21 October 2014 Last updated at 23:07 GMT
British families throw away about seven million tonnes of food and drink every
year, enough to fill Wembley stadium to the brim. Most of it is beyond its
sell-by date, but how much could be safely eaten, asks Michael Mosley.
I've agreed to feast on a range of foods that have gone beyond their prime,
guided by mould expert, Dr Patrick Hickey.
I realise it is going to be an unusual lunch when Hickey passes me a disposable
contamination suit to wear. Before tucking in he also warns me that we will not
be eating any foods that have passed their "use by" date. To do so would risk
serious food poisoning.
With "best before" or "sell by" things are more flexible.
Our first course was some ageing cheddar. As he cuts away the mouldy part
(being careful that the knife doesn't get contaminated by mould) he assures me
the rest is safe to eat. Cheddar and parmesan are dry cheeses and because mould
needs moisture to thrive, it doesn't normally penetrate far below the surface.
Some cheeses, of course, are deliberately infected with fungi. Penicillium
roqueforti gives blue cheeses such as stilton and roquefort their flavour.
With most soft cheeses, however, unless the fungus has been deliberately
introduced, the presence of mould suggests infection not just by unwelcome
fungi but also harmful bacteria, such as listeria or salmonella. If that
happens, throw it away.
Next, he pulls out some bread covered in small bits of white-and-blue mould. He
assures me that it will be fine, toasted, once the mouldy crusts have been cut
off. "The moulds don't go deep," he says. "The time you really need to be
worried about bread is when it has black bits on it." I decide to pass.
Then he digs out some long-forgotten vegetables from the back of a fridge. The
courgettes and carrots are covered in a horrible slime, which Hickey tells me
is caused by bacterial colonies growing on the surface. Could I boil these up
for soup?
"If you did," he says, "you'd probably develop terrible stomach ache in a
couple of hours, followed by stomach cramps and diarrhoea"
So best thrown out.