What is an OTV?
The Odour Threshold Value (OTV) of a compound (Aroma compound, Chemical or natural ingredient, Base or Composition…) is the level on which it can be detected by the human sense of smell. It is also called Detection Threshold.
History of OTV?
The measurement of odour thresholds goes back a long time.
The first OTV value was published by Zwaardemaker in 1895. In the 20th century, many researchers published OTV’s. A very complete compilation of values was prepared by Van Gemert.
From this compilation we can see that the values vary over a wide range, depending on the method used, the panel considered and the test conditions. In the 1980’s a radical change in the definition of the OTV happened in the NVN2820 standard method for olfactometry.
It aimed to make olfactometry more reproducible for application in the environmental sector and defined the Dutch odour unit as equivalent to the olfactory stimulus of 20 ppb/v of n-butanol in neutral odourless gas. In the subsequent European standard EN13725:2003 this approach was adopted but with a different agreed reference value.
The reference for the European odour unit was defined as the European Reference Odour Mass (EROM):
- One EROM is equivalent to 123 mg n butanol evaporated in 1 m3 of neutral gas this produces a concentration of 0,040 mmol/mol. In the revision of the EN13725, ongoing, a procedure for measuring the SROM for substances other than n-butanol was included.
- This new methodology therefore now makes it possible to clearly define the unit of measurement, the panel considered, and the study conditions to be respected to obtain a reliable and reproducible OTV for any substance.