Maaria
Hey what’s up guys? Today I’m asking you, have you ever wondered why onions make you cry? Thanks to Farfan for the question and get ready for some science all up in your face. The onion or Allium cepa, is used all over the world to make delicious dishes. They’re also quite handy for science experiments as their cells are quite big. So you can see them under low magnifications. They’re also a handy analogy for ogres, but what is it that gets the tears flowing?
Onions absorb lots of things from the soil, including sulphur, which they store in their cells to make amino acids. They also contain enzymes alliinase and lachrymatory factor synthase, let’s call this LFS. Cutting through onions destroys these cells and releases all the contents into the air. When alliinase is released into the air, it converts amino acid sulphoxides into sulphenic acid. This is then converted into the volatile sulphur compound propanethial-S-oxide by LFS. Let’s call this PSO. This gas reacts to the tears in your eyes to form sulphuric acid. Yep, that’s the same stuff as battery acid.
But wait, I don’t usually cry before I cut onions unless I’ve been watching something sad like the Bridge to Terabithia. Seriously, that is a kids film.
Your eyes constantly produce tears called Basal tears to keep them lubricated. When they come into contact with an irritant, they produce Reflexive tears, which flush out the eye and get rid of the irritant. So what can we do to stop this catastrophe from happening every time we want to make a curry? What up stereotypes? But seriously, it’s the only thing I can think of. And now I really want a curry.
Well, so far the jury’s out on getting rid of these pesky enzymes altogether by breeding them out. LFS the enzyme, which produces the irritant PSO, which makes you cry, was discovered in 2002. But before that, scientists thought it was alliinase, which is the enzyme that produces sulphenic acid, which was the tear producing culprit. And that was a shame because that’s what makes onions taste so good. And now that we know that LFS is to blame, who knows? Once we wait for these magical onions, there’s also remedies on the internet to prevent tears from this multilayered monstrosity. So to test them out, I’m gonna need some help. Let me introduce you to Preeti. She’s a scientist too. We’re going to decide to test out which remedy by using the age old methods of decision making – taking out a hat and to make sure we both get the same amount of exposure, we’re going to time it. Preeti, as a guest. Pick one more.
Preeti
I think I’ll get worse first with cutting the onion whilst holding your tongue to the roof of your mouth.
Maaria
Two minutes on timer. Preeti, please start chopping. So as well as looking fabulous while we chop the onions, what is this method actually supposed to do? This is supposed to give PSO, which is a gas given off when LFS reacts with sulphenic acid, a chance to interact with your saliva. It is therefore you don’t cry and sulphuric acid is produced in your mouth and in your eyes. Breathing through your mouth is also supposed to affect the stimulation of your olfactory nerves, which are up your nose. I’m not quite close to the [inaudible], so you don’t see like those there’s less chance of stimulating your tear ducts and you don’t cry. Preeti, how are you doing? Strawberry? How about for you?
Preeti
That was awful.
Maaria
Oh god! You’re crying. On a scale from one to five; one being “didn’t help at all” – five being “did the job”, how are you feeling?
Preeti
Gonna say 1. I’m crying and it’s stinging.
Maaria
So that’s a number 1. That doesn’t work.
So that’s my turn. My first one is cutting an onion whilst having a spoon in your mouth.
Preeti
Having a stainless steel spoon in your mouth is supposed to bind the PSO to the metal and therefore taking it away from your eyes and therefore no tears. How are you doing? How are you feeling?
Maaria
I’m feeling okay, a little bit stingy but there’s no tears. Yeah, but it’s really hard having the spoon in your mouth and a lot of saliva generated. I’ll probably give this one maybe a 3 midway.
Preeti
So I’m going to go next and I’ll be cutting an onion that has been soaking in water for about 20 minutes.
Maaria
Two minutes on the clock, get chopping. So why would soaking an onion in water help? Soaking an onion in water is supposed to draw out the sulphuric compounds from the surface of the onion unless it compounds mean PSOs are released so you don’t get any tears. So that’s the theory. How is it working?
Preeti
I mean a little bit stingy but actually no tears yet. It’s stinging my eyes but no tears. Just irritating to the eyes. I think I’ll give that a 4.
Maaria
Okay.
So my next one is cutting an onion that has been in refrigerator. So this onion has been in the fridge for about an hour so good long while.
Preeti
You ready?
Maaria
Ready steady.
Preeti
So cooling down onion is supposed to reduce activity of those pesky enzymes. This then slows down the production of the sulphuric compound and therefore there no tears.
Maaria
Seem to be winning at the moment. Yeah, magic science. Up the last minute, I got a little bit of a sting. I don’t really feel anything for. I would probably rate that a 4. Just got a little bit stingy at the end.
Preeti
And now I’m gonna cut the onion in these attractive ski googles.
Maaria
Gosh you look cool! Besides looking cool, what are the goggles actually doing? It’s pretty simple. The goggles are protecting your eyes. So PSO can’t catch them and no tears. sulphuric acid can get into therefore no tears they do what they say on the tin.
Preeti
So far so good. Stop your chopping. It was pretty good. It was pretty well. Just a little bit stingy. Physical barriers were working. I think I will give it a 4 as well.
Maaria
Final test we’re going to do is cutting an onion while chewing gum.
Preeti
This remedy is supposed to draw a PSO so it mixes with your saliva taking it away from your eyes. Tasty?
Maaria
Delicious combo so never want to have again.
Preeti
How are you feeling?
Maaria
That definitely stings you, haven’t got any tears yet, actually… Having onion-flavoured chewing gum is definitely not the way to go.
And we gonna flip a coin and see who loses and the loser gets to put their face over this lovely tub of onions that we chopped throughout the video for five whole…
Preeti
Heads
Maaria
Tails
Preeti
That means you. I’m enjoying it now.
Ready? Go!
Just breathe it in. All the oniony goodness.
Mutation. The tears, rising brimming up. It’s okay. We’re all here. 30 seconds to go.
Maaria
Oh my god. Well that definitely did the trick. That sting for nasal passages was somewhat wrong. So in the end, we found that these methods work to stop you bobbing whilst you cut onions.
Preeti
These methods on the other hand, are more of the old wives tale variety.
Maaria
They don’t really work. So now you know some painfree methods of preparing delightful root vegetable. No problem. If you enjoyed this video, give it a thumbs up and let me know what you wonder about in the comments below. All my social media links are in the description box. So check them out for daily updates on cool things that going on in the science world. And if you want to keep up to date on my videos, click on this onion to subscribe to my channel. Go do it. Alright guys, thanks for watching. Have a wonderful day.
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