Is it really that dangerous to eat moldy food?

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When food scientist and writer Joe Rosenthal spoke to former employees of the popular breakfast spot Sqirl and posted their experiences on Instagram, and their anecdotes were musty — literally. These former workers alleged the brunch spot was still using jam that previously had an inches-thick layer of mold growing on top. The story also contained a photograph allegedly taken by a former employee of a “discarded jam mold bucket” that went extremely viral. I warn you, the image is not for the faint of heart or the gentle of stomach.

Since the photos emerged, Sqirl has acknowledged its fungal faults, and promised to use more stringent storage methods. Still, a spore on my consciousness has blossomed: How was a popular spot like this able to operate for so long without anyone either getting sick? Food that has grown mold is unsafe to eat, right? Well, it’s complicated.

About the dangerous molds

Not all molds are created equal, friends. “Some molds create mycotoxins — a poisonous substance that can make you sick — that are poisonous to people,” says Janilyn Hutchings, a food scientist and certified food safety professional at State Food Safety. Mostly, we're talking food poisoning. But the worst of these is aflatoxin, which has been shown to cause cancer, she tells Mic. “In addition, finding mold on one food can be a less serious problem than finding mold on another.” Indeed, not all molds are toxic, as we know from the copious amounts of gorgonzola some of us are wont to consume.

One of the reasons why the bad molds are so dangerous to humans is because of how it grows. Science Insider released a video explaining the process in great detail, but here are the broad strokes: All molds, including the kind you typically see growing on food, has a part that you can see, and also a microscopic part that you can’t see.

The video uses a great analogy of mushrooms growing in a forest. The part we humans can see (the caps that grow above ground) are actually joined by an underground network of microscopic roots called hyphae. That’s why even if you remove the mold from that ciabatta bread you want to chomp into, the mold’s roots that you can’t see could still be hanging out in the rest of it.

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According to the USDA, the mold in jams and jellies could produce a mycotoxin and so should be discarded at the first sight of mold, but there are other foods like cheese, salami, and certain vegetables that are safe to consume once you remove the mold. Fermented foods that are made with healthy microorganisms specifically introduced to a fresh food to improve shelf life are a different beast entirely — but they, too, can also grow mold. To the layperson, this is slightly confusing, but there are easy considerations (and google!) to keep yourself safe.

“One big reason why some mold is ‘scrapable’ and the item is still edible is because [some] food items are more firm and prevent mold from spreading, versus other softer food items that allow mold to spread easily,” Amanda A. Kostro Miller, a Chicago-based dietician and nutritionist tells Mic. “Mold grows and spreads by penetrating a food item. So, harder or firmer foods will be more resistant to mold penetration, whereas soft and liquidy foods will not be able to keep out mold penetration.”

Why harder foods are less susceptible to mold

One of the most salient things to consider when you’re thinking of whether to chuck something that has a telltale mold spot is to determine whether it’s hard or soft. Hard foods, like parmesan cheese and certain firmer veggies and fruits are denser and therefore harder to penetrate by mold, according to the USDA’s guidelines. An analogy for you: Mushrooms have an easier time growing in soft, wet soil than on top of rock formations.

Similarly, the aforementioned meats like ham or salami, which have been made less moist by being cured or dried, are still safe to eat, even if you see a little mold on the surface. That white stuff you see encasing salami, is called penicillium nalgiovense and is actually used to protect the meat from unsafe molds as it cures. Science is fascinating, isn’t it? While likely that mold hasn’t taken deep roots, don’t chomp down on that before you remove the mold and cook it. “Also, make sure that you don’t touch your knife to the mold and then cut the food in other parts, otherwise you will just spread the mold around the food as you cut,” Miller adds.

When it comes to bad mold on soft foods (where it thrives, to reiterate), Hutchings says that the roots — the part the human eye can’t actually see — are the most dangerous part of mold. So even if you remove what you can see, you might end up consuming toxins anyway. “Whenever you find mold on foods that aren't shelf-stable or have a high moisture content, like meal leftovers, jams, and dairy products, it's likely the mold roots and spores have already penetrated the item,” she says.

Hutchings suggests that food items with higher-moisture like hotdogs and lunch meat and foods made from or containing grains and nuts are also particularly susceptible to mold and the safest thing to do is toss the entire product when you see a spot. Use common sense: If the entire item is bruised, softened and moldy, throw it out. If the item was not properly processed, cooked or stored and has mold, throw that out. “If you catch mold on a firm fruit early, store it correctly and cut around it with plenty of margin,” she adds.

On the glorious, good molds

So back to the stinky beloved cheeses. Yes, there are exceptions to the hard (and soft) rules of mold consumption. Blue cheese, in addition to being one of the healthier cheeses out there, is made by "safe molds'' which are involved in the manufacturing process of some cheeses, including roquefort, gorgonzola, and brie. Another type of food: huitlacoche or corn smut (feel free to giggle, I did) is a type of fungus that grows on corn and is a rare delicacy in South America and elsewhere. I can tell you from experience that corn smut is beyond delicious, but even though I’ve eaten it, I still recoil at its fungal image.

“Blue cheese is safe because the mold used to make it is part of the manufacturing process. As for corn smut, it's important to understand one thing — all molds are fungi, but not all fungi are mold. Huitlacoche is a different type of fungi that's more similar to a mushroom than a mold, and it just so happens to be an edible mushroom,” Hutchings says. It all comes down to this: If a spot of mold makes you uncomfortable, just do what I do. Skip the hungry desperate deliberation and order takeout.