Agriculture Reference
In-Depth Information
a demand to identify natural preservatives from plants, animals and microorganisms.
Numerous potential natural antimicrobials have been identifi ed and in the cases of
nisin, natamycin and lysozyme have already been approved in many countries
and, in the European Union (EU), given 'E numbers'.
In principle food legislation does not differentiate between natural and synthetic
compounds. Additives are only permitted where there is a technological need,
they represent no hazard to public health and they are not misleading to the
consumer. Nevertheless, the food industry aims to exploit natural ingredients and
additives that can protect against food spoilage and control food poisoning
microorganisms, but do not have to be labelled in Europe as an E number or have
an off-putting chemical name. An E number can refer to a natural or synthetic
additive. It is ironic that E numbers assigned to permitted additives are now
widely seen as unfavourable on an ingredient list, despite the fact that the E
number should convey the message that the additive has been thoroughly assessed
for safety and is strictly controlled on how it is used. The same cannot be said of
some natural substances that are being proposed as food preservatives.
Natural of course does not necessarily mean safe. For example snake venom,
botulinum toxin and mycotoxins can be described as natural but can hardly be
described as safe. Therefore, any new preservative derived from nature should
require a full toxicological assessment before being acceptable and receiving the
necessary legislative approval to being used. Such toxicological evaluations are
extremely expensive and would be prohibitive to most if not all additive and
ingredient suppliers. There are possible exceptions that may be exempt from such
costly toxicological assessment. These exceptions could be substances already
present or used in foods that have a long history of use and are recognised as safe
at the concentrations that would be proposed for food preservation.
An ideal food natural preservative would:
•
have a broad action antimicrobial spectrum active against Gram-negative
bacteria, Gram-positive bacteria, yeasts and moulds (the so-called 'magic
bullet');
•
be cidal in action rather than inhibitory;
•
be active at low concentration;
•
be heat stable;
•
be unaffected by either low or high pH;
•
impart no fl avour or odour property to the food;
•
possess no toxicity;
•
be easily assayable;
•
have no pharmaceutical or veterinary application;
•
not allow microorganisms to develop resistance;
•
be label friendly.
In addition, and not least, it would be cost-effective to the food producer.
It is now considered doubtful whether such a single natural preservative
possessing all these properties exists and, surely if there is, it would have been
identifi ed by now. The realisation that a single natural antimicrobial will never
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