- Food retailers will not be able to rely
on tests alone to ensure that their food contains no genetically-modified
(GM) ingredients. They will have to know exactly where the foods ingredients
- This is because in some cases there is
no certain way of telling whether processed food once included ingredients
that had been genetically-modified.
- If the raw, unprocessed crop is available,
or if the food has been only lightly processed, then it is relatively easy
to tell a GM plant or ingredient from a normal one.
- This is done with a standard DNA test
called the polymerase chain reaction (PCR) that looks for and copies specific
pieces of DNA.
- But when foodstuffs are processed the
DNA they contain becomes degraded. Also substances that interfere with
the PCR reaction can be introduced during processing and cooking.
- The Laboratory of the Government Chemist,
an independent UK body says that extracting DNA from highly processed food
in a form suitable for reliable PCR testing can be "challenging and
- Last year LGC scientists warned food
manufacturers and retailers that they would be misleading customers if
they claimed that their highly processed products were 100% free of GM
ingredients based on tests alone.
- The lack of a reliable test means that
the only foolproof way to ensure that a food is GM free is to find out
exactly what it is made from. This will require finding the source of its
basic ingredients and ensuring that they are GM free.
- If the food is made from soya or maize
imported from the United States this may be impossible as GM altered soya
and maize are mixed with unaltered crops.
- As part of the requirement that GM foods
are labelled the UK government has issued a list of suppliers of certified
GM free foodstuffs.