dvgw-technologiezentrum wasser (tzw), karlsruhe twinning project pl06/ib/en/01 taste and odor...

DVGW-Technologiezentrum Wasser (TZW), Karlsruhe

Twinning Project PL06/IB/EN/01

Taste and odor assessment in Taste and odor assessment in

the framework of water quality the framework of water quality

monitoringmonitoring

Dr. Frank Sacher




Introduction Regulation Sensory perception

Analysis of taste and odor compounds Chemical analysis of single compounds Electronic instruments Odorimetry

Procedures for determination of taste and odor German Standard DIN 38403, part B1/2 EN 1622 Taste and odor determination at TZW

Conclusions

OutlineOutline



Council Directive 98/83/EC on the quality of water Council Directive 98/83/EC on the quality of water intended for human consumptionintended for human consumption

ANNEX I, Part C: Indicator parameters (…) Odour: Acceptable to consumers and no abnormal change (…) Taste: Acceptable to consumers and no abnormal change (…)

ANNEX III: Specifications for the analysis of parameters (…) 3. Parameters for which no method of analysis is specified

Odour Taste



ANNEX 3: Indicator parameters (…) Odor: Threshold number of 2 at 12 °C and of 3 at 25 °C

Comment: Dilute stepwise with water free of smell and test for odor. Taste: Acceptable to consumers and no abnormal change (…)

ANNEX 5: Specifications for the analysis of parameters (…) 3. Parameters for which no method of analysis is specified

Odor Taste

German Drinking Water Directive (TrinkwV 2001)German Drinking Water Directive (TrinkwV 2001)



Summary: Directives on the quality of water intended Summary: Directives on the quality of water intended for human consumptionfor human consumption

For the parameters taste and odor Council Directive 98/83/EC

does not give any parametric values nor does it specify any

methods for analysis or any performance characteristics.

The German Drinking Water Directive gives a threshold value for

odor but not for taste. It does also not specify any methods for

analysis or any performance characteristics.

BUT: Taste and odor problems are among the most frequent

and the most serious complaints from consumers.



Chlorine-like

Swimming pool-like

Ozone

Mineral oil-like

Muggy

Corky

Salty

…

In most cases source of complaints is difficult to determine

Taste and odor complaints from consumersTaste and odor complaints from consumers



Algae-borne compounds (e.g. geosmine, MIB) Phenols Chlorophenols Anisoles Chloroanisoles Hydrocarbons Musk compounds (nitro musks, polycyclic musks) Sulfur-containing compounds Chlorine Chlorine dioxide Ozone …

Taste and odor compounds in waterTaste and odor compounds in water



Sensory perceptionSensory perception

Single impressions

Overall impression

haptictastyolfactoryoptical

texture

flavorlook

temperaturearoma taste



Taste assessmentTaste assessment

SweetGlucose (0.08 mol/L)

Saccharose (0.01 mol/L)

Saccharine (0.000023 mol/L)

other sugars…

SourLactic acid

(lemonades, fruits, milk products, …)

Malic acid (fruits,…)

Carbonic acid (mineral water)

Citric acid (citrus fruits, lemonades,

candies,…)

SaltyTable salt (sodium

chloride; purely salty)

Potassium chloride (salty, sour and

bitter)

Magnesium chloride (salty, bitter)

Sodium bicarbonate (sweet, bitter)

Potassium sulfate (sour, bitter)

BitterMagnesium sulfate

Calcium salts

Alkaloids

UmamiGlutamic acid and its

salts



Chemical analysis of single compounds

Electronic tongues and electronic noses

Odorimetry

Analysis of taste and odor compoundsAnalysis of taste and odor compounds



Chemical analysis of single compoundsChemical analysis of single compounds

Class of compounds Representative Analytical method

Phenols 2,4,6-Trichlorophenol SPE, derivatisation, GC/MS

Ketones 2-Hexanone LLE, GC/MS

Aldehydes trans-2-Decenal LLE, GC/MS

Synthetic musks Musk-Xylene SPE, GC/MS

Algal-borne compounds Geosmine CLSA, GC/MSPurge&trap, GC/MS

Sulfides Dimethylsulfide CLSA, GC/MSPurge&trap, GC/MS

Anisoles 2,4,6-Trichloroanisole SPE, GC/MS

Pyrazines 2-Isobutyl-3-methoxypyrazine SPE, GC/MS

Organic acids Trichloroacetic acid LLE, derivatisation, GC/MS

Benzenes 1,4-Dichlorobenzene Purge&trap, GC/MS

…



Expensive

Labor intensive

Needs experienced personal

Time intensive

Laboratory-based method

Important compound might be missed

Disadvantages of chemical analysisDisadvantages of chemical analysis



Expensive

Not very sensitive

Needs experienced personal

Time intensive

Laboratory-based method

Correlation to human sensing is still limited

Not (yet) very reliable

Disadvantages of Electronic Nose technologyDisadvantages of Electronic Nose technology



German Standard Method DIN 38403, part B1/2: Qualitative

determination of taste; qualitative and quantitative determination

of odor

German Standard Method DIN 38403, part B3 = EN 1622:

Determination of the threshold odour number (TON) and

threshold flavour number (TFN)

Laboratory methods

…

OdorimetryOdorimetry



Water sample has to be transferred into an odor-free glass bottle (in practice: an odor-free glass bottle is used for sampling)

For sample transport, glass bottle has to be filled completely and has to be sealed with a stopper made of glass or teflon

Cooling during sample transport is strongly recommended

Analysis has to be done as soon as possible after sampling

Testing can only be done if danger of poisoning (intoxication or contagion) can be excluded!!!(in practice: only drinking waters are tested for taste)

Testing for taste must always be done after testing for odor as odor perception can be interfered by taste perception

German Standard Method DIN 38403, part B1/2: German Standard Method DIN 38403, part B1/2: General recommendationsGeneral recommendations



Reporting of intensity: withoutweak/poorstrong

Reporting of character: a) general: earthymuggyrottencorky…

b) differentiated: chlorine-likefish-likemercaptane-likemineral oil-like…

Temperature of testing must always be reported!!!

German Standard Method DIN 38403, part B1/2: German Standard Method DIN 38403, part B1/2: Reporting of results for qualitative Reporting of results for qualitative odorodor testing testing



Reporting of intensity: withoutweak/poorstrong

Reporting of character: a) general: saltysourbittersweet…

b) differentiated: chlorine-likefish-likesoap-like…

German Standard Method DIN 38403, part B1/2: German Standard Method DIN 38403, part B1/2: Reporting of results for qualitative Reporting of results for qualitative tastetaste testing testing



TON = Threshold odour number

A = Volume of water sample

B = Volume of water sample for comparison (free of odor)

TFN = Threshold flavour number

A = Volume of water sample

B = Volume of water sample for comparison (free of taste)

DIN 38403, part B3 = EN 1622DIN 38403, part B3 = EN 1622Determination of TON and TFNDetermination of TON and TFN

A

BATON

A

BATFN



Results may depend on the person performing the test and on

the conditions during testing Temperature

Draft

Noise

Presence of other people

Test has to be performed under standardized conditions!!! Trained personal

Quiet and air-conditioned laboratories

Practical problems with taste and odor determinationPractical problems with taste and odor determination



Sampling is done in 500 mL glass bottles with a glass stopper

Samples are stored at 4 °C until analysis

Analysis is done within 24 h after arrival of the samples in the lab

At beginning of analysis half of the volume of the sampling bottle

is decanted (and used for the determination of other parameters)

TZW procedure for qualitative odor determination (1)TZW procedure for qualitative odor determination (1)



Glass bottles are tempered for 30 min in a water-bath at 25°C




The bottle is taken from the water-bath and vigorously shaken

The stopper is removed and the smell is immediately tested by

the test person

If an odor is detected, a second person smells as well




Principle: if in a water sample an odor has been qualitatively

determined, the sample is diluted by odor-free water until no odor

can be detected anymore

Only odor intensity is taken into account!!!

Threshold odor number: TON = Total volume after dilution/Volume

of water sample

Procedure for quantitative odor determinationProcedure for quantitative odor determination



A quantitative test is only performed if qualitative testing was positive

Different volumes (0.2 mL, 2 mL, 20 mL, 200 mL) of the water sample are diluted in odor-free 500 mL glass bottles with odor-free water (tap water from Karlsruhe) to a final volume of 200 mL

Following the procedure for qualitative odor determination all samples are tested, starting from the highest diluted sample

A odor-free water sample is tested for comparison

If even the highest diluted sample exhibits a perceptible odor, 2 mL of the diluted sample containing 2 mL of the original water are diluted with odor-free water up to 200 mL

TZW procedure for quantitative odor testing: TZW procedure for quantitative odor testing: Pre-testingPre-testing



Final testing is done with the most diluted sample that exhibited a perceptible odor during pre-testing

Different volumes of this diluted water sample are further diluted with odor-free water to a final volume of 200 mL

E.g. 13, 10, 7, 5, 4, 3 mL of the original water are further diluted to 200 mL if the sample containing 20 mL of original water did exhibit a perceptible odor during pre-testing

Based on the volume of water sample in the tested water that exhibited no perceptible odor (while the sample less diluted did), the Threshold Odor Number is calculated

TZW procedure for quantitative odor testing: TZW procedure for quantitative odor testing: Final testingFinal testing



Volume of original water sample (mL)

Threshold odor number

200 1

130 1.5

100 2

70 3

50 4

40 5

30 7

20 10

13 15

10 20

7 30

5 40

…

Volume of original water sample (mL)

Threshold odor number

…

4 50

3 70

2 100

1.3 150

1.0 200

0.7 300

0.5 400

0.4 500

0.3 700

0.2 1000

0.002 100000

Calculation of TONCalculation of TON



Only drinking waters are tested for taste (no raw waters, no waters during treatment)

Only qualitative determination of taste, no quantitative determination (TFN)

If a drinking water sample exhibits a perceptible taste, the procedure is immediately stopped and the operator of the treatment plant is contacted!!!

Practical procedure for taste testingPractical procedure for taste testing



Test solutions are used for training

Training of personal - OdorTraining of personal - Odor

Compound Concentration (µg/L)

Isoamylacetate 1

Geosmine 0.01

2,4,6-Trichloroanisole 0.005

1-Octen-3-ol 5

Eugenol 5

The test solutions are tested together with odor-free samples

The person has to identify unambiguously the test solutions

among all samples



Test solutions are used for training

Training of personal - TasteTraining of personal - Taste

Compound Concentration (µg/L) Taste

Saccharose 6 Sweet

Sodium chloride 1.3 Salty

Citric acid mono-hydrate 0.4 Sour

Coffein 0.3 Bitter

The test solutions are tested together with odor-free samples

The person has to identify unambiguously the test solutions

among all samples and has to identify the taste characteristics



Compliance with recommendations of European on national Drinking Water Directives with regard to taste and odor is essential for water suppliers to keep the trust of the consumers

Testing of taste and odor is difficult and can easily become subjective

Sensory-based methods are still “the best available technology”

More advanced technologies as gas chromatography or Electronic nose & tongue technology might be helpful but can not (yet) be used on routine bases

Standardization of the methods for taste and odor testing is essential!!!!

ConclusionsConclusions

dvgw-technologiezentrum wasser (tzw), karlsruhe twinning project pl06/ib/en/01 taste and odor...

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