E nose in food industry

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2. TNAU- Tamil Nadu Agricultural University
Department of Food and Agrl. Process Engineering
Seminar on
“ELECTRONIC NOSE (E-nose)”
Presented by:
Nisha. R
Ph.D Scholar
2016804101
2
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3. Electronic noses are engineered to mimic the
mammalian olfactory system.
Instrument designed to allow repeatable identifications
and classifications of aroma mixtures.
Determines the various characteristics properties of the
odour while eliminating operator fatigue.
Hundreds of different prototypes of artificial-nose
devices have been developed to discriminate complex
vapor mixtures containing many different types of volatile
organic compounds (VOCs)
e-sensing
Refers to the capability of reproducing human senses
using sensor arrays and pattern recognition systems.
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4. An electronic nose is an array of non-specific chemical
sensors, controlled and analyzed electronically, which
mimics the action of the mammalian nose by recognizing
patterns of response to vapors.
The sensors will conduct chemical sensors which
change resistance when exposed to vapors, and are not
specific to any one vapor it is in the use of an array of
sensors, each with a different sensing medium.
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5. Of all the five senses, olfaction uses the largest part
of the brain and is an essential part of our daily lives.
Quantifying smells are useful in gas
chromatography
Human nose is very sensitive.
Subject to fatigue, inconsistencies, adaptation etc.
Smelling toxic gases may involve risk
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6. Bio-nose Electronic nose
It uses the lungs to bring the odor
to epithelium layer
It employs a pump to smell the odor
It has mucus, membrane, and hair to
act as filter
It has an inlet sampling system that
provides filtration
The human nose contains the olfactory
epithelium, which contains millions of
Sensing cells that interact with
odorants in unique
Electronic nose has a variety of sensors
that interact differently with a group of
odorous molecules
Convert the chemical response to
electronic nerve impulses whose
unique patterns are propagated by
neurons.
Electronic nose react with the sample
and produce electrical signals.
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Human oflaction
Olfactory
receptors
Olfactory bulb Brain
E nose Sensory array Signal transducer
Pattern recognition
system
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8. Sample handling system
Sensing system
Data acquisition system
Signal processing & pattern
recognition
sample injection stage
Result recorder6/21/2017 8Nisha. R

9. Eliminates all undesirable factors that could affect sensor response
and ensures a stable and repeatable headspace of gas sampling
environment.
Temperature and humidity are constantly monitored both in the
sample chamber and in the sensor chamber, while the analysis is
running.
After headspace sampling, ambient air is applied to both chambers
to prevent potential contamination (residue from previous sample
and environment).
The sample chamber must be made from non-adsorbing and inert
materials.
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10. It is comprised by a group of several sensors measuring
different flavor properties with various selectivity or by
a single detecting device (e.g., a mass spectrometer)
carrying out a series of measurements of a given aroma
profile, or a combination of these two types.
The type and number of sensors play a key role in
determining the applicability of the e-nose instrument.
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11. The signal is processed, and a distinguishing feature of
this system is the recording method of the sensor
response signal.
Some aromas change their profiles over time,
depending on whether they are static or dynamic.
A data series formed by averaging signals from a
sensor is more suitable.
It can provide more information on aromas and an
identification process for flavors is more simple and
reliable.
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12. It identifies the odour profile by comparison with known
profiles from the database.
It associates each pattern to one of many possible reference
classes. Odors are characterized on the basis of greater or
lesser similarity of given features and they are assigned to a
given class.
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Primed by passing a reference gas or pure dry air through
the sample and sensor chambers.
Removes residues and impurities remaining from a
previously analyzed sample
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Rmin is the
baseline resistance
Rmax the
resistance in the
odor
I – flow of
reference gas
II – measuring
sample headspace
III –recovery step
Arshak, et.al, 2004
Fig. 4. : Characteristic of the response of e-nose
sensor to an odorant.
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The sensor array is clearly the key element. It forms the
primary step in the detection or identification of an
odorant.
The sensors on an electronic nose system should be
selectively sensitive to odors which may be present in a
given kind of tested sample.
The most commonly used sensors in electronic nose are:
sensors
Metal oxide
sensors
(MOS)
Conducting
polymers
Optical
sensors
Piezoelectric
sensors
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15. Metal oxide sensors (MOS)
Commonly and most utilized sensor systems for the
development of electronic noses to detect gaseous
molecules.
Major principle: adsorption or desorption of gaseous
molecules on the surface of a metal oxide changes the
conductivity of material.
When oxides are exposed to volatile organic compounds
(VOCs), they are involved in a redox reaction on the
surface of the MOS or act as oxidizing agents and, thereby,
cause a shift in the resistance of the MOS
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Conducting polymer sensors
Here the active material is a conducting polymer from
such families as the Polypyrroles, thiophenes, indoles
or furans.
CP sensor arrays often consist of unique polymers with
different reversible physicochemical properties and
sensitivity to groups of volatile.
These organic vapors attach to and interact with the
polymer surface, changing the resistance under
ambient temperature conditions

17. All of the polymer films on a set of electrodes (sensors) start out
at a measured resistance, their baseline resistance. If there has
been no change in the composition of the air, the films stay at the
baseline resistance and the percent change is zero.
e- e- e- e- e- e-
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18. Each polymer changes its size, and therefore its resistance, by a different
amount, making a pattern of the change
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If a different compound had caused the polymer to change, the
pattern of the polymer films' change would have been different.

19. PIEZOELECTRIC SENSORS
A piezoelectric sensor is a device that uses the
piezoelectric effect to measure any physical change
like pressure, strain etc. Here,the gas adsorption leads
to change in mass of the sensor .
Quartz crystal microbalance (QCM) and surface
acoustic wave (SAW) sensors are two of the most
useful piezoelectric sensors applied in electronic noses.
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20. OPTICAL SENSORS
These utilize glass fibers with a chemically active
material coating on their sides or ends.
A light source is used to interrogate the active
material which responds with the change in color
to the presence of VOCs.
The active material contains chemically active
fluorescent dyes. As the VOCs interact with it, the
color of the fluorescent dye changes, hence lead to
detection.
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21. FEW SENSORS
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22.  The Cyranose 320 is a
handheld “electronic
nose” developed by
Cyrano Sciences of
Pasadena, California in
2000.
 Applications researched
using the Cyranose 320
includes the detection of
COPD, and other medical
conditions as well as
industrial applications
generally related to
quality control or
contamination detection.
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23. Nisha. R 23
Industry
sector
Application area Specific use types and
examples
Agriculture crop protection
harvest timing & storage
meat, seafood, & fish
products
plant production
pre- & post-harvest
diseases
safe food supply, crop ripeness,
preservation treatments, freshness,
contamination, spoilage, cultivar
selection, variety characteristics,
plant disease diagnoses, pest
identification
Environmental air & water quality
monitoring, indoor air
quality control
pollution detection, effluents, toxic
spills, toxic/hazardous gases
Food & beverage quality control
assessments, ripeness, food
contamination, taste, smell
characteristics
ingredient confirmation, content
standards, marketable condition,
spoilage, shelf life
Manufacturing processing controls,
product uniformity, safety,
security, work conditions
product characteristics &
consistency, aroma and flavor
characteristics, fire alarms, toxic
gas leak detection
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26. Kriengkri et al ., 2016
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Evaluation of bacterial population on chicken
meats using a briefcase electronic nose
Objectives
Performance of novel portable electronic nose (E-nose)
based on eight metal oxide sensors was used for
evaluation of chicken meat freshness and bacterial
population on chicken meat stored at 4.0 C and 30.0 C
for up to 5 days

27. Sliced chicken breast meat samples were obtained from a
local market.
The samples were then cut into pieces of the same weight
(10 g ± 1 g) and stored under different temperatures (4.0o
C and 30.0o C) for 5 days in temperature controller
incubators.
These storage temperatures were selected to mimic the
sample storage in a refrigeration system (4.0o C) and room
temperature (30.0o C).
Chicken freshness evaluation was performed everyday by
using E-nose measurement.
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28. Fig. 1: Briefcase E-nose.
The portable E-nose system, called
briefcase Enose consists of four
parts
(I) valves and air
pump with mass flow controller
(II) sampling system
(III)sensor array and
(IV) data acquisition (DAQ) with a
computer
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29. List of gas sensors with sensing types and
detection ranges.
Sensor name Sensing type Typical detection
ranges (ppm)
TGS 821 Hydrogen 10-10,000
TGS 822 Organic solvent vapours 50-5000
TGS 825 Hydrogen sulfide 5-100
TGS 826 Ammonia & alcohols 30-300
TGS 2600 Air contaminants 1-100
TGS 2602 VOCs and odorous gases 1-30
TGS 2610 LP gas 300-10,000
TGS 2620 Solvent vapours 50-5000
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30. Fig. 2: Schematic diagram of the briefcase E-nose.
(Timsorn et.al, 2016)
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31. The changing of sensor
resistance results from the
adsorption/ desorption
reactions between the
volatile organic
compounds (VOCs) from
sliced chicken breast and
the adsorbed oxygen ion
(O) on the crystal surface
of MOS.
Fig. 3: A signal of the sensor recorded as
resistance values versus time.
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Fig. 6: Three dimension plots of average sensor responses to sample
odours when samples were stored (a) 30.0o C and (b) 4.0o C for three
and five storage days, respectively.

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PCA score plot for discrimination of chicken sample
freshness.Nisha. R

34. A portable E-nose based on eight MOS sensors with specially
designed system and sensor chamber has been successfully
constructed and used for identification of chicken breast freshness.
The E-nose exhibits fast response to chicken breast odours within
20e30 s. Storage temperature strongly affects the rate of spoilage
bacterial development in chicken meat.
Most VOCs emitted from chicken breast malodour are reducing
gases.
With PCA analysis, the E-nose can well classify the chicken breast
odours corresponding to different storage days (0-5 days) and
temperatures.
It is a portable, rapid, low cost, nondestructive technique, which can
achieve high accuracy and can be used without environmental
controls (no need for nitrogen or air zero as a carrier gas)..0 C and
4.0 C).
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35. E-nose to trace tomato-juice quality
XuezhenHonget.al,2015
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36. E-nose and sampling procedure.
Each sample (10 mL of cherry tomato juice) was placed
in a 500 mL airtight glass vial that was sealed with
plastic wrap for 10 min.
The headspace gaseous compounds were pumped into
the sensor arrays through Teflon tubing connected to a
needle in the plastic wrap, causing the ratio of
onductance G/GO
(G and G0 are conductance of the sensors exposed to sample gas
and zero gas, respectively)
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Fig. 1. Typical e-nose responses to juices squeezed from
youbei cherry tomatoes stored for (a) 7 and (b) 8 days.Nisha. R

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Changes of ten e-nose sensors towards storage time
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Fig. 3. Visualization of underlying data structure of juices squeezed
from tomatoes with different storage time by PCA.
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This work successfully employed an e-nose combined with
chemometrics to trace quality indices (storage time, pH,
SSC, VC and firmness) of cherry tomatoes that were
squeezed for juice consumption. The proposed semi-
supervised classifier – Cluster-then- Label based on
spectral clustering and majority voting – was found more
reliable and robust than the supervised approaches, and it
outperformed the four supervised approaches

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