- If your bread is moldy, it is safest to throw out the whole loaf since mould’s roots can spread undetected to the naked eye.
- While most molds aren’t dangerous to consume, some produce toxic byproducts called mycotoxins. Others can cause allergic reactions like coughing, sneezing, and vomiting.
- Storing your bread in a cool, dry environment like the refrigerator will help ward off mould growth.
- This article was medically reviewed by Tania Elliott, MD, who specialises in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
- Visit Insider’s Health Reference library for more advice.
It’s a common scene: You’re heading for the toaster with your last slice of bread when you notice the telltale furry green spots of mould.
While you may be tempted to scrape the splotch off and eat your breakfast anyways, it’s better to be safe than sorry. Mould can not only spur an allergic reaction, it may also make you sick.
Mould spores are everywhere
Mould is a type of fungus that lives on plants or animals. Under a microscope, it looks like a clump of mushrooms.
The stalks, or sporangiophores, are attached to roots that dig deeper into soft foods, like bread, as they grow. Atop the stalks are sporangia, which generate spores that launch into the air and float to a new host to reproduce.
“Every time a consumer opens up a loaf of bread, they potentially introduce mould spores. If there is a mycogenic fungi in the house, it could land on the bread and start to grow,” says Randy Worobo, a professor of food microbiology at Cornell University.
So basically, mould spores are everywhere. However, many aren’t dangerous to consume. In fact, some varieties are used to make foods like cheeses, such as Brie and blue-veined Stilton. Yet, it’s nearly impossible for the average person to determine if that fuzzy mould is dangerous or safe to consume.
“If it’s a mould and you find it on your food, and it wasn’t put there by the manufacturer, you have to assume it’s not OK,” says Donald W. Schaffner, a professor of food science at Rutgers University.
Mould is a potentially dangerous fungus
Some molds produce toxic byproducts called mycotoxins. These poisonous substances primarily affect grain and nut crops like wheat and peanuts. One of these, aflatoxin, is associated with cancer.
A mould’s genome, combined with the environment in which it grows, determines whether it makes toxins or not, Schaffner says, adding that “what makes a mould a toxin in one environment may not affect it in another.”
Thankfully, it’s less common for the most prevalent bread mould, Penicillium, to produce mycotoxins. But it can happen in rare cases, which is why it’s best to be safe than sorry.
Mould spores will also sometimes produce proteins that cause an allergic reaction that can cause coughing, itchy eyes, or an asthma attack. However, if you don’t have mould allergies, you are not likely to become seriously ill if you accidentally consume it.
Yet, people with compromised immune systems, like those undergoing cancer treatment or with an immune disorder, could be at higher risk for a fungal infection, Worobo says. Call your doctor if you accidentally consumed mould and are experiencing symptoms like nausea or vomiting.
Toss most foods at the first signs of mould
Simply cutting off the moldy bits of bread isn’t enough to ensure safety because of those pesky roots that grow deep into the food. And thanks to those airborne spores, it’s likely that the rest of the loaf is infected too.
So, if you find mould sprouting on your bread, discard the whole loaf in a sealed container, and – for good measure – clean the area it was stored with soap and a fresh rag or sponge.
Mould grows and spreads more easily on soft foods like deli meat, cheese, and fruit. So, you should discard these foods at the first signs of the telltale fuzz. The same goes for pet food, as our furry friends are just as likely to get sick as us when they eat moldy pet food (or your dinner leftovers).
However, there are exceptions to the discard-when-moldy rule: dry-cured salami and hams typically have a thin layer of surface mould when you purchase them that can be consumed or scraped away.
Meanwhile, mould on hard cheeses like parmesan, or firm vegetables like cabbage and carrots, can be trimmed away. That’s because the mould’s roots struggle to pierce through denser foods. Just make sure your incision is at least an inch around the mould, being careful not to contaminate the knife.
Be aware, though, that tinkering with moldy food can cause spores to become airborne, potentially infecting fungus-free fare. “If you have a fresh loaf of bread on the counter and take moldy bread out of a package right next to it, you’re risking contamination,” Worobo says.
That goes for any moldy food, whether it’s bread, cheese, cabbage, or those leftovers your dog is eyeing greedily. They all have pesky spores that can contaminate your kitchen. That’s why, when dealing with mould it’s best to discard the food in a sealed bag or wrapped in plastic.
Refrigerate your bread to keep mould away
Store-bought bread will generally stay fresh for a couple of weeks if stored in the pantry, and up to three weeks in the refrigerator. Whereas, homemade loaves will only keep for three to five days in the pantry.
Store-bought bread lasts longer because it typically includes preservatives like calcium propionate or sodium propionate that inhibit mould growth. These are regulated by the FDA and have a long history of safe use.
Mould spores germinate – or grow – more rapidly in warm, moist environments. To keep them at bay, store bread in a cool, dry area, and clean your pantry and fridge frequently.
If you have more bread than you think you can eat in a couple of weeks, then Schaffner recommends slicing and storing it in the freezer. The extremely cold temperature will prevent spores from germinating and keep your loaf mould-free indefinitely.
For a look at why you should never eat the clean part of moldy bread, check out the video below: