ESR food forensic scientists say they have several ways of working out whether an object found in food has been put there maliciously or accidentally.
Several cases to hit the headlines recently have involved fresh produce containing foreign objects such as needles.
It’s a scenario that ESR has encountered from time to time.
ESR food forensic scientist Darren Saunders says one of the first things to establish in such cases is whether there are fingerprints or DNA on the container.
“Then there is the identification of the foreign objects themselves – if you have a thumb tack, needle or a pin you look at simple measurements, like dimensions, then compare it to what’s commercially available, analyse its composition – what sort of metal is it – where are these available and so forth,” Mr Saunders says.
Foreign objects in food are one of the big concerns ESR gets from manufacturers and suppliers, who want to know where the responsibility lies.
“They will want to know if it is a malicious case of someone inserting, for instance, something sharp and horrible into their bread. They’ll want to know whether it was baked in.
“We had a series of cases with needles found in baked bread and you could tell from the bag by the tiny holes in it that something had been inserted and which direction it came from – that is from the outside.”
Mr Saunders says another complaint ESR frequently gets relates to suspect rodent droppings, which – on the face of it – can be hard to tell from bits of burnt grease or other food ingredients.
“But under the microscope, you’ll find faecal material which contains the rodent’s hair,” he says.
“That’s because they’re always grooming and consuming their own hair, and hair can often be identified down to a species level. Mice hairs for instance are very characteristic.”
One complaint involving hair came from a milk company, which was continually finding ginger hairs in its on-line filter.
“We identified it as coming from a cat, so you get this image of the cat waiting until night time and jumping into the vat. Literally, the cat that got the cream!”
You can listen to Darren Saunders explain his work here.