The importance and origins of each flavour are:
Flavour: DIACETYL Chemical name: 2,3-BUTANEDIONE
“Diacetyl, like butter, butter popcorn, or warm milk”
IMPORTANCE: Diacetyl imparts a sweet, butter-like note. Its presence can be indicative of microbiological spoilage of soft drinks by lactic acid bacteria or by alcoholic yeasts.
ORIGINS: Diacetyl (2,3-butanedione) is produced by contaminant lactic acid bacteria (Lactobacillus, Pediococcus, Leuconostoc). Some yeasts produce a precursor of this compound which can give rise to 2,3-butanedione formation during product storage.
Flavour: BUTYRIC Chemical name: BUTYRIC ACID
“Butyric, like cream liqueur, toffee or baby vomit, rancid”
IMPORTANCE: Butyric acid imparts a rancid note to soft drinks, reminiscent of baby vomit, which is especially prominent in products of low pH value. While regarded as desirable in some types of confectionery, it is generally rejected by consumers of soft drinks.
ORIGINS: Butyric acid is produced in sugar syrups by bacteria, including Bacillus spp. and Clostridium spp. It is also occasionally caused by penetration of adhesive label components into soft drinks which have been packaged in plastic bottles.
Flavour: CHLOROPHENOL Chemical name: 2,6-DICHLOROPHENOL
“Chlorophenol, like antiseptic, disinfectant or mouthwash”
IMPORTANCE: 2,6-Dichlorophenol imparts an antiseptic, medicinal note to contaminated soft drinks. The taints is regarded by consumers as unpleasant and tainted even at low levels. Chlorophenols are produced through reactions involving phenolic compounds and free chlorine.
ORIGINS: Chlorophenols can taint soft drinks and juices through ingredients, water or packaging materials. Antiseptic taints due to chlorophenols are especially associated with use of recycled wood and cardboard in packaging materials.
Flavour: DMS Chemical name: DIMETHYL SULPHIDE
“DMS, like boiled sweetcorn or tomato sauce”
IMPORTANCE: Dimethyl sulphide is associated with sulphury and ‘muddy’ odours notes. It is an indicator of contamination of the carbon dioxide supply. DMS can also be associated with contamination of the water supply with faecal bacteria.
ORIGINS: DMS is a contaminant introduced to soft drinks through use of insufficiently-purified carbon dioxide. This flavour can also arise through bacterial spoilage of ingredients and additives.
Flavour: METALLIC Chemical name: FERROUS SULPHATE
“Metallic, like ink or blood”
IMPORTANCE: Metallic flavour problems are often of external origin (taints) and occasionally formed within the product itself (off-flavour). Metallic character is primarily a mouthfeel characteristicl but sometimes product odour, colour and clarity can be affected.
ORIGINS: Metallic taints in soft drinks are derived from contamination of raw materials or process water with metal ions or from or from corrosion of process plant. Metallic odours can also be produced by lipid oxidation.
Flavour: SMOKY Chemical name: GUAIACOL
“Smoky, like smoked fish or cheese”
IMPORTANCE: Metallic flavour problems are often of external origin (taints) and occasionally formed within the product itself (off-flavour). Metallic character is primarily a mouthfeel characteristicl but sometimes product odour, colour and clarity can be affected.
ORIGINS: Metallic taints in soft drinks are derived from contamination of raw materials or process water with metal ions or from or from corrosion of process plant. Metallic odours can also be produced by lipid oxidation.
Flavour: >H2S Chemical name: HYDROGEN SULPHIDE
“H2S, like boiled eggs or rotten eggs”
IMPORTANCE: Hydrogen sulphide imparts an unpleasant sulphury note to contaminated soft drinks. H2S is easily oxidized to less odour-active species, so its presence is indicative of the failure of water treatment processes or contamination arising during production of soft drinks.
ORIGINS: H2S is a contaminant of carbonated soft drinks which can be introduced through use of insufficiently-purified carbon dioxide. It can also arise through microbiological spoilage by bacteria, and through chemical reactions involving metal surfaces in canned products.
Flavour: KEROSINE Chemical name: 1,3-PENTADIENE
“Kerosine, like petroleum or geranium”
IMPORTANCE: 1,3-Pentadiene imparts a potent ‘chemical’ taint to affected products. It is typically described as kerosene-like, with additional descriptors of plastic, paint, and geranium depending on the nature of the affected product. Styrene may also be formed together with 2,3-pentadiene by some organisms. during spoilage of soft drinks and fruit juices, or the ingredients from which they are made, by moulds.
ORIGINS: 1,3-Pentadiene is produced by contaminant microorganisms. Moulds such as Penicillium and Trichoderma, and yeasts such as Zygosaccharmoyces and Debaromyces convert odourless sorbic acid used as a preservatives in some soft drinks and fruit juices into the highly odour active molecule 1,3-pentadiene.
Flavour: PLASTICS Chemical name: STYRENE
“Plastics, like polystyrene or model aeroplane glue”
IMPORTANCE: Styrene is often described by consumers as ‘chemical’, ‘plasticy’ (like polystyrene) or ‘contaminated’. When formed by yeasts or moulds, additional compounds such as 4-vinyl guaiacol and 1,3-pentadiene may be present which can modify the flavour making the drink more ‘medicinal’, ‘smoky’ in the case of guaiaco, or like kerosine in the case of pentadiene.
ORIGINS: Styrene can contaminate plastic bottles and, in turn, impart a taint to the soft drinks or juices packaged into these bottles. It can also arise from the action of contaminant yeasts and moulds. Use of defective carbon dioxide is occasionally to blame for styrene contamination incidents.
Flavour: MUSTY-TCA Chemical name: 2,4,6-TRICHLOROANISOLE
“Musty-TCA, like corked wine or a damp cellar”
IMPORTANCE: 2,4,6-Tribromoanisole imparts an unpleasant musty odour which is reminiscent of damp cellars or corked wine. This is one of the few flavours that can taint soft drinks through airborne contamination, even after the product has been packaged.
ORIGINS: 2,4,6-Tribromoanisole contaminates soft drinks through ingredients, water, air or packaging materials. Taints from such haloanisoles are associated with use of recycled materials such as wood and cardboard. 2,4,6-Tribromoanisole is derived from methylation of bromophenols by moulds.
