So some cheeses seem to be toxic for you if you eat them when they have mold on them, while others are mainly being consumed when they get moldy. Why is it so that some types of cheese will make you sick, while you can eat others without a problem?
In: Chemistry
Short version: The mold that grows on Bleu Cheese is a very very specific species of mold that isn’t toxic to humans.
But if you leave it any food out for too long (cheese or any food, really), some random wild mold floating through the air will land on the food and start growing.
This wild mold is not the safe species from bleu, so it can be toxic to humans.
The same reason that you can eat mushrooms but no death caps. Both are fungus. The mold on cheese is also a fungus. Some of them are delicious some are deadly. Many centuries ago people found out which molds are mit Dangerous and they saw, that If theese molds grow on their food it prevented other molds from growing. So the food was longer edible by adding the right Kind of mold.
Most molds that grow on non intentionally moldy cheese is non toxic aspergillus or penicillin molds. I usually just cut or scrape it off.
There are many types of mold (aka fungus) that can grow on cheese, some types of mold are harmless while others can be toxic. In the cheese making process, the cheesemakers can tightly control the environmental conditions and encourage the correct type of mold to grow. If you get mold on a cheese that isn’t meant to me moldy, it could be any type of fungus and potentially a harmful one.
The type of mould that makes a blue cheese blue is different from the type of mould you will find in a lump of Gouda left in your fridge for too long.
Some mushrooms are safe to eat, while others are hugely dangerous and will kill you if you eat them – mould is the same. Blue cheese is made in such a way as to grow certain types of good mould, while the stuff that appears naturally in your fridge is the bad stuff that can make you ill.
It depends on the type of mold. Different molds produce different waste products. The waste produced by the mold in blue cheese isn’t toxic to us. The waste created by other types of mold are toxic to us.
So it’s not necessarily the cheese itself that makes you sick, rather the properties of the cheese and the types of mold growing.
Mold spores are all around us and on our food. When a mold spore lands on food it starts to grow little microscopic filaments called mycelia. These are sort of like roots. For very hard cheeses, these roots can’t really penetrate into the cheese that well, so in general you can cut the mold away and eat the cheese with little worry of ingesting any mold. In the case of soft cheese, the roots are able to penetrate much deeper into the cheese and often will remain present in the cheese even if you cut away the visible mold.
Blue cheese – and other cheeses that are sold moldy – is a special example of cheese that you can eat moldy. In the cheese making process, a particular type of mold ([Penicillium roqueforti – a close member to the mold we use to make penicillin](https://www.reddit.com/r/explainlikeimfive/comments/lgxvz8/eli5_why_can_you_eat_some_types_of_cheese_with/gmuapyb/)) is introduced into the cheese which is safe to eat. This mold actually changes the texture of the cheese as well, making it more creamy. Importantly, the cheese makers also keep a close eye on the cheese during this process to make sure no dangerous molds are growing. Keep in mind, however, that even though it’s safe to eat the mold in blue cheese, you should keep an eye out for any new smells or colors in cheese that’s been in your fridge for too long because that can indicate the presence of harmful molds taking over which may make you sick through the [toxins](https://www.reddit.com/r/explainlikeimfive/comments/lgxvz8/eli5_why_can_you_eat_some_types_of_cheese_with/gmu543d/) they release.
Edit: Typos, and a couple of links to other comments for more info.
Edit 2: Since I only briefly said in the last sentence and didn’t explicitly state/people aren’t reading the linked comment: Some molds produce dangerous/toxic byproducts into its surroundings that make us sick when eaten, whereas others do not and are fine to consume. Because you won’t know the type of mold growing on your cheese or whether its harmful it can be dangerous to eat moldy cheese that isn’t sold moldy.
It’s the milk, from which cheese is made that can be a problem. Raw (unpasteurized) milk can carry Listeria, Brucella, Salmonella and other seriously bad bacteria. Pasteurizing the milk kills those germs. Any cheese made from unpasteurized milk might be risky, visible mold or not.
Mold that grows on cheese usually is not toxic. Blue mold is usually from the Penicillum family (penicillin was the very first antibiotic used on humans). Some molds and bacteria are used to make and/or flavor cheese. For instance, Camembert and Brie uses Penicillum camberti (a bacteria, not a mold) and often they have a coating of white surface molds that is harmless and many find it yummy.
Rules of thumb. Crumbled or soft cheese (Gouda is a semi-soft cheese) that shows abnormal mold (blue mold on blue cheese is just fine) should be tossed. Mold on hard cheeses should be cut away, about 1” deep and 1” all around. Mold has trouble growing deep into hard cheese, but easily into soft or semi-soft cheese. Black mold on any cheese should be tossed for it could be Aspergillus niger, a toxic mold.
A related subject about which molds that grow on compressed tea “designed” for storage are dangerous keeps going over a similar issue. All of those molds are seen as a bad thing, but one common take is that you can brush off a white mold version but anything green or yellow is more dangerous, and you need to throw that “cake” (bing, or disk) away. The other take is that the mold is growing inside the tea too, and even white mold is dangerous, and you should throw the tea away (pu’er, that type).
A type of yellow mold is actually seen as positive in other hei cha (a broader compressed tea category), and is intentionally inoculated. In all these cases the molds aren’t regarded as a poison that will kill you, like cyanide, but are toxic, and cause health problems in other ways, including being carcinogenic, or potentially damaging internal organs. Except for that “good” yellow mold; that is said to have no negative effect.
Mold is a type of fungus – a group which includes mushrooms.
Just as some mushrooms are delicious and others may harm you, some mold improves a cheese and some mold may make you sick.
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