Q. Can you still eat food once you chop the mould off?
A. It is risky to eat food that is already contaminated with visible mould. As mould grows it tends to produce by-products (secondary metabolites) that permeate into the food or material it is growing on. Some strains of moulds such as those belonging to Aspergillus, Penicillium and Fusarium produce metabolites that are highly toxic.
Q. If there are foods you can eat after chopping mould off, what are they?
A. I would not recommend eating of any food that has previously been contaminated with mould because the person eating the food may not be knowing which mould is contaminating the food and whether the mould has produced toxins.
Q. What kind of moulds are unsafe to eat? Why?
A. All moulds are generally unsafe to eat. However, the risk is higher if one is to eat those moulds known to produce toxins (the so called toxigenic moulds). Some examples of toxigenic moulds commonly found on food are species of Aspergillus, Penicillium and Fusarium. Some species of these moulds are known to produce highly toxic metabolites. A good example is Aspergillus flavus which produces Aflatoxin. Recently aflatoxin killed 125 people in Kenya after eating contaminated maize.
Q. What are the conditions that are best for producing the toxins in toxigenic moulds?
A. The conditions that trigger toxin production by moulds are not well understood. However, genetic and growth conditions are known to influence toxin production. Growth conditions that may influence toxins production are food nutrient composition, pH of the food, moisture content and temperature.
Q. If mould is present on food, does this necessarily mean that bacteria causing food poisoning is also present?
A. If mould is present on food, this does not necessarily mean that bacteria causing food poisoning are also present.
Q. What are some of the symptoms that can be caused by eating toxigenic moulds? Are any fatal?
A. Symptoms of mycotoxin poisoning may depend on the root of entry into the body.
Inhalation symptoms may include: nose and throat pain, nasal discharge, itching and sneezing, cough, wheezing, difficult breathing, chest pain and bloody sputum.
Ingestion symptoms may include: nausea, vomiting, and watery or bloody diarrhea with abdominal pain.
Contact Symptoms: burning skin pain, redness, and blurred vision (if the eyes are affected).
Severe poisoning can lead to death. Some Mycotoxins such Aflatoxin can also trigger cancer.
Q. Are there any ‘safe’ moulds that you can eat? Are there any moulds that may improve health by eating them?
A. There are no ‘safe’ moulds to eat. However, some moulds including some that are known to produce toxins have been used for many years in production of fermented food. Quorn is a high protein fungal product produced from a species of Fusarium. It is used as an alternative to animal protein.
Q. Can you mistake bacteria for mould? ie. do any look similar to the naked eye?
A. Bacteria and moulds are totally different organisms. Their cell structures are different. Their mode of growth is different and therefore easy to differentiate.
*Jackson Kung'u, Indoor Mould & Bacteria
So as far as mouldy cheese goes: If a piece of cheese has mold on it, should I throw the cheese away or can I cut off the moldy part and eat the rest of it?
The answer depends on the type of cheese. Moulds are microscopic organisms that have thread-like roots that burrow into the foods they grow on. Most moulds are harmless. Moulds are even used to make some kinds of cheese, such as Roquefort, Gorgonzola, brie and Camembert. These moulds are safe to eat.
But mould on cheese that's not part of the manufacturing process can also harbor harmful bacteria, such as listeria, brucella, salmonella and E. coli. With hard and semisoft cheese, you can cut away the mouldy part and eat the rest of the cheese. But soft cheeses should be discarded.
Mouldy cheese? What to do:
Hard Cheddar, Colby, Swiss, Parmesan, Romano, Gruyere Safe to eat if the mould is removed. Cut off at least one inch around and below the mould spot. Keep the knife out of the mould itself so that it doesn't cross-contaminate other parts of the cheese. Cover the cheese in fresh wrap.
Semisoft American, Asiago, baby Swiss, Monterey Jack, mozzarella, Muenster, Gorgonzola Safe to eat if the mould is removed. Cut off at least one inch around and below the mould spot. Keep the knife out of the mould itself so that it doesn't cross-contaminate other parts of the cheese. Cover the cheese in fresh wrap.
Soft Brie, blue cheese, Camembert, cottage cheese, Neufchatel, feta, ricotta, shredded and sliced cheeses Discard the cheese.
Source: U.S. Department of Agriculture, 2006
Dangers that lurk in your fridge
Ever been blown away by foul-smelling, mould-growing leftovers when you open your fridge?
Urgh. Time for a clean-up. But before you park the rubbish bin in front of the fridge, find out what you can keep and what you should definitely throw away.
There's no need to worry too much about the mouldy patch on that block of Cheddar cheese. If you're not too grossed out about it, you can simply cut off the mouldy section and still enjoy the rest of the cheese.
But if the cheese is actually covered in mouldy patches, it's probably best to just cut your losses, chuck it in the bin and add "cheese" to your shopping list. The same goes for firm fruits, vegetables and hard salami.
However, if mould has grown on other foods, such as luncheon meats, leftover meat and poultry, cooked pasta, casseroles, soft cheese, yoghurt, jams, bread or nuts, it's time to say goodbye.
Some moulds may cause allergic reactions and respiratory problems (that's why it's never a good idea to sniff mouldy foods). In the right conditions, a few moulds also produce so-called “mycotoxins” – poisonous substances that can make you sick. It's hard to tell just by looking at a mould whether it has produced toxins or not.
When a food shows heavy mould growth, chances are that the roots of the mould have penetrated the food deeply. More allergy-causing moulds could be present than meets the eye and it might be unsafe to eat.
Also, if dangerous toxins are indeed present, chances are that they've spread throughout the food. It's difficult for mould to penetrate dense foods – that's why hard cheese, hard salami and firm fruits and vegetables are generally safer.
Sour milk and yoghurt
It's pretty easy to tell when milk has gone sour: simply sniff at it. Another tell-tale sign is little flakes floating around in it.
While the pungent smell and the changed consistency is good enough reason for most people to ditch the milk, you might be wondering whether it's still okay to use.
If milk is a day or two past its sell-by date, it can still be safely consumed and it can still be used in milk-based recipes, such as pancakes. But as soon as you get that sour smell, it's better to just throw it away. Milk is just such an ideal growth medium for dangerous bacteria that one can never be too safe.
Also, if a yoghurt tub hasn't been opened, yoghurt past its sell-by date might also still be safe to eat. Note, however, that the yoghurt will gradually start to lose flavour, texture and nutrients. Eventually, it might also become unsafe to eat.
So, if it's one or two days past the sell-by date, have a go at it. But if it starts pushing a week or two, chuck the yoghurt in the bin. You'll be better off buying a fresh tub or two.
You bought the fillet of kingklip, but just haven't had time to eat it. Is it still okay?
Fresh, uncooked fish is only good for one or two days in the fridge. If it's cooked, it should be okay for three to four days, but only if you heat it thoroughly before eating it.
But what if you can't remember when you bought it?
Well, then it's probably a good idea to get rid of the fish anyway. But if you need more confirmation, a strong "fishy" odour in your fridge is a tell-tale sign that fish has gone off.
Here's the important thing: meat might still look, smell and even taste fine, but it doesn't mean that it's safe to eat.
Always check expiry dates and don't use raw minced meat that's been in the fridge for more than two days and steaks or chops that have been in there for more than four. If the minced meat has been cooked, it should be okay for about four days.
If you can detect a slime layer on luncheon meat, if meat has an odour or has changed colour, it's a definite no-no. But long before these changes occur, the meat might already be shaky.
At last, some good news: fruit and veggies that aren't in a perfect, plump condition any more can still be used.
The best is to use the fruit/vegetables in cooked food, such as stews, soup or "potjiekos". The greens have merely lost their shape as a result of dehydration and natural enzymatic ageing.
By the time fruit and vegetables pose a health risk – in other words, when dangerous bacteria are present or when there's substantial mould growth – you wouldn't be keen to eat them anyway. - (Carine van Rooyen, updated November 2007)
- Canadian Partnership for Consumer Food Safety Education (www.canfightbac.org)