By Anna Chisholm for the ABC
Experts say while mould can be cut away from some foods, it's often better to discard food that has visible mould. Photo: Tim Hester
Have you ever been tempted to cut off a mouldy corner of cheese?
You might be throwing together a last-minute meal and trying to avoid a trip to the shops.
Or maybe one of your parents would insist it was "still good". But is it?
Here's what experts had to say about whether food that has gone a little mouldy is ever really "still good".
Can you cut around mould?
It depends.
Food safety scientist at the CSIRO Rozita Vaskoska says, "you can only cut the mould off if the food is really hard."
Vaskoska uses the example of a hard cheese, and says some hard fruit and veg might also fit into this category.
Whenever the food is soft or semi soft, it's not recommended to cut out the mould because … the toxins that mould produce might penetrate the depth of the food."
Vaskoska says its best to throw things like sauces, pastes, and bread away.
Tom Ross, a specialist in food microbiology at the University of Tasmania, says some foods are intentionally mouldy.
"We deliberately put blue moulds into cheese, and we love it because it tastes better."
It's things like tomato paste that Ross commonly finds mouldy in his fridge. "That goes for me," he says.
"For firmer foods … it's okay to cut mould away to a depth of at least 1 - 1.5cm."
"The best strategy is to err on the side of caution," he says, because "of the ubiquity of spores, the potential severity of exposure to the toxins, and because we don't know which ones are growing on our foods."
Ross also warns that "mouldy food often doesn't taste that good."
Photo: Unsplash
Why does food go mouldy?
Ross says moulds are fungi.
"They can exist as single celled microorganisms, which you'll never see but … when they grow collectively they form something that's visible.
"As they grow, what they're doing is trying to find new sources of nutrients, and that's why they spread."
Vaskoska says mould growth is influenced by a number of factors.
"The more moist the food, the more likely mould will grow," she says.
"The second factor is temperature, so the higher the temperature … that will increase the likelihood of growth of moulds."
"The last one is the acidity," Vaskoska says. Some foods are too acidic or too alkaline to be easily susceptible to mould growth.
Stephanie Partridge, an accredited dietician, and senior research fellow at the University of Sydney says, "fruit or veg that has a high-water content is likely to be more susceptible to mould."
She says you can look up lots of tips and tricks for storing fruit and veg online.
Is eating mould bad for you?
Vaskoska says mould itself "is not necessarily dangerous", but some moulds can produce toxic compounds called mycotoxins.
"Regular consumption of small amounts of mycotoxins can have some more severe effects, such as carcinogen."
When ingesting mould, there's also a risk that it can make you sick.
Ross says the "long-term risk to personal health from mouldy food in our kitchens and fridges" is "very low, unless a person is always cutting mould off or away all the time, and eating the remainder".
"The risk would be higher from 'wet' food or bread because even though you can remove the visible mould, the toxins produced can have spread through the moisture to other places in the food where you cannot see them."
Ross says, "if you can afford to throw it out, throw it out."
Partridge says, "it's probably not worth the risk of trying to salvage [food that's a bit mouldy].
"Particularly for people who are pregnant, immunocompromised, elderly, have other health complications, it's generally not a good idea," she says.
- ABC