Why Do Watermelons Explode Sometimes?

Sure, you can get a watermelon to burst by squeezing it with rubber bands, but sometimes this fruit explodes all on its own. Learn how microbes and genetics are responsible in today's episode of BrainStuff, based on this article: https://recipes.howstuffworks.com/exploding-watermelon.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeart Radio, Hey Brainstuff
learned Boga bom Here. A whole watermelon holds a lot
of promise. It's stiff rind contains so many slices of
juicy jewel, bright fruit, fresh flavored and sweet. But it
also contains the potential to begin to split, hiss and

(00:24):
foam and then go bluey, spurting, putred melon guts all
over your picnic. We're not talking about exploding a watermelon
on purpose using the potential energy of stretched rubber bands
squeezing around it. It's possible for watermelons to explode all
on their own or almost because of either genetic factors

(00:45):
or spontaneous fermentation that creates a build up of gases
and pressure inside the rind until it bursts, often dramatically.
For the article this episode is based on How Stuff Works.
Spoke with Walter Reeves, a k A. The Georgia Gardener,
a retired radio until vision host, author and weekly gardening
columnist for our local newspaper, The Atlanta Journal Constitution. He

(01:07):
explained fermentation explosions happen because the watermelon is full of
sugar and a fast growing bacteria or fungus got in
there somehow and is fermenting. Maybe it got poked by
something on the trip home, or maybe it had an
unnoticed blotched disease infection. Basically, some types of the microorganisms
like bacteria and yeasts that live all around us in

(01:29):
our air can eat sugars and poops stuff like ethanol
and carbon dioxide. A reef said, a fermentation causes many
different chemicals to be produced. Some smell of alcohol, some
smell of vinegar, some are floral. Fermentation produces carbon dioxide gas,
which hisses as it comes out of the rind under

(01:49):
slight pressure. So the simple answer is that a watermelon
can ferment inside, and the pressure can cause various effects,
I think, anywhere from the phizzes like crazy sound that
a soda makes when you shake up the can before
you open it, all the way to a mini volcanic
explosion of what Reeves called an ouy, gooey, salimy, yucky

(02:12):
puddle of crapola. A watermelons thick rind usually protects against
this fermenting microorganisms have to have a way to get in.
Maybe the rind was pierced or scratched or weakened with
a bacterial infection. Reeves explained a bacterial blotch disease comes
from infected seed and only affects the rind. It doesn't

(02:34):
spread to the interior, but if the blotch cracks, other
bacteria and fungi can go through the cracks to the
interior of the fruit and begin fermentation. If you find
an infected watermelon with only a small blotch on the rind,
the interior should be fine, but if the interior smells
bad or seems watery, don't eat it. Good advice all around.

(02:56):
But we also mentioned genetics as explained, exploding can be
caused by genetic factors that influence rind thickness, sugary pulp,
and small fruit size. A thin rind plus super sweet pulp,
which readily absorbs water equals boom on a hot day.
It turns out that there's an explosive rind gene that's

(03:17):
found in many heirloom varieties. Its heritability was identified back
in Basically, it causes the fruits rind to burst or
split when it's cut. How stuff works. Also spoke with
Dr Penelope Perkins, vs, a plant physiologist and professor of
horticulture at North Carolina State University. She said, so a

(03:40):
little bump will pop the rind open, and the tiger
pressure in the fruit pushes flesh far and wide. But
this raises a question. If we've known about this explosive
rind gene and can breed it out of watermelons, why
haven't we gotten rid of it? It turns out it's
useful after all. Okay, let's back up a step. In

(04:03):
order to grow a watermelon, the flower of a watermelon
plant has to get pollinated, and in order to grow
a desirable seedless watermelon, that plant has to get pollinated
with pollen from a seeded watermelon plant. So farmers have
to have both kinds of plants flowering, But they don't
want to waste resources actually growing the often less desirable

(04:27):
seeded watermelons. So if they breed their seeded plants to
include that explosive rind gene, the problem kind of takes
care of itself. The melons from these plants either explode
on their own or are easily squished and destroyed. Farmers
even breed them to be small, fruited enough, like palm sized,

(04:47):
so that they won't explode all over the seedless fruit
and make a mess. Today's episode is based on the
article when bad Watermelons Explode on good People on how
stuff works dot com, written by Kerrie tach Row. Brain
Stuff is production of I heart Radio in partnership with
how stuff works dot Com, and it is produced by

(05:08):
Tyler Clang. For more podcasts from my heart Radio, visit
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