterness of APIs

Taste sensors could also be utilized for the qualitative analysis of bitter compounds. Moreover

artificial taste sensors could be used for quantitative bitterness prediction and comparative

bitterness examination of bitter APIs . Zheng and Keeney found that for a group of compounds, the

group distance between a compound and water may indicate the degree of bitterness or taste. A

larger distance between water and a compound may imply stronger taste or bitterness of the

compound. Thus a relative rank order of bitterness could be obtained based on the distance data,

which may further be a result of the taste sensing and technology. Prednisolone and quinine are

found to be very bitter while caffeine and sucrose octaacetate (food additive) are less bitter. Based

on group distance, the relative ranking of bitterness of these compounds would be in the following

order: Ranitidine HCl > Prednisolone Na > Quinine HCl ~ Phenyl thiourea > Paracetamol >

Sucrose octaacetate > Caffeine.

Kataoka et al. investigated the use of the artificial taste sensor in the evaluation of some medicinal

plants and chinese medicines with bitter and/or astringent tastes, and assessed the possible

application of the sensor in the evaluation of taste and quality control of medicinal products. Else

more, the berberine content in extracts of medicinal plants was evaluated by the taste sensor, and it

was shown to be possible to use the taste sensor for the quality control of medicinal plants

CONCLUSION

Taste sensors can provide a technically suitable and cost effective method for screening and

analyzing taste in the early stages of the development of API/formulations, thereby eliminating

both safety concerns and subject bias effects. In conclusion, taste sensors may be useful in

evaluating taste masking efficiency for a formulation, development of a matching placebo and

for ranking the taste/bitterness of new chemical substances. Miniature sensor chips could be

possible futuristic approaches for the development of widely applicable taste sensor technology

in this new generation of the IT world. This is high-level function, where intelligent sensing is

required. In this meaning, the taste sensor is essentially an intelligent sensor to reproduce the

taste sense, which is a complex, comprehensive sense of humans. The electronic tongue can

differentiate between tastes, but in a very few cases it ranked masking agents in a different order

than that determined by human volunteers.

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REFERENCE

1. http://www.wikipedia.com

2. http://www.edutalks.com

3. http://www.ieee.org

4. http://google.com

5. http://freeebooks.com

6. MulticbamA Taste Sensor Using Lipid Membranes

K Hayashi, M Yamanaka, K Toko, K Yamafuji in Sensors And Actuators (1990)

7. Sensor fusion for taste sensor and odor sensor.

T Katsube, S Umetani, Liqin Shi, Y Hasegawa in Chemical Senses (2005)

8. Detection of suppression of bitterness by sweet substance using a multichannel taste

sensor.

S Takagi, K Toko, K Wada, H Yamada, K Toyoshima in Journal of Pharmaceutical

Sciences (1998)

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