A perfectly ripe pineapple can be a hassle to find and carve, but once you're down to those golden rings, you've got a perfect summer companion. From piña coladas to pizza, the juicy hunks can be hard to quit — until the inside of your mouth begins to feel weirdly raw.
If one too many bites of pineapple leave you with a tingly tongue, burning cheeks or a desperate desire to scratch the inside of your mouth, you aren't alone. The culprit is likely an enzyme complex called bromelain, according to a 2019 letter in the journal Annals of Allergy, Asthma and Immunology (opens in new tab). Bromelain is a protease — a type of enzyme that breaks down proteins into their building blocks, known as amino acids — that's unique to pineapples, which is why pineapples are also excellent meat tenderizers.
"At the moment, there isn't a lot of evidence about the palatability of bromelain," or the way the enzyme tastes and feels in your mouth, said Alessandro Colletti, a pharmacologist who studies bromelain at the University of Turin in Italy. But it's possible that after eating several pieces of pineapple, you'll begin to feel the bromelain breaking down some of the mucin proteins that make up the protective mucosal layer in your mouth.
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So, if you dive into a fruit salad, is it possible that eating too much pineapple will do you harm? It's doubtful, Colletti said. He noted that bromelain isn't dangerous to humans (though it is an effective defense (opens in new tab) against pests that would damage the pineapple plant). "When you eat pineapple, the concentration of bromelain is about 500 micrograms per milliliter," he said. "So the concentration is not really high." It's even safe at much higher concentrations. For instance, bromelain oral gel, which has a concentration 200 to 400 times greater than fresh pineapple, can be applied directly to the mouth because its anti-inflammatory properties can offset mouth sores caused by chemotherapy, Colletti said.
Moreover, your mouth quickly begins to replace any of the cells damaged by bromelain to prevent any permanent damage or change by the pineapple's proteases, according to reports by Bon Appétit (opens in new tab).
Other tropical fruits, such as papaya, have similar proteases but don't leave a raw feeling in the mouth. The acidic nature of pineapple may be partly to blame for its weird effect, Paul Takhistov, an associate professor of food engineering at Rutgers, the State University of New Jersey, told Self (opens in new tab). Pineapples typically fall between 3 and 4 on the pH scale (a score of 7 is neutral), according to Healthline (opens in new tab). Takhistov hypothesized that bromelain dissolves some of the mucin proteins in the mouth, which makes your mouth more sensitive to irritation by the pineapple's acidity. It's actually the two together, the acidity and the enzyme, that likely make your mouth sore, he said. Colletti added that bromelain itself can have an acidic flavor, which might add to the acidic experience.
As for how to bypass the tingling, in one episode of Netflix's Ugly Delicious (opens in new tab), a man in Mexico tells Danish chef René Redzepi to soak the peeled pineapple in saltwater. However, there isn't much scientific evidence to back this up. You can also grill the pineapple or heat-treat it in some other way, as heat deactivates enzymes, Bon Appétit reported.
And if you want to get the benefits of bromelain, such as its antioxidant properties, Colletti said taking a supplement is best. That way you get higher concentrations of bromelain without all the sugar that makes pineapple so sweet.
Originally published on Live Science.