Why does tap water have a taste or smell ? Odorless or tasteless water does not exist, neither does chemically pure water in its natural state. Water can be tasted like wine, its taste and smell can be enjoyed, sought out and compared as is illustrated by the recent opening of water bars.
Scientific chronicle : the taste and smell of water
Yet, saying that tap water has a taste or smell would imply that it has a bad taste or a bad smell, which would lead to reluctance to drink it and fear for one's health.
- Download the magazine of the scientific chronicles "The taste and smell of water" (pdf - 604 ko)
However subjective these sensory perceptions may be, the dissatisfaction which they cause is nonetheless real.
According to a recent parliamentary report in 2002, 40% of the French population found that water had an unpleasant taste.
What makes water taste unpleasant? For over 5 years, researchers at Veolia have been working towards finding an explanation. They have been breaking down, identifying, characterizing and finding the sources of compounds contained in water in order to neutralize them and give water a pleasant
Video
David Benanou (Head of the Chemical Expertise Team of Veolia Eau's Water Research Center) answers Gwenaelle Bru's questions (Veolia Industrial Markets Division) about the taste and smell of water.
Location: Water Research Center, Maisons- Laffitte (France)
Click on the screen to launch the video.
Extracts from the magazine "The taste and smell of water"
Taste and smell hand in hand
Taste and smell are so connected that the term flavour refers to the taste and smell sensations experienced when tasting.
The four fundamental tastes- sweet, salty, sour and bitter- are recognized by taste buds, while others such as chlorine, earthy, muddy and moldy tastes are more perceived by thenose, notably because of the communication between the back of the mouth and the nasal cavity.
Some smells enter directly through the nose and are perceived when we breathe. Others, i.e. aromas, reach the nose through the back of the mouth, when we eat or drink (retronasal olfaction).
80% of taste is perceived retronasally, 10% nasally and another 10% by taste buds. This goes to show howimportant the sense of smell is in tasting. Savouring water can be a true nasal experience!
Twister™, the odor stealer
Invented in 1999 by the Belgian chemist, Pat Sandra to concentrate volatile compounds in a liquid solution in order to identify them, Twister™ is a small magnetic bar, 1 to 2 cm long and 1 mm in diameter, inserted inside a thin layer of glass covered in silicone. The magnet makes the device spin when it is plunged in the liquid - hence the name Twister - in order to speed up the transfer of compounds.
The silicone then stores them. Veolia came up with the idea of using this piece of equipment as an odor trap, indeed as a hook, fixing device and detector in one. By simply plunging it for 2 hours in a watersample, it picks up on and takes a print of the smells; after steeping it in a 250° environment, it will release them. This user-friendly device (it can even be used by the general public) has the main advantage of being able to store volatile compounds as opposed to transferring, which encourages loss. In order to "steal a picture" of particularly fleeting odors, it can even be used a few days running as a "camera", preserving the memory of water's journey in the networks.
Also in this magazine of the scientific chronicles
« In the absence of adequate tools, studies on the organoleptic characteristics of water have recently started. »
Interview of David Benanou, Head of the Chemical Expertise Team of Veolia Eau's Water Research Center.
What are the complaints about?
The main complaints that Veolia's research must resolve, relate to chlorine and moldy tastes.
Unknown odorous moleculs identified in Sweden.
Water has smelled moldy in Nortalje for the past ten years. After
managing the drinking water plant in this town of approximately
35,000 inhabitants since 2003, Veolia has now found the solution to
this problem and has started altering processes accordingly.
It all starts with tasting.
Tasting is the very foundation of research on the taste of water. Pinpointing a smell or a taste and defining it with words helps to steer analytical studies in the right direction.
"Perceptions in water taste vary from one country to another and depend in part on consumption habits."
3 questions to Geneviève Leboucher, Head of Veolia Eau's Marketing Division
Seizing the elusive
By studying the smell and taste of water, researchers have tackled the complex world of subtlety and volatility. in order to find the cause of bad taste, they have to use their intuition and turn to extremely sensitive and sophisticated investigative and analytical technologies: with a dilution rate in picograms (10-12 g/L).
Rennes continues to recapture the taste of water.
According to a CECOP 2005 survey, 58% of Rennes' inhabitants are satisfied with the taste of tap water compared to 38 % in 2003. Out of the third of the population declaring themselves regular drinkers of tap water, 84% of them are satisfied with it. When water was no longer attractive because of its chlorine taste, jugs of water started to reappear on restaurant tables and in school canteens. A look into Veolia Eau's project to recapture the taste of water in Brittany's capital city over the past 4 years.