You may have heard that you shouldn’t throw rice at weddings because it’s bad for birds.
Because they will eat it and it will expand in their stomachs and hurt them or even make
them explode.
Fortunately, it takes more than a few grains to stop these tiny dinosaurs, and we can demonstrate
why...with chemistry.
This myth seems to go back to at least the 1980s, including a law introduced in the Connecticut
state legislature attempting to ban rice at weddings as well as an advice column by Ann
Landers.
The fear is that rice will expand in the innards of our feathered friends the way it does when
you cook it on the stove.
It draws in more and more water until -- pop!
Rice expands because it contains these starch granules.
Starch has lots of water-loving hydroxyl groups.
And it’s packed up tightly inside those granules.
As water drifts in, it sticks to the starch, forcing the tightly packed starch molecules
to spread out and the starch granules to swell.
That makes the whole rice grain expand.
But!
There are a few differences between a bird and your faithful rice cooker.
A bird’s digestive system is breaking down food for energy.
Birds’ internal plumbing is a little different than ours.
Technically they have a crop, not a stomach, which is the organ we’re worried about in
cases of hypothetical rice rupture.
Your rice cooker cooks rice in less than an hour in your kitchen, but that’s thanks
to the heat.
At a bird’s body temperature of around 102 Fahrenheit, it might take around four hours
for rice to swell fully.
And in that amount of time, it’s also being broken down and digested.
It doesn’t just sit there and wait patiently for its chance to blow up the bird.
We tried it at room temperature, or, well, a bit lower than room temperature in our chilly
studio.
I combined the rice with room temperature water at a volume ratio of three to one so
that there would be plenty of water to absorb and let the rice get big and fluffy.
But even leaving the rice overnight -- from about 4 pm to 11 am -- didn’t result in
much of an expansion of the grains at the temperature we had to work with.
From this single, statistically non-rigorous trial, we didn’t get rice to passively expand
very much at all — but hold onto that thought.
Rice is a type of grain that some wild birds rely on as a food source.
If it was dangerous, we’d see those birds dropping out of the sky all the time.
Other seeds -- which birds eat -- expand too, by a similar amount to rice.
We bought some white millet birdseed, and a variety of grains and grain-like things
— I think some of these are technically pulses — lentils, beans, and pearl barley.
We used the same volume of both grains and water for each trial, and left them for the
same overnight interval as our rice, and...well, the millet floated, so it’s hard to say.
But our other options expanded dramatically more than the rice did at the same temperature!
Which might lead you to conclude that if rice is a bird guts explosion risk, so is every
other kind of seed they might conceivably want to eat.
We’re basing this demonstration on a 2005 paper in The American Biology Teacher by Dr.
Jim Krupa, who found that instant rice expands WAY more than regular rice under the conditions
you might find in a bird’s digestive system.
So if regular rice can’t explode a bird, could instant?
We started with equal volumes of plain white and instant rice in an equal volume of water.
We got the same result -- instant rice expands like crazy.
We couldn’t find a definitive answer as to why instant rice expands more than regular
rice, but we’re guessing it’s because it has already been cooked and dried out again.
The cooking process doesn’t just draw in water.
It also starts to rupture the structure of the rice grains, as well as expand cracks
that were created during the milling process.
So when you cook the rice a second time, there’s probably even more room for water to creep
in and expand.
I’m guessing that’s also why it floated -- those cracks were filled with air until
they soaked up water!
Does that mean instant rice is dangerous?
Well, birds don’t seem to like it very much.
Dr. Krupa fed both to his pet birds, and they picked plain rice over instant.
But even when the birds did eat instant rice, it didn’t seem to hurt them.
Plus, nobody’s buying instant rice to throw at weddings, because that stuff’s expensive.
If you want to be super safe, throw regular rice.
Super safe for birds, I mean.
The concern is admirable, but it’s not backed up by the science.
Also... isn’t all that rice kind of a slip hazard?
Is something I learned when I dropped the box of instant rice and spilled it all over
the studio floor.
Whoops.
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