You’re hanging out for a sandwich, but your heart sinks when you find the cheese is sporting a blue and white bloom and the bread is covered in white fluffy spots.
Can you attempt a rescue operation by cutting off the mould or should the whole lot go in the bin?
The answer to some extent depends on how you balance your approach to a potential health risk versus your desire to avoid wasting food.
If the cheese is a hard cheese, it’s probably safe just to cut the bad bit off, says Dr Ailsa Hocking, of CSIRO Agriculture and Food.
The bread though, is probably better off thrown away, she believes.
Assessing the risk
It’s not just an awful taste you’re risking if you eat mouldy food.
Actively growing mould can release toxins into food.
Since the spread of the tiny mould tips is not always visible, it might be hard to know where it (and hence the toxin) is.
So how do you decide what to do when you haven’t got a food safety expert on hand?
Two factors that should guide you are the moisture content of the food and how densely it’s structured, Dr Hocking says.
The low moisture content and dense structure of hard cheese means mould will usually survive only on the surface, rather than spreading invisibly into the cheese, Dr Hocking says.
So it should be safe to cut around the affected area and eat the rest of block. But she advises cutting with a margin of a couple of centimetres, just to be on the safe side.