benzaldehyde
“Almond , like bitter almonds or marzipan”
benzaldehyde
1.5 mg per capsule
Technical specification
Assessment
The best way to assess almond flavour in water is to cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
1.5 mg per capsule Threshold
The flavour threshold of benzaldehyde in water is 500 µg / l. Origins
Benzaldehyde is derived from the breakdown of organic material and through the action of microorganisms, including Actinobacteria, Pseudomonads and algae. Importance
Benzaldehyde imparts a pleasant, but nevertheless atypical, sweet odour to water, reminiscent of almonds or marzipan. CAS registry number
The CAS registry number for benzaldehyde is 100-52-7. Other names
benzene carbaldehyde
benzene carbonal
benzene carboxaldehyde
benzene methylal
benzoic aldehyde
benzoyl hydride
bitter almond oil
phenyl methanal
Remarks
In plant material, benzaldehyde is derived from enzymic breakdown of amygdalin. Threshold distribution
Capsules per pot
10
2-bromophenol
“Bromophenol , inky, like a museum or old TV set”
2-bromophenol
2.0 µg per capsule
Technical specification
Assessment
The best way to detect bromophenol taints in water is, without covering the glass,to swirl the sample to release the aroma before taking a single short sniff. Repeat as necessary. Amount of flavour per capsule
2.0 µg per capsule Threshold
The flavour threshold of 2-bromophenol in water is 50 ng / l. Origins
Bromophenols are produced through reaction of phenolic compounds (for example from waters associated with peaty soils) and free bromine. They can also arise due to trace contamination of water with wood preservatives and fire retardants. Importance
2-Bromophenol Imparts an unpleasant ‘tainted’ note to water. It is often described by consumers as ‘chemical’ or ‘contaminated’, even when present at low levels. CAS registry number
THe CAS registry number of 2-bromophenol is 95-56-7. Other names
bromophenol
o-bromophenol
ortho-bromophenol
Remarks
Water pH is important in determining the rate of formation of bromophenols. They can occasionally be produced by bacteria in combination with compounds such as guaiacol. Threshold distribution
Capsules per pot
10
β-cyclocitral
“Tobacco-like , like grass, hay or dry wood”
β-cyclocitral
440 µg per capsule
Technical specification
Assessment
Cyclocitral can be best detected in water in the following way. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
440 µg per capsule Threshold
The flavour threshold of beta-cyclocitral in water is 150 ng / l. Origins
Beta-Cyclocitral is formed by Cyanobacteria in reservoirs or water distribution systems. It is produced by both actively-growing organisms and through cell lysis or decomposition. Importance
Cyclocitral imparts an aromatic odour to water, reminiscent of hay and dry wood at low concentrations, which becomes more tobacco-like and fruity at higher concentrations. CAS registry number
The CAS registry number of beta-cyclocitral is 432-25-7. Other names
beta-cyclocitral
2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde
2,6,6-trimethyl cyclohexene-1-carbaldehyde
2,6,6-trimethyl-1(2)-cyclohexen-1-carboxaldehyde
2,6,6-trimethylcyclohexene-1-carbaldehyde
Remarks
Beta-Cyclocitral is associated with cases of algal bloom in lakes and reservoirs. It may be found in tainted water, together with other carotenoid breakdown products such as beta-ionone. Threshold distribution
Capsules per pot
10
dimethyl sulphide
“DMS , like sweetcorn or tomato sauce”
dimethyl sulphide
60 µg per capsule
Technical specification
Assessment
The best way to assess DMS flavour in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
60 µg per capsule Threshold
The flavour threshold of dimethyl sulphide in water is 20 µg / l. Origins
DMS is formed by bacteria growing in water. It can also arise from decomposition of algae in surface waters following an episode of algal bloom. Importance
Dimethyl sulphide is associated with sulphury and ‘muddy’ odours notes. The presence of DMS can also be indicative of contamination of the water supply chain with faecal bacteria. CAS registry number
The CAS registry number of dimethyl sulphide is 75-18-3. Other names
DMS
dimethyl monosulfide
methylsulfanylmethane
methyl monosulfide
methane thiomethane
methyl sulfide
methyl thioether
methylsulfanylmethane
2-thiapropane
thiobis(methane)
thiobismethane
Remarks
Indole and skatole may often be found in water in which the DMS has been produced by bacteria. 2-Pentanone may be present in water in which the DMS has been formed by algae. Threshold distribution
Capsules per pot
10
dimethyl trisulphide
“Onion , like stagnant water or decaying vegetation”
dimethyl trisulphide
330 ng per capsule
Technical specification
Assessment
The best way to assess onion flavour in water is as follows. Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
330 ng per capsule Threshold
The flavour threshold of dimethyl trisulphide in water is 110 ng / l. Origins
Dimethyl trisulphide is formed through decay of grass and vegetation in reservoirs and lakes and by bacterial action. It can also arise from decomposition of algae following an episode of algal bloom. Importance
Imparts an unpleasant ‘swampy’ odour to water. The intensity of the odour can be increased by the presence of other sulphur compounds. CAS registry number
The CAS registry number for dimethyl trisulphide is 3658-80-8. Other names
DMTS
1,3-dimethyl trisulfane
methyl trisulfide
methyl trithiomethane
methylsulfanyldisulfanylmethane
methyltrithiomethane
2,3,4-trithiapentane
methylsulfanyldisulfanylmethane
Remarks
Dimethyl trisulphide is often found in water in association with other sulphur compounds such as H2 S and methanethiol. Threshold distribution
Capsules per pot
10
cis -3-hexenol“Freshly cut grass , like hedge cuttings”
cis -3-hexenol
cis -3-hexenol2.9 mg per capsule
Technical specification
Assessment
Grassy taints in water in water can be detected in the following way. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
2.9 mg per capsule Threshold
The flavour threshold of cis-3-hexenol in water is 950 µg / l. Origins
3-Hexenol is derived from leaching of chemicals from grass and vegetation, and from growth of algae. The compound is produced in plants through the action of the enzyme lipoxygenase. Importance
cis-3-Hexenol imparts a pleasant, but nevertheless atypical, grassy note to water. The compound often occurs in association with cis-3-hexenyl acetate. CAS registry number
The CAS registry number of cis-3-hexenol is 928-96-1. Other names
(Z)-hex-3-en-1-ol
cis-hex-3-en-1-ol
(Z)-3-hexen-1-ol
beta,gamma-hexen-1-ol
cis-3-hexen-1-ol
(Z)-3-hexenol
cis-3-hexenol
beta-gamma-hexenol
leaf alcohol
Remarks
cis-3-Hexenol is unstable at high pH values and does not survive well in alkaline waters. Threshold distribution
Capsules per pot
10
hydrogen sulphide
“H2 S , like boiled or rotten eggs”
hydrogen sulphide
18 µg per capsule
Technical specification
Assessment
The best way to detect hydrogen sulphide in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
18 µg per capsule Threshold
The flavour threshold of hydrogen sulphide in water is 4 µg / l. Origins
H2 S is formed by anaerobic sulphate-reducing bacteria from sulphate, by Clostridium or Bacillus from sulphite or proteins, or by electrochemical action through corrosion of pipes in systems with very low flow rates. Importance
H2 S imparts an unpleasant sulphury note to water. H2 S is easily oxidized to less odour-active species, so its presence is indicative of the failure of water treatment processes or post-treatment contamination. CAS registry number
The CAS registry number of H2 S is 7783-06-4. Other names
H2 S
hydrogen sulfide
dihydrogen monosulfide
dihydrogen monosulphide
hydrogen sulfuric acid
hydrogen sulphuric acid
sulfur hydride
Remarks
H2 S is often found in association with other sulphur compounds such as methanethiol and dimethyl trisulphide. Be careful not to overexpose yourself to samples with H2 S. The more you look for it the less likely you are to find it. Threshold distribution
Capsules per pot
10
indole
“Indole , like pigs on a farm”
Technical specification
Assessment
The best way to for tasters to detect indole in water is as follows. Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
60 µg per capsule Threshold
The flavour threshold of indole in water is 20 µg / l. Origins
Indole is formed by bacteria growing in water, or contributed, pre-formed, by ground water pollution. Importance
In addition to contributing an unpleasant farmyard note, the presence of indole can also indicate contamination of the water supply chain with faecal bacteria. CAS registry number
The CAS registry number for indole is 120-72-9. Other names
2,3-benzopyrrole
ketole
1-benzazole
Remarks
DMS and skatole may often be found in water which contains indole. Big differences in perception of individual tasters result in about half regarding this flavour as a serious fault and half being oblivious to it. Threshold distribution
Capsules per pot
10
β-ionone
“Violets , like Turkish delight”
β-ionone
40 µg per capsule
Technical specification
Assessment
The best way to detect taints caused by beta-ionone in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
40 µg per capsule Threshold
The flavour threshold of beta-ionone in water is 13 µg / l. Origins
Beta-ionone is formed by algae or Cyanobacteria growing in water and through the biochemical decay of grass and vegetable matter in lakes and reservoirs. Importance
Beta-ionone imparts a pleasant, but nevertheless atypical, sweet aromatic odour to water, reminiscent of violets. It is derived from the breakdown of plant-derived carotenoids. CAS registry number
The CAS registry number of beta-ionone is 14901-07-6. Other names
ionone
beta-cyclocitrylidene acetone
beta-irisone
4-(2,6,6-trimethyl cyclohex-1-ene-1-yl) but-3-ene-2-one
4,2,6,6-trimethyl-1-cyclohexen-1-yl-3-buten-2-one
4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one
4-(2,6,6-trimethyl-1-cyclohexenyl)-3-buten-2-one
(E)-4-(2,6,6-trimethyl-1-cyclohexenyl)but-3-en-2-one
Remarks
Taints due to beta-ionone in water are associated with cases of algal bloom in lakes and reservoirs. This compound may occur together with other carotenoid breakdown products such as Β--cyclocitral Threshold distribution
Capsules per pot
10
methanethiol
“Mercaptan , like drains or rotting garbage”
methanethiol
1.0 µg per capsule
Technical specification
Assessment
The best way to assess mercaptan flavours in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
1.0 µg per capsule Threshold
The flavour threshold of methanethiol in water is 330 ng / l. Origins
Methanethiol is formed in water by anaerobic sulphate-reducing bacteria and Cyanobacteria or by decay of grass or algae in lakes or reservoirs. It can also arise from decomposition of algae following an episode of algal bloom. Importance
Methanethiol imparts an unpleasant sulphury note to water. It is easily oxidized to less odour-active species, so its presence is indicative of the failure of water treatment processes or post-treatment contamination. CAS registry number
The CAS registry number of methanethiol is 74-93-1. Other names
methyl mercaptan
mercaptomethane
methane thiol
methyl sulfhydrate
thiomethanol
thiomethyl alcohol
Remarks
Methanethiol is often found in association with other sulphur compounds such as H2 S and dimethyl trisulphide. Be careful not to overexpose yourself to samples with methanethiol. The more you look for it the less likely you are to find it. Threshold distribution
Capsules per pot
10
skatole
“Skatole , like animal faeces”
skatole
2.0 µg per capsule
Technical specification
Assessment
The best way to detect faecal odour in water is as follows. Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Amount of flavour per capsule
2.0 µg per capsule Threshold
The flavour threshold of skatole in water is 700 ng / l. Origins
Skatole is formed by bacteria growing in water, or contributed, pre-formed, by ground water pollution. It is produced by bacteria from tryptophan. Importance
In addition to contributing an unpleasant, somewhat nauseating, faecal note to water, the presence of skatole can also indicate contamination of the water supply chain with faecal bacteria. CAS registry number
The CAS registry number for skatole is 83-34-1. Other names
beta-methyl indole
β-methylindole
scatole
skatol
3-methylindole
3-MI
3-methyl-1H-indole
3-methyl-4,5-benzopyrrole
Remarks
Indole and DMS may often be found in water which contains skatole. Threshold distribution
Capsules per pot
10
2,4,6-trichloroanisole
“Musty , like corked wine or a damp cellar”
2,4,6-trichloroanisole
73 ng per capsule
Technical specification
Assessment
The best way to detect 2,4,6-trichloroanisole in water is as follows. Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
73 ng per capsule Threshold
The flavour threshold of 2,4,6-trichloroanisole in water is <10 - 30 ng / l. Origins
2,4,6-Trichloroanisole is derived from methylation of chlorophenols by moulds or Actinobacteria, primarily in water distribution systems. Importance
2,4,6-tTichloroanisole Imparts an unpleasant musty odour to water which is reminiscent of damp cellars or corked wine. CAS registry number
The CAS registry number of 2,4,6-trichloroanisole is 87-40-1. Other names
methyl 2,4,6-trichlorophenyl ether
1,3,5-trichloro-2-methoxybenzene
TCA
Remarks
2,4,6-Trichloroanisole is one of several chloroanisoles that can taint water. The flavour produced by this compound is typical. This compound can be detected, but not recognized at concentrations well below the recognition flavour threshold. Threshold distribution
Capsules per pot
10
