Field guide · food safety
Sometimes you can cut mould off. It depends entirely on the food.
The extension-service rule of thumb: which foods a generous trim can save, which go in the bin whole, and why texture is the deciding factor.
Read with sources
The short answer: the UK's Food Standards Agency advises not eating food that is obviously rotten or mouldy at all — an instruction it stresses for children, people who are pregnant, people over 65 and anyone with a weakened immune system — because removing the mould and the food around it is no guarantee the unseen toxins are gone. Source: FSA home food fact checker (opens in a new tab). US food-safety guidance is more permissive on hard, dense foods — hard cheese, dry-cured salami, firm vegetables — where trimming at least an inch around and below the spot can be enough, because mould's threads struggle to travel inside dense food. On anything soft, moist or porous — bread, soft cheese, yogurt, jams, cooked leftovers — invisible threads and any toxins can run right through it, so the whole thing goes either way. When in doubt, throw it out. Source: Ohio State University Extension (opens in a new tab).
Why the answer depends on the food's texture
The fuzz you see is only part of the mould. A mould filament — called a hypha — forms thread-like growth that can penetrate below the surface, and mouldy food may also have invisible bacteria growing alongside it. Some moulds can produce mycotoxins, which are often heat-stable, so cooking does not reliably remove them. Source: OSU Extension, mould on food (opens in a new tab).
Texture is the deciding variable because it decides how far the invisible part travels. In hard, dense food the surface limits how far hyphae and any toxins diffuse; in soft or moist food there is no such limit, and contamination can run through food that still looks clean. That is why the same green spot means "trim generously" on a cheddar and "bin it" on a soft cheese. Source: OSU Extension, mould on food (opens in a new tab).
Foods where cutting works
The trim-and-keep list is short and firm-textured: hard cheeses like cheddar, hard meats like dry-cured salami, and firm vegetables like cabbage, carrots and peppers. On those, the extension guidance is to remove the moulded portion and use the rest. Source: OSU Extension, mould on food (opens in a new tab).
The trim has rules of its own. Cut at least an inch outside and below the visible growth — the hyphae you cannot see extend past the fuzz you can. Keep the knife out of the mould itself so it does not carry contamination into the clean part, and re-cover the food in fresh wrap afterwards. The generous margin is the point; shaving the visible spot off leaves the threads behind. Source: OSU Extension, mould on food (opens in a new tab).
Foods where it doesn't
The discard list is longer and softer: soft cheeses, yoghurt and other dairy; bread and baked goods; jams and jellies; soft fruit and vegetables; nuts and peanut butter; sliced or cooked meats; cooked leftovers and casseroles. For those, the guidance the extension relays is to discard the food — the mould's threads and any mycotoxins can already be throughout. Source: OSU Extension, mould on food (opens in a new tab).
Two discards carry extra weight. Mouldy beverages — opened juice left too long, forgotten coffee — are thrown out because any mycotoxin diffuses through the liquid, so removing the surface mould removes nothing. And mould on home-canned food is a different emergency: it can signal a seal or processing failure that lets far more dangerous bacteria in, so it is discarded outright. Source: OSU Extension, mould on food (opens in a new tab).
One edge case is worth knowing in the other direction: mould or kahm yeast on a vegetable fermentation like sauerkraut can be skimmed off if caught quickly — a narrow exception for a salted, brined environment, not a general licence. Source: OSU Extension, mould on food (opens in a new tab).
Mould that's supposed to be there
Some foods are made by mould. Blue-veined cheeses and mould-ripened rinds like brie's are fermented with moulds chosen for the job — part of how the product becomes itself — so the mould on a deliberately mould-ripened cheese is a feature, not spoilage. Source: OSU Extension, mould on food (opens in a new tab).
The distinction that matters is which mould. Spoilage mould growing on a soft cheese that is not part of its manufacturing — the example the extension gives is blue mould on feta — means discard, even though mould on a blue cheese is fine. And when surface mould appears on a hard blue like stilton, US guidance treats it like other hard cheese: trim at least an inch around and below it. Source: OSU Extension, mould on food (opens in a new tab).
Don't sniff it — what to do instead
The instinct to smell-test a mouldy item is the one to resist: mould can cause allergic reactions and respiratory problems, and a close sniff is exactly how spores get inhaled. Look, don't smell. If the food is covered in mould, the US guidance is to wrap it or bag it and put it in a covered bin children and animals cannot reach. Source: OSU Extension, mould on food (opens in a new tab).
Then clean where it sat. Mould spores spread, so the shelf or drawer the food touched wants a wipe, and neighbouring food wants a check — mould spreads quickly in fruits and vegetables stored together. The container can be washed with warm soapy water and reused. Source: OSU Extension, mould on food (opens in a new tab).
Prevention: buy less, store better
The cheapest mould strategy is not needing one: buy smaller amounts, keep the fridge at 5°C or below, cover stored food, and eat prepared leftovers promptly rather than eventually. The timelines differ by side of the Atlantic — the US extension suggests eating prepared food within three to four days or freezing it, while the UK FSA advises eating leftovers within two days — so the stricter figure is a good default. Source: OSU Extension, mould on food (opens in a new tab) Source: FSA chill, freeze and defrost (opens in a new tab).
A note on where this framework comes from: the trim-or-toss table is US Department of Agriculture guidance as relayed by university extension services. The FSA does not publish an equivalent cut-and-keep chart — its fact checker's own answer to "can you still eat food if you remove the mouldy part" is no: food that is obviously rotten or mouldy should not be eaten, and while cutting out a significant margin might remove the unseen toxins, there is no guarantee it removes them all — a caution it underlines for vulnerable groups. UK readers who want the stricter rule already have it: when in doubt, throw it out. Source: FSA home food fact checker (opens in a new tab).
And the standing boundary: a Food Says Hi lookup can name the food in a photo — it cannot judge mould depth, smell, or how long anything has been sitting. For the date side of the same decision, use-by and best-before and the leftovers guide cover the numbers; for anything frozen and forgotten, the defrosting guide picks up the next question.
Spotted an error? Tell us — please include the page address and the line that looks wrong.