Can you eat a bruised banana?
What you see: Brown area on a banana, just below a dark impact wound on its peel.
What it is: A bruise.
Eat or toss? If the peel isn't broken a mild bruise is low-risk to eat, but may not taste good.
A rough bump is all it takes to bruise a banana, leading to a brown impact mark on the peel and, often, below that, a brown spot on the banana flesh.
The brown color can be traced back to natural compounds called polyphenols, which are present in banana flesh, whether it's brown or creamy white. Polyphenols are among the plant’s defenses against everything from too much sunlight to invading microbes, explained Lan-Yen Chang, a PhD candidate studying bananas at the University of Florida.
When the banana's cells are wounded, as happens during bruising, compartments in the cells leak and polyphenols mix with enzymes. Throw in some oxygen and we have a defensive chemical reaction. As Harold McGee writes in On Food and Cooking: The Science and Lore of the Kitchen, had those phenolic compounds been deployed on an insect or microbe, they would have attacked the invader's own enzymes and membranes. To us banana eaters though, the only clue of all that cell-level warfare is the unappealing brown color that those chemical reactions leave behind. You’ve also seen this discoloration in apples, avocados, eggplants and myriad other types of produce.
The brown color alone doesn’t necessarily indicate that anything is unsafe. It’s just evidence that something weakened the banana cells and their defenses kicked in. If you see a brown bruise on the peel, but pristine banana flesh underneath, the damage was restricted to the exterior, so go ahead and eat your banana.
If, however, you see that the white banana flesh has also discolored, as in the banana above, that means the impact hit deeper. In that case, consider:
1. The browning reactions on the banana flesh will likely lead to off flavors because the cellular processes that generate flavor compounds are disrupted, Chang explained. Any flavor changes may or may not bother you.
2. Generally, if the peel remains intact, bacterial or fungal invaders are unlikely to muscle their way to the banana flesh through the weakened cells of a bruise. But if the peel is broken, the impact is especially severe or the wounded banana is so overripe that the peel is very thin and dark brown or black, then the odds go up that opportunistic bacteria and fungi could have settled into the weakened tissue. It's relatively unlikely, but still possible that human pathogens could be among those microbes. Your best bet is to steer clear of those more extreme injuries.
For more everyday bumps like the banana pictured above, Chang’s approach is to trim around any bruises on the banana flesh and to not worry about bruises if the edible portion of the fruit remains pristine.
Is it even a bruise?
Chang notes that the little brown dots that appear on a ripening banana are not injuries, but rather normal peel color changes that occur as the banana ages. Impress your family and friends by calling them "senescent spots."
Lan-Yen Chang. PhD candidate. Postharvest horticultural science. University of Florida.