Sharp Knives Reduce Onion-Induced Tears By Limiting Droplet Spray, Study Finds (arxiv.org) 48
Cornell University researchers have solved a kitchen mystery by demonstrating that sharp knives produce fewer and slower-moving droplets when cutting onions compared to dull blades. The findings used high-speed cameras and particle tracking to analyze droplet formation during onion cutting at speeds up to 20,000 frames per second.
The team discovered that onion droplets form through a two-stage process: an initial violent ejection driven by internal pressure, followed by slower fragmentation of liquid streams in air. Blunter blades create up to 40 times more droplets because the onion's tough outer skin acts as a barrier, allowing the softer interior tissue to compress significantly before rupturing and releasing pressurized liquid.
The research reveals that droplets are ejected at speeds between 1 and 40 meters per second, with the fastest ones posing the greatest risk of reaching a cook's eyes. Beyond tear reduction, the study suggests sharp knives may also limit the spread of foodborne pathogens, since atomized droplets can carry bacteria like Salmonella from contaminated cutting boards.
The team discovered that onion droplets form through a two-stage process: an initial violent ejection driven by internal pressure, followed by slower fragmentation of liquid streams in air. Blunter blades create up to 40 times more droplets because the onion's tough outer skin acts as a barrier, allowing the softer interior tissue to compress significantly before rupturing and releasing pressurized liquid.
The research reveals that droplets are ejected at speeds between 1 and 40 meters per second, with the fastest ones posing the greatest risk of reaching a cook's eyes. Beyond tear reduction, the study suggests sharp knives may also limit the spread of foodborne pathogens, since atomized droplets can carry bacteria like Salmonella from contaminated cutting boards.
Interesting (Score:3, Interesting)
Re: Interesting (Score:2)
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I use two knives, one for fruits & vegetables and another for meats,
I would hope / assume that almost *everyone* does that...
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I use one for both, but crucially I only cut one type of meat, and I cut all the vegetables beforehand. Veg to meat is not a problem; meat to veg is, and raw meat to other raw meat is.
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Why, do you think that metal can't be sanitized? It's not even porous, so it won't exactly harbor bacteria after a thorough surface cleaning. Unless you're talking about the health of the blade itself.
If I'm cutting vegetables to cook with the meat I won't even wash it thoroughly in between. There's no point.
Re: Interesting (Score:4, Informative)
I wash mine.
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I hate the smell of syn-propanethial-S-oxide in the morning...
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I have one chefs knife that is sharp like a razor. I have a stainless steel bowl I make a sanitation solution in (one or two cap fulls of bleach) and throw in a clean small towel or two. The super sharp knife makes sure onions and the like don't squirt unneeded juice, and I can wipe off the blade between food types.
Kosher was created because people didn't know what germs are, and just knew that if you ate certain foods you were more likely to get sick, but didn't know why. And they didn't know that the pro
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I'm glad science finally proved that sharp knives are more efficient and make cleaner cuts than dull ones. I can finally sleep well tonight knowing 43 years of experience is finally backed by a large expensive study.
Where is DOGE?
Re: Funded By The Oblivious Obvious Company (Score:2)
I'm not sure why you're being downvoted. I absolutely agree with you. Sharper knife means less damage to cellular membranes, means less spillage, evaporation and all that, means less sulfuric acid forming in your eyes in contact.
We've known this for generations.
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Some people can't take a joke; even worse when they can't identify one.
Fuck 'em. Whatever.
Intuitive proof was enough for me (Score:2)
Making the edge progressively smaller will smash progressively less cellular structure.
Shape may be able to increase atmospheric mixing to maximize irritation potential, you'd have to experiment with that.
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Making the edge progressively smaller will smash progressively less cellular structure.
For some things toothy sharp knives are better. For other things (like onions) shaving sharp knives are better. It is good to have both, or at least know how to sharpen both, and to know which one to use for what.
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The substance isn't irritating itself. It's just if it comes into contact with water, it breaks apart, and one of the chemicals it produces is sulphuric acid. Of course, what happens is it drifts onto your eyes and the water-based tears covering it.
That's why "onion tears" are quite different from "emotional tears" or "regular tears"
Some places the people use full face respirators to protect the eyes if they're cutting large quantities of onions.
Duh (Score:2)
I was telling people this 30 years ago when I was shilling Cutco knives - it was one of their selling points.
and the old Slap Chop ? (Score:2)
and the old Slap Chop ?
chop onions like a man (Score:5, Funny)
I use the corner of a brick to chop my onions. Like a real man, I hold back the tears and swallow all my emotions.
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A real man just runs over the onion with his tractor then scoops up the remains, crying all the way back to the kitchen. Seriously, what dumbass funded this study?
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Bah. Tractors are for pussies. A real man crushes onions against his own forehead with his bare hands. Or pounds them into mush with his enormous manhood.
"Can you hammer a six-inch spike through a board with your penis?"
"Not right now."
"A girl's gotta have her standards."
Re:chop onions like a man (Score:4, Funny)
When Chuck Norris slices onions, it's the onions that cry.
How much did this study cost? (Score:2)
This is well known information and any professional chef could have told you this.
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This is well known information and any professional chef could have told you this.
But could they explain why and show evidence supporting their hypothesis?
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The reason why is pretty obvious, but I didn't get a grant to buy all the high speed cameras. I just have a kitchen at home.
Some extra "how" on the side (Score:2)
Of course this was already known. This is just the high speed camera version of proof. Everybody knows that getting shot in the face is a bad idea, but I still watched a ballistics jelly experiment demonstrating it. They aren't breaking new ground here... but it's still cool. I would call this worth watching.
Seriously? (Score:2)
Who paid for this?
Best not be a federal grant. If out of regular tuition or their enfoement, fine. Otherwise, wtf pid for such a useless study as chefs (and, samurai)already knew thisâ¦dull blades don't slice cleanly, they cut and crush.
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Nobody paid for it. At least nobody was charged directly. It's customary to cite grants funding research in any resulting papers, and in the case of *federal* grants it's *mandatory*. The authors simply thank the Cornell Center for Material Research for use of their rheometer and SEM. The equipment in the CCMR was purchased with NSF money, so I guess public money spent for whatever the wear-and-tear is for taking some rheometer measurements and SEM images.
If you look at the paper, it's not *really* an in
futher investigation reveals (Score:2)
Turns out a really sharp knife reduces tears caused by mothers-in-law.
Breathe through your mouth (Score:2)
I've been in the habit of breathing through my mouth whenever I cut onions.
When I do this, I don't have any problems with "onion tears".
Wear contact lenses (Score:2)
Irrespective of knife (FWIW, I use a Sabatier ceramic for onions - it's stupidly sharp), I find that when I wear glasses I get tears, but no tears when I'm wearing my contact lenses.
Re: Wear contact lenses (Score:1)
but (Score:2)
So what? Cutting onions properly reduces tears to zero. Been doing it for years.
contacts lenses (Score:2)
Contact lenses seem to make me impervious to onion tears.
Oh, Duh! (Score:2)
THAT'S what I've been doing wrong!
And here I've been using a sledgehammer, Gallagher-style, all this time!
Real Science? (Score:2)
It's not like cooks don't know this, since ... probably since the discovery of onions and sharp knives. I am no cook, and even I know that using a sharp knife helps. And it is absolutely logical why, if you think about it.
Great work! (Score:1)
This deserves the IgNoble prize.
What a discovery!! (Score:2)
So what's new? (Score:2)
Sharper knives cause less damage to cellular cells of any kind. The sulfuric acid forming in our eyes is just a consequence. We've known this for generations. Didn't need proving with an expensive study.
Common knowledge (Score:2)
This is common knowledge if you're not a scientist or a zoomer.
Here's some people talking about this "technique" 12 years ago on Reddit:
https://www.reddit.com/r/funny... [reddit.com]