Electronic tongue

Electronic Tongue working principle
The electronic tongue is an instrument that measures and compares tastes. ,

Chemical compounds responsible for taste are perceived by human taste receptors, and the seven sensors of electronic instruments detect the same dissolved organic and inorganic compounds. Like human receptors, each sensor has a spectrum of reactions different from the other. The information given by each sensor is complementary and the combination of all sensors results generates a unique fingerprint. Most of the detection thresholds of sensors are similar or better than those of human receptors.

In the biological mechanism, taste signals are transducted by nerves in the brain into electric signals. E-tongue sensors process is similar: they generate electric signals as potentiometric variations.

Taste quality perception and recognition is based on building or recognition of activated sensory nerve patterns by the brain and on the taste fingerprint of the product. This step is achieved by the e-tongue’s statistical software which interprets the sensor data into taste patterns.

How to perform an analysis with the E-Tongue
Liquid samples are directly analyzed without any preparation, whereas solids require a preliminary dissolution before measurement. Reference electrode and sensors are dipped in a beaker containing a test solution for 120 seconds. A potentiometric difference between each sensor and a reference electrode is measured and recorded by the E-Tongue software. These data represent the input for mathematical treatment that will deliver results.

Range of applications
Electronic Tongues have several applications in various industrial areas: the pharmaceutical industry, food and beverage sector, etc. It can be used to:
 * analyze flavor ageing in beverages (for instance fruit juice, alcoholic or non alcoholic drinks, flavored milks…)
 * quantify bitterness or “spicy level” of drinks or dissolved compounds (e.g. bitterness measurement and prediction of teas)
 * quantify taste masking efficiency of formulations (tablets, syrups, powders, capsules, lozenges…)
 * analyze medicines stability in terms of taste
 * benchmark target products.

Artificial Taste
The electronic tongue uses taste sensors to receive information from chemicals on the tongue and send it to a pattern recognition system. The result is the detection of the tastes that compose the human palate. The types of taste that is generated is divided into five categories sourness, saltiness, bitterness, sweetness, and umami (deliciousness). Sourness, which includes HCl, acetic acid, and citric acid is created by hydrogen ions (Zheng and Keeney 2006 pg 118). Saltiness is registered as NaCl, sweetness by sugars, bitterness, which includes chemicals such as quinine and caffeine is detected through MgCl(2), and umami by monosodium glumate from seaweed, disodium in meat/fish/mushrooms (Zheng and Keeney 2006 pg 118). For more detail see www.cyborgdb.org.

Resources: Zheng, JY, & Keeney, MP. (2006). Taste masking analysis in pharmaceutical formulation development using an electronic tongue. International Journal of Pharmaceutics, 310(1-2), 118-24.