The Case of the Man-Eating Pineapple

Reader Brandi writes in to ask why her recent attempt to make a fresh pineapple JELL-O ring ended in disaster. Brandi, the answer is that fresh pineapple contains an enzyme by the name of bromelain which is a protein-digesting enzyme, and gelatin is a protein. Canned pineapple will work in a JELL-O mold because the heat of the canning process denatures (chemistry talk for “messes up”) the bromelain enzymes.

I know what you’re thinking. Or at any rate I know what you might be thinking. Oh hell who am I kidding, you’re almost certainly not thinking it but I needed a transition. What on earth is a protein-digesting enzyme doing in a pineapple? It’s a good question, because really, what use does a fruit have for such a thing?

The answer is that nobody really knows. One theory is that late at night when nobody’s looking, pineapples nip out to burger joints to take advantage of off-hour discounts. Another holds that the enzyme is a defense mechanism designed to kill insects that eat pineapples. Yet another posits that bromelain irritates the stomachs of animals that eat pineapples. Not enough to deter the animal completely, since fruiting plants rely on animals to spread their seeds, but enough to discourage any single one from make a pig of itself at the buffet.

There is one other very interesting idea on the subject, specifically that fruit proteases (protein enzymes) are an example of cooperative relationships between plants an animals. How so? Because proteases, when they pass into the digestive system of an animal, kill and dissolve parasites like tapeworms. And that of course is a considerable benefit for any omnivore whose insurance doesn’t cover gastrointestinal disorders. But that’s really just a guess. In truth the mystery of the meat-digesting fruit has yet to be solved.

6 thoughts on “The Case of the Man-Eating Pineapple”

  1. I would posit that such an enzyme isn’t meant as a deterrent for bugs directly, but instead is meant to ward off (i.e. kill and eat) any spawn/eggs left behind by a visiting bug. That particularly would keep such nasties from killing off a pineapple fruit before it ripened, thus permitting the spread of seeds.

    Either that, or God has a REALLY weird sense of humor.

    1. I lean toward the latter explanation, but the former is also excellent…something I’d never have considered. Thanks, Roger!

      – Joe

  2. I’m sure we have discussed proteases before, but just in case the jello-makers want to try other fruit, you can’t use kiwi fruit or papaya either. They contain actinidin and papain respectively, both of which are great meat tenderisers and gelatin dissolvers. Slices of kiwi fruit placed on top of bowls of jelly (jello in the US) used to be a favourite science festival demo. They makes lovely holes and sink.

  3. In the catering kitchen where I work someone decided it would be great to put chopped fresh pineapple on grilled slices of ham for holiday dinner deliveries. Some was left over and the next day, since I love ham, I decided to try it. Absolutely horrible. The texture of the ham was disgusting.

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