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The Taste of Chlorine in Water - Major Findings Clearing the Way for New Outlooks

http://www.bulletins-electroniques.com/actualites/63933.htm

As part of the Eau du robinet agréable à boire (tasty tap water), a VITAGORA accredited project also called SENS'EAU (startup in 2006), two CIFRE theses funded by the Lyonnaise des Eaux Group and supervised by the Centre des Sciences du Goût et de l'Alimentation (CSGA, Center for the Science of Taste and Food) were scheduled. One addressed consumers' perception of the taste of chlorine, a very important topic as the flavor of the chemical is the target of recurrent criticisms of tap water. The thesis on the subject, which Sabine Puget has just defended in Dijon, focused on highlighting the potential means of neutralizing the flavor in water. The important research findings have cleared the way for new exploratory paths and should lead to optimized production standards.

Water suppliers use chlorine to ensure the bacteriological quality of the product, from the treatment plant to consumers' tap. However, as everybody knows firsthand, sometimes the taste of chlorine bothers the consumers of water containing the chemical element. Notably, more than half the French perceive the chlorine in water when it has been added in concentrations compliant with the mandatory regulations for drinking water producers. The consumers clearly refer to the 'taste' of chlorine and not to its 'smell'. "When I began my thesis, the mechanisms involved in the perception of the flavor, which corresponds to all the olfactive, taste and trigeminal (retro-nasal) senses, were very little known. So, my work involved consisted in shedding light on nature of the mechanisms," Sabine Puget explained.

Major Findings

The issue has always fascinated the young Ph.D.; she attended an undergraduate course in sensory assessment at Tours University before joining the Laboratory of Sensory Neurobiology near Paris for her advanced masters on odors. After a short time at Peugeot Citroen where she worked on the methodology of sensory evaluation tailored to the touch of textiles in the automotive industry, she arrived at the Dijon CSGA where she immediately began research that highlighted that chlorine is not a taste but a smell, "high concentrations of the smell, i.e., from 4 mg/l, activate the trigeminal system." Sabine Puget later worked on comparing the perception of chlorine in two water consumer groups, one that drank tap water, the other bottled water. "We observed that drinking tap water does not seemed connected to a sensitivity to chlorine, but rather to consumers' representation of tap water," she explained.

Sabine Puget began to explore the role of the water matrix in the perception of the chlorine flavor. To do so, she used both experimental model waters with particular compositions and bottled water, both with the same proportion of chlorine. "We showed that the molarity and composition variations in the cations of the water modulate its taste. We also highlighted a modulation of chlorine intensity according the mineral matrix of the water," she said. Her research showed that consumers perceived the water with weaker overall minerality and with substantial amounts of sodium as having more taste, but also as being more chlorinated. "This is extremely valuable information for water producers," she exclaimed. Actually, the chlorine flavor stands to increase according to initial water minerality. So, producers have to find the right balance to satisfy consumers.

A Thesis Paving the Way for New Exploratory Paths

"Aside from the thesis, the challenge is to try and neutralize the chlorine taste in tap water by using sensory neutralizers," pointed out Sabine Puget. So, she has begun to explore the perceptive interactions between an allegedly neutralizing aroma added to drinking water and the chlorine flavor. "Findings have shown that adding an aroma at the peri-liminal level increases the perception of the chlorine flavor and lowers consumer acceptability," she underscored. On the other hand, some aromas at higher concentration levels, such as cinnamon, seem able to lower the perception of chlorine. "The problem is that these conditions are incompatible with the constraints for supply water," she hastened to add.

The thesis that Sabine Puget has just defended has provided several important answers, especially for water producers, but she has also paved the way for new paths to explore. For instance, it seems that saliva pH plays a part in the perception of chlorine, a hypothesis that still has to be confirmed. Sabine Puget is now tackling other fields but still in within the scope of sensoriality, with a focus on odors and taste. She has just joined the research center of a major cigarette maker. "Odor is the common thread running through my incipient career as researcher," she said with a smile. As cigarettes are a blend of complex odors, she must be satisfied.

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Sabine Puget - email: sabinepuget@yahoo.fr

Code brève
ADIT : 63933

ADIT - Jean-François Desessard - email: jfd@adit.fr

eTech France numéro 243 (5/07/2010) - ADIT / ADIT - http://www.bulletins-electroniques.com/actualites/63933.htm