The detection of preservatives in beverages by a fermentation test, with special reference to brominated compounds
article
A fermentation test has been developed for detecting preservatives, other than benzoic and sulphurous acids, in soft drinks. The substrate is brought to a pH value of 5·4 ± 0· 1 and, if necessary, is enriched with 0·25 per cent. of Difeo yeast extract. Thereupon it is inoculated with approximately 10^4 cells per ml of bakers' yeast (Saccharomyces cerevisiae) and transferred to Einhorn (Smith) fermentation tubes. The gas formed is measured after incubation for 36 and 48 hours at a temperature of 24° ± 1° C.
Brominated acetic acid derivatives can be detected when present in beverages at concentrations corresponding to bromine concentrations of 0·5 to 2 mg per kilogram. Sulphurous and benzoic acids at concentrations of 75 mg per kilogram do not interfere with the test, owing to the rather high pH value. Eosin, a food-colouring material that is used in The Netherlands, only inhibits the fermentation when at least 50 mg of bromine is present per kilogram of sample.
Essential oils, tannins or other compounds present in natural fruit juices do not interfere at the concentrations that occur in fruit drinks. Citrus terpenes, which are present in some beverages, can be inactivated by adding liver particles to the fermentation medium. Under these circumstances threshold levels of detection of the various brominated preservatives vary from 1 to 10 mg of bromine per kilogram.
Brominated acetic acid derivatives can be detected when present in beverages at concentrations corresponding to bromine concentrations of 0·5 to 2 mg per kilogram. Sulphurous and benzoic acids at concentrations of 75 mg per kilogram do not interfere with the test, owing to the rather high pH value. Eosin, a food-colouring material that is used in The Netherlands, only inhibits the fermentation when at least 50 mg of bromine is present per kilogram of sample.
Essential oils, tannins or other compounds present in natural fruit juices do not interfere at the concentrations that occur in fruit drinks. Citrus terpenes, which are present in some beverages, can be inactivated by adding liver particles to the fermentation medium. Under these circumstances threshold levels of detection of the various brominated preservatives vary from 1 to 10 mg of bromine per kilogram.
TNO Identifier
288850
Source
The analyst, 78(922), pp. 37-42.
Pages
37-42
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