A preservative is a substance that enables products such as soft
drinks to have a longer shelf life by inhibiting or arresting the
growth of micro-organisms such as yeasts, moulds and bacteria.
Not all soft drinks contain preservatives. The need for a
preservative is dependent upon the type of product and the
processing used. For example, fruit juices are aseptically filled
so that they contain no potential spoilage organisms. Bottled
waters are hygienically filled and do not contain enough nutrients
to support the growth of organisms. In both cases, preservatives
are not needed and may not be used.
The presence of carbon dioxide in a soft drink prevents mould
growth, and high levels of acidity and carbonation also help to
inhibit the growth of yeasts and lactic acid bacteria. Soft drinks
formulated in this manner do not require additional preservative
provided reasonable hygiene standards are maintained.
The presence of fruit or fruit juice in a product provides
additional nutrients which may enable organisms to grow despite the
high levels of acidity and/or carbonation. Therefore the soft
drinks most likely to ferment are mildly acid types with low
carbonation and containing fruit juice. In these cases a
preservative must be added to prevent microbiological spoilage.
There are only four preservatives currently used by the soft
The levels of preservatives permitted by the EU Directive are
based upon technological necessity, and therefore are dependent
upon the type of product. Bacteria and yeasts differ in their
susceptibility to different preservatives, so a mixed preservative
system is generally used to provide maximum protection against a
range of organisms.