Ever since food technologists developed the ‘Flavor Saver’ tomato in the US in the 1990s, the humble red fruit has found itself right in the glare of the genetically-modified spotlight. But how can you tell whether your tomato paste contains genetically modified tomatoes? Could you tell by looking at it? Not a chance, not even with a magnifying glass. But if you had a whole tomato you could take it to a lab and have them run a test called polymerase chain reaction (PCR). Genetically modified (GM) tomatoes have had genes added, sometimes from completely different species, to give them a desirable quality not normally found in tomatoes, e.g. resistance to frost. The genes are added using specific, identifiable pieces of DNA and it’s these pieces of DNA that the PCR test can pick out. The problem with tomato paste is that when the tomatoes get mushed up, the DNA structure is destroyed along with the structure of the tomato. Tomato paste can also be made from 6 or 7 varieties of tomato, so the only way to tell if your paste is completely GM-free is to go back to the source of the tomatoes and find out which types were planted in the first place. Alternatively, you could just look at the packet – UK law says that all GM foods must be clearly labelled! Go back