Preservative analysis using ion chromatography

Preservatives such as sodium benzoate or potassium sorbate enable soft drinks to have a longer shelf-life by inhibiting or arresting the growth of micro-organisms.

And now ion chromatography can provide a cost effective yet precise technique for the analysis of these preservatives, claims equipment supplier Metrohm.

The presence of carbon dioxide in soft drinks prevents mould growth and the high levels of acidity and carbonation help to inhibit the growth of yeasts and lactic acid bacteria. Conversely those beverages that contain fruit or fruit juices provide additional nutrients that may enable organisms to grow despite the levels of acidity and carbonation.

The soft drink products most likely to ferment are mildly acidic types with low carbonation containing fruit juice and in these instances a preservative is added to prevent micro-biological spoilage.

Sodium benzoate is effective against yeasts and moulds but can prove difficult to dissolve and can also impart a slight flavour at high levels.

Potassium sorbate, meanwhile, is more effective at lower acidities but is much more expensive and less effective against certain strains of bacteria. In cold conditions its solubility is reduced and it can suppress the flavour of the drink.