Molds on Foods: Food Safety
Most of us have opened the fridge or bread bin and found something furry. Is it safe to cut the mould off and eat the rest, or should it all go in the bin? The answer depends on the food. Here is what mould is, why some mouldy food is risky and what to do with the most common culprits.
What is mould?
Moulds are microscopic fungi. The fuzzy patch you see on the surface is only part of the story: many moulds send thread-like roots deep into food, where you cannot see them. Moulds thrive in warm, damp conditions, which is why bread, soft fruit and leftovers can turn mouldy so quickly.
Why mouldy food can be harmful
Some moulds can cause allergic reactions or breathing problems, and some produce poisonous substances called mycotoxins. One group, aflatoxins, has been linked to serious illness with long-term exposure. You cannot tell by looking whether a mould is harmful, so the safest approach is to treat unexpected mould on food with caution. Do not sniff mouldy food, as breathing in spores can cause problems for some people.
Some moulds are deliberately used in food, such as the blue veins in Stilton or the white rind on Brie. These are safe to eat.
What to keep and what to throw away
The general principle is that mould spreads easily through soft, moist or porous foods, but struggles to penetrate hard, dense ones. The US Department of Agriculture’s guidance is a widely used reference.
| Food | What to do | Why |
|---|---|---|
| Bread and baked goods | Throw away | Mould spreads below the surface |
| Soft cheese, yoghurt, soured cream | Throw away | Moist foods let mould spread unseen |
| Soft fruit and vegetables, such as berries, tomatoes, peaches | Throw away | High moisture, mould spreads quickly |
| Jams and jellies | Throw away | Mould can produce toxins |
| Cooked leftovers, meats, pasta, grains | Throw away | Soft and moist, may also carry bacteria |
| Hard cheese (not mould-ripened) | Cut off at least 2.5cm (1 inch) around and below the mould | Mould struggles to penetrate dense cheese |
| Firm fruit and veg, such as carrots, cabbage, peppers | Cut off at least 2.5cm around and below the mould | Dense texture limits spread |
When cutting, keep the knife out of the mould itself so you do not spread it, and rewrap the food in fresh wrapping. If in doubt, throw it out.
How to stop food going mouldy
- Keep your fridge at 5°C or below, as the Food Standards Agency recommends.
- Cover and chill leftovers within about two hours, and eat them within two days.
- Store bread in a cool, dry place, or freeze it if you will not eat it quickly.
- Clean the fridge regularly, including the seals, and wipe up spills.
- Check use-by dates and use older food first.
- Do not buy more soft fruit than you will eat in a few days.
Frequently asked questions
What if I accidentally eat mouldy bread?
Most people who eat a small amount of mouldy food by accident do not become ill. If you feel unwell afterwards, or have a mould allergy, breathing problems or a weakened immune system, contact NHS 111 or your GP for advice.
Is the white coating on salami mould?
Some dry-cured salamis have a white coating of mould that is part of the curing process and safe. Any other unexpected mould on cured meats is a sign to be cautious, and the product should usually be discarded.
Where to go next
Good hygiene starts with clean hands. Read about the importance of handwashing in food preparation.
