When sensors that detect the five senses, hearing, sight, feeling, smell, and taste, are discussed, the one that usually gets mentioned the least is taste. Electronic ears, eyes, touch, and noses have far more available products than electronic tongues – but that could change. Like many sensors, the underlying technology for an electronic tongue (or E-tongue) can differ widely.
Metal-oxide-semiconductor field-effect transistor (MOSFET) technology, commonly used for logic (complementary metal-oxide-semiconductor or CMOS) devices and power switching with a source, drain and gate, is also used for biosensors. In an ion-sensitive field-effect transistor or ISFET (one of first biosensors), the metal gate is replaced by an ion-sensitive membrane, with an electrolyte solution and a reference electrode. Chemical field-effect transistors (ChemFETs) are derivatives of ISFETs. In both instances, these potentiometric sensors have a predictable response function based on fundamental relationships and measurable parameters.
For taste sensing by an E-tongue, the five primary or basic taste qualities are sweet, sour, salty, bitter, and umami (savory).
Existing products for E-tongue sensors
Available products with E-tongue capabilities are primarily analytic instruments in research laboratories.
For example, one company provides taste analysis using an electronic tongue so users’ products can be evaluated more easily by characterizing their taste in the development phase. Using their instrumentation, customers can avoid possible health hazards that can occur when a panel of testers evaluate products containing harmful or unpleasant molecules.
The electronic tongue evaluates the taste of products based on ChemFET liquid sensor technology and conductivity measurement. With its autosampler capability that allows automation of an analysis sequence, samples can be analyzed every 3 minutes.
Another company’s Taste Sensor System has a taste sensor based on biomimetic technology inspired by nature to create biological membranes. The company’s patented lipid/polymer membrane generates a voltage that varies according to its interaction with a specific taste attribute. Membrane response characteristics are adjusted by changing the types of membrane lipids (a structural component of a membrane that provides signaling molecules), plasticizing agents, and the varied ratio of multiple lipid types with selective responses to specific tastes. The proprietary lipid and polymer membranes mimic living organisms.
The sensor can evaluate and correlate with intensity the five basic tastes and astringency (dryness, tightening, and shrinking) with capabilities equivalent to or better than human taste sensitivity. Its response covers the human dynamic range (from 1 to 10 times the threshold).
To overcome the subjectivity in traditional flavor evaluation in food testing, another company’s E-tongue technology targets a more objective, thorough, and repeatable analysis of a food product’s flavor profile than other methods. Their technology converts molecular taste information into visual data that can be easily analyzed using mathematical optimization techniques.
Their e-tongue accurately characterizes taste differences across eight key categories:
- Bitterness
- Bitterness Aftertaste
- Astringency
- Astringency Aftertaste
- Umami
- Richness
- Sourness
- Saltiness
The E-tongue test offers a tool for product benchmarking and understanding consumer taste perceptions with repeatability that surpasses traditional human taste panels and physical testing methods. The company successfully used its e-tongue testing on a wide range of food products, including beverages, ingredients, solids, and packaging materials.
Part 2 will discuss some recent efforts in E-tongue development.
References
Piet Bergveld-40 years of ISFET technology: From neuronal sensing to DNA sequencing
ASTREE, taste sensors electronic tongue
e-Tongue, Insent Taste Sensing System, TS-5000Z
What is E-Tongue Testing and How Can It Benefit Your Food Product?
Filed Under: Sensor Tips, Medical-device manufacture