In all industries, odor assessment is usually performed by human sensory analysis, by chemosensors, or by gas chromatography. The latter technique gives information about volatile organic compounds but the correlation between analytical results and mean odor perception is not direct due to potential interactions between several odorous components.
In the Wasp Hound odor detector, the mechanical element is a video camera and the biological element is five parasitic wasps who have been conditioned to swarm in response to the presence of a specific chemical.

A typical issue with odor detection is that it measures physical particles rather than energy. Essentially, the device comprises of head space sampling, a chemical sensor array, and pattern recognition modules that create signal patterns used to characterize scents. Electronic noses have three primary components: a sample delivery system, a detecting system, and a computation system.

• The sample delivery system: allows for the creation of a sample’s headspace (volatile compounds), which is then examined. The system then injects the headspace into the electronic nose’s sensing system. The sample delivery system is vital for maintaining constant operational conditions.
• The detecting system: which includes a sensor set, is the instrument’s “reactive” component. When in touch with volatile compounds, the sensors respond, resulting in a change in electrical characteristics. In recent years, different types of electronic noses have been created that use mass spectrometry or ultra-fast gas chromatography as a detector.
• In most electronic noses, each sensor is sensitive to all volatile molecules, but in their own unique way. However, in bio-electronic noses, receptor proteins that respond to particular odor molecules are utilized. Most electronic noses employ chemical sensor arrays that react to volatile compounds upon contact: the adsorption of volatile compounds on the sensor surface leads to a physical change to the sensor. The electrical interface records a specific response, converting the signal into a digital value. The recorded data is subsequently calculated using statistical models.
• The computer system: combines the reactions of all sensors, which serve as input for data processing. It gives findings and representations that are easy to understand. Furthermore, electronic nose data can be compared to those acquired using other techniques (sensory panel, GC, GC/MS). Many data interpretation systems are utilized for the examination of outcomes. These systems include artificial neural networks (ANN), fuzzy logic, chemometrics, pattern recognition modules, and so on. Artificial intelligence, including artificial neural networks (ANNs), is an important technology for environmental odor management.

Electronic Nose

Electronic noses often employ metal-oxide-semiconductor (MOS) sensors, which have an electrical resistance that varies in response to a target gas. The presence of the target gas can be determined by measuring the change in resistance of the metal oxide layer over time.
Conducting polymers are organic polymers that conduct electricity.
Polymer composites, which are used in the same way as conducting polymers but are made up of non-conducting polymers with the addition of a conducting substance like carbon black.
Quartz crystal microbalance (QCM) is a method of determining mass per unit area by monitoring the frequency shift of a quartz crystal resonator. This can be saved in a database for future reference.

Surface acoustic wave (SAW) is a type of microelectromechanical system (MEMS) that detects physical phenomena by modulating surface acoustic waves.
Mass spectrometers can be miniaturized to provide a general-purpose gas analysis instrument.
Some devices, such as polymer-coated QCMs, integrate numerous sensor types. Independent information results in far more sensitive and efficient devices.

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Performing an analysis

As an initial step, an electronic nose must be trained on certified samples in order to develop a reference database. The equipment will recognize new samples by comparing a volatile compound’s fingerprint to those stored in its database. As a result, they can do both qualitative and quantitative analyses. However, it may cause problems because many odors are composed of numerous distinct molecules, which the device could interpret as various compounds, leading in invalid or inaccurate findings depending on the nose’s primary function.

Applications

• In quality control laboratories: This involves ensuring the consistency of raw materials, intermediate and final products, detecting contamination, spoilage, and adulteration, selecting origin or vendors, monitoring storage conditions, and monitoring meat quality.
• In the process and production departments: This involves managing raw material variability, comparing with a reference product, measuring manufacturing process effects on products, enhancing cleaning efficiency, and monitoring scale-up and cleaning in place.
• In product development phases: This involves sensory profiling, comparing different formulations or recipes, benchmarking competitive products, and evaluating the impact of process or ingredient changes on sensory features.
• Possible and future applications in the fields of health and security: Software developed to detect harmful bacteria, such as MRSA and MSSA, can prevent contamination in hospital ventilation systems. It can also detect lung cancer, medical conditions, COPD exacerbations, food quality control, and natural gas presence. Nasal implants can alert those with anosmia or a weak sense of smell. The Brain Mapping Foundation uses electronic noses to detect brain cancer cells.
• Possible and future applications in the field of crime prevention and security: Electronic noses can detect odorless smells, making them useful in police forces and airports for drug detection. They can triangulate drug locations within a few meters, while demonstration systems detect explosive vapors but are still behind trained sniffer dogs.
• In environmental monitoring: This document aims to identify volatile organic compounds in air, water, and soil samples for environmental protection.