What you see: An apple with a soft brown area (or areas) on its surface.
What it is: A bruised apple.
Eat or toss: How bruised is the apple? An apple with a rotting and/or moldy bruise should be tossed; a small, shallow bruise can be trimmed and it’s not a big deal to eat it.
Is it OK to eat an apple bruise?
From farm to fruit bowl, apples have lots of opportunities to get bumped and dropped. The result: soft, brown bruises.
So, what does that mean for your healthy snack?
Probably not much. A small, straightforward bruise is not a big deal. You may not like the texture, and we wouldn’t blame you for cutting around it, but it’s unlikely to hurt you.
The soft flesh and brown color are evidence of cellular damage. When an apple bruises, whether from being thrown in a bucket during harvest, riding in a truck with a bad suspension or being batted off a counter by a cat who feels no remorse, its skin doesn’t break, but its cells are weakened. Chemicals normally kept separate within each cell then leak and react with each other and oxygen. This string of chemical reactions leads to the brown color in apple bruises (the reaction is basically the same as what happens when sliced apples turn brown). Biting into an apple with fresh, intact cells yields a juicy snap because your teeth pop open little cellular packets of juice; the diminished cells in a bruised area have lost their pop and leaked their juice.
Simple cellular damage isn’t good for the quality of the apple, but it’s not a food safety concern.
Here’s the caveat: an apple with a bruise is more vulnerable to microorganisms, which are more likely to settle in as time goes by. So eat your bruised apple sooner rather than later.
Bruised apples are more susceptible to decay
While you and I might find an apple bruise unappealing, to a lurking microbe, it’s inviting. Even if the skin hasn’t broken, the damage is enough to lure tiny organisms looking for a shortcut to the fruity buffet under the apple’s skin.
Spoilage bacteria, as in those that decompose the fruit but typically don’t harm people, are usually the first microbes to get to work on an apple. At that point, any squishy, slimy, and/or smelly areas will be clues that they might be doing their worst. While the Centers for Disease Control infrequently links apples to outbreaks of food-borne illness, it’s worth being a little careful around advanced bruises; in the off chance some disease-causing bacteria are in the neighborhood, they could be fortifying themselves in that decomposing tissue.
David Miller, a research professor at Carleton University who focuses on how fungi impact human health, said apple-invading microbes follow a clear order of succession “Bacteria can grow quickly, but the yeasts take over and make enough alcohol to stop them,” he wrote in an email.
Next, he said, the yeasts eat all the simple sugars; when those run out, yeast stops growing. Finally, the slower, but heartier molds get to work decomposing what’s left. Once you see mold, you probably won’t want to eat the apple.
Be careful with moldy apples
A number of common apple molds, most notably Penicillium expansum, produce patulin, a toxin shown to harm organs in animals, according to the World Health Organization. Researchers have also found that it can damage genetic information in cells. The FDA says: “Exposure over time to high levels of patulin may pose a health hazard.”
Patulin is not something you want to ingest.
(Science aside: the Penicillium genus is vast, including both friends and foes. Some species help us make antibiotics, others help us make cheese, and still others, like Penicillium expansum, produce problematic toxins like patulin.)
Public health officials mostly worry about high levels of patulin showing up in processed foods, like apple sauce and juice, where a moldy apple could sneak past quality control and cause widespread contamination that the consumer couldn’t detect. The FDA regulates patulin in processed foods.
But if you’re faced with a patulin-contaminated apple, you’ll probably be so turned off by the apple’s appearance that you won’t want to eat it anyway. An infection with Penicillium expansum starts with soft, watery brown spots. Over time, fuzzy blue mold clumps can show up. Researchers have found that patulin can diffuse at least 1 centimeter into healthy tissue around the wound and that you need to cut at least 2 centimeters around the infection to reduce risk of ingesting patulin.
So, you could trim off moldy areas, with wide margins, and eat it. Miller said he might do that, if desperate. But given the unknowns and potential risks of patulin, not to mention how unappealing the apple would look, he said he’d be most likely to compost the apple and absolutely wouldn’t give any part of it to a child, who would be more vulnerable to a smaller amount of the toxin.
But back to the bruised apples you see in this post, where you see some brown dents, but no watery tissue and no visible mold. What to do?
“I would eat these apples and would cut the bruised area off,” Miller wrote in an email, noting that the bruises are simply exhibiting the oxidative damage we described above.
Why do apples bruise so easily?
Apples are actually full of air! While the exact arrangement varies based on apple type, the fruit’s cells are large and irregularly shaped; they fit together more like a bunch of rocks in a jar, as opposed to stacks of small blocks in a cube. Apples may feel hard and crisp, but that additional space between cells means their flesh more easily gives way after a bump.
(Carrots, by contrast, have small cells with little space between them; this is why you rarely see bruised carrots. It’s also why an apple should never pick a fight with a carrot.)
Apples, already prone to bruising with their airy cell arrangement, become even more vulnerable as they age. Over time, a layer of “glue” between the apple cells dissolves, the air space between the cells further increases and the cell walls become less firm (specifically, enzymes break down strengthening pectin and cellulose). These changes make the apple mealy and more likely to bruise.
Preventing apple bruising
The apple industry is obviously highly incentivized to prevent bruising, which causes major losses every year. Doing so, however, is not as simple as avoiding drops or jostling. The type of apple, the environment it grows in, as well as when and how it’s picked and how it’s stored and transported can all affect the odds of bruising. Here are just some of the steps farmers can take to reduce bruising:
- Monitoring the apple’s nutrient balance. For example, since calcium strengthens cell walls (something we talked about more in this post about a condition called bitter pit), and since potassium and calcium compete with each other, striking the right balance will result in more robust apples.
- Ensuring orchard roads are smooth and free of bumps that could jostle apples .
- Moving apples on trucks with air suspensions. Spring suspensions cause more bruises.
- Not wearing rings when picking apples or holding more than one apple in the hand at once.
- Avoiding picking apples early in the morning, or when they are wet. They absorb some of that moisture, which makes them harder and more likely to bruise. (Kind of like the difference between a full water balloon, which is more likely to pop, and a less full one, which has a bit more elasticity.)
- Using free standing, three-leg ladders as opposed to ladders leaned against the tree. The leaning ladder can injure fruit.
Note to readers: We’d love to include a photo of a moldy apple! If you happen to have one, please send it to [email protected].
- J. David Miller, PhD. Distinguished Research Professor. Carleton University. Helped draft guidelines for mold and dampness published by Health Canada. Co-editor of World Health Organization report, “Mycotoxin Control in Low- and Middle-Income Countries.” Interview and email correspondence Sept. 2022.
- Dr. Macarena Farcuh, PhD. Assistant professor in horticulture. College of Agriculture and Natural Resources. University of Maryland.
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