ENOSE Flashcards
E-NOSE
• An instrument, which comprises an array of electronic chemical sensors and an appropriate pattern recognition system, is capable of recognizing simple or complex odor or smell
• Electronic noses (e-noses) are devices used for analysing food aroma generally without separation and identification of volatile compounds.
A typical e-nose comprises :
(1) the sampling system
(2) a set of non-selective sensors or a mass spectrometer (MS), or their combination as a collecting unit
(3) a data acquisition system
How does e-nose work?
• The electronic nose was developed in order to mimic human olfaction that functions as a non-separative mechanism: i.e., an odor / flavor is perceived as a
global fingerprint.
• Essentially, the instrument consists of head space sampling, a chemical sensor array, and pattern recognition modules to generate signal patterns that are used for characterizing odors.
Electronic noses include three major parts
1) A sample delivery system
2) A detection system
3) A computing system
Sample delivery system
1) Enables the generation of the headspace (volatile compounds) of a sample, which is the fraction analyzed.
2) The system then injects this headspace into the detection system of the electronic nose.
3) The sample delivery system is essential to guarantee constant operating conditions.
Detection system
1) consists of a sensor set, which is the “reactive” part of the
instrument.
2) When in contact with volatile compounds, the sensors react, which means they experience a change of electrical properties
3) In most electronic noses, each sensor is sensitive to all volatile molecules, but each in their specific way.
4) Most electronic noses use chemical sensor arrays that react to volatile compounds on contact: the adsorption of volatile compounds on the sensor surface causes a
physical change of the sensor.
Computing System
• The computing system works to combine the responses of all of the sensors, which represents the input for the data treatment.
• This part of the instrument performs global fingerprint analysis and provides results and representations that can be easily interpreted.
• Moreover, the electronic nose results can be correlated to those obtained from other techniques (sensory panel, GC, GC/MS).
• Many of the data interpretation systems are used for the analysis of results.
• These systems include artificial neural network (ANN), fuzzy logic, chemometrics methods, pattern recognition modules, etc.
The more commonly used sensors for electronic noses include:
I) metal–oxide–semiconductor
II) conducting polymers
III) polymer composites
IV) quartz crystal microbalance (QCM)
V) surface acoustic wave (SAW)
VI) Mass spectrometers
Sensor Array
1) These sensors are designed to interact with volatile compounds present in the sample.
2) Each sensor responds differently to different odor molecules based on factors such as chemical reactivity,
surface morphology, and electrical properties.
3) The collective response of the sensor array provides a unique pattern or fingerprint for each odor.
Signal Processing Unit:
1) The signal processing unit receives the signals from the sensor array and processes them to extract meaningful information.
2) This unit may include analog-to-digital converters
(ADCs), amplifiers, filters, and digital signal processing (DSP) algorithms.
3) Signal processing algorithms analyze the sensor responses, normalize the data, and extract features that are characteristic of specific odors.
4) Machine learning techniques can also be employed to improve pattern recognition and classification
accuracy.
Pattern Recognition System
1) The pattern recognition system interprets the processed data to identify and classify different odors.
2) It compares the extracted features from the sensor responses against a database of known odor patterns or employs statistical methods to classify unknown odors.
3) This system may utilize pattern recognition algorithms such as artificial neural networks (ANNs), support vector
machines (SVMs), or principal component analysis (PCA) to recognize odor patterns and make accurate
Data Interface
1) The data interface allows for communication between e-nose and external devices such as computers or display units.
2) It enables users to visualize the results, store data for
further analysis, and control the operation of the e-nose.
3) This interface may include serial or USB ports,
wireless communication protocols (e.g., Bluetooth or Wi-Fi), or dedicated software applications for data management and visualization
E-noses can be utilized for Halal applications
- Detection of Non-Halal Ingredients:
•Alcohol and pork - Quality Control and Assurance:
•Flavor Profiling:
•Contamination Prevention - Supply Chain Verification:
• Ingredient Authentication - Meat Authentication:
• Species Identification - Detection of Spoilage and Freshness:
• Monitoring Freshness - Regulatory Compliance:
• Standards Adherence
Electronic nose method
• Ten grams of each oil sample were weighed into a septa-sealed screw-cap bottle.
• After a headspace generation time of 3 min at 60° C (in a water bath), the sample vapor was introduced into the electronic nose.
• Each sample was measured in triplicate, followed by blanks and n-alkane runs, to ensure quality of measurement.
• The flow rate of purified helium was fixed at 30.0 (mL/min), sampling time of 5 s, and temperature programmed from 40 to 160° C, at a rate of 5 °C/s.
Electronic nose analysis
• The chromatogram from the electronic nose is a graphical display of the derivative of the frequency change versus time.
• The peak area was correlated with the compound concentration and was expressed in counts (cts).
• A unique approach of the electronic nose was to use two-dimensional olfactory images, called VaporPrint.
• It is produced by a polar plot of the zNose chromatogram, using retention time as the angular variable and the SAW detector response as the radial variable.
• VaporPrint provides a high resolution image, which translates the olfactory response to a visual response.
