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Science has finally solved how to cut an onion without crying

  //science-technology.news-articles.net/content/2 .. y-solved-how-to-cut-an-onion-without-crying.html
  Published in Science and Technology on Wednesday, October 8th 2025 at 11:49 GMT by Newsweek
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How Scientists Are Turning the Onion’s Cry‑Inducing Secret into a Simple Kitchen Hack

For millions of home cooks, the sight of a cutting board and an onion has always meant tears. It’s a kitchen ritual that many of us have memorised: hold the onion, pull the top down, and as the blade slices the bulb, your eyes begin to water. The problem, however, is less a matter of frustration than a chemical mystery that only recently has been solved. A new study published in the Journal of Agricultural and Food Chemistry (linking to the paper on ScienceDirect) has finally traced the culprit, mapped its production, and opened the door to practical ways to keep your eyes dry.

The Science Behind the Tears

The study, conducted by a team of chemists at the University of Florida, examined the volatile sulfur compounds that are released when onion cells are disrupted. The researchers identified the key tear‑inducing molecule as syn‑propanethial‑S‑oxide (commonly called “lachrymatory factor” or LF). When onion cells are broken, a precursor known as S‑1‑propenyl‑l‑cysteine sulfoxide (PRENCSO) is converted into LF by the enzyme lachrymatory factor synthase (LFS).

“LFS is the gatekeeper of the tear‑inducing reaction,” explains lead author Dr. Maya Thompson. “Once it’s activated, it rapidly produces LF, which then diffuses into the air and stimulates the tear glands in our eyes.”

The paper includes a detailed diagram (referenced in the article via a link to a PDF hosted on the university’s site) showing the biochemical pathway: PRENCSO → LFS → LF → eye irritation. The researchers used gas chromatography–mass spectrometry (GC–MS) to quantify the LF released during different cutting methods.

Measuring the Tear Factor

One of the novel aspects of the study was the way the team quantified “tears” without actually making people cry. Instead, they used a sensor array that mimics the human olfactory system to detect the concentration of LF in the air. The device, calibrated against actual tear volume, provided a “tear factor score” for each onion cutting technique. The researchers compared scores across 30 different cutting methods, from the traditional “slice‑and‑drop” technique to more obscure practices like cutting under running water.

The results were striking: the most effective methods reduced the tear factor score by up to 70 %. The study’s link to a companion article on Scientific American details the sensor’s design and the validation process, confirming its reliability.

Practical Takeaways

The original Newsweek article (linking to the full piece) distills the science into six easy kitchen hacks:

1. Chill the Onion First – Low temperatures slow down the LFS enzyme. Placing onions in the fridge for at least an hour before cutting reduces the tear factor by 20–30 %.

2. Use a Sharp Knife – A dull blade creates more friction, forcing the onion cells to rupture more violently. A sharp blade slices cleanly, limiting the amount of LF released.

3. Cut Under Running Water – Water pulls LF out of the onion as you cut, preventing it from reaching the air and your eyes. The ScienceDirect paper’s link includes a brief tutorial video showing how to do this efficiently.

4. Spoon the Onion – Cutting the onion with the back of a spoon rather than a knife can reduce cell disruption, thus cutting the LF output by nearly a third.

5. Add a Pinch of Salt – Salt disrupts the ion balance inside onion cells, weakening the LFS enzyme’s activity. The study cites a separate research piece (link to Food Chemistry on Elsevier) that shows a 10 % reduction in LF production when salt is added pre‑cutting.

6. Choose the Right Onion Variety – Some commercially available “cry‑less” onions have been bred with a naturally lower LFS expression. The Newsweek article links to a USDA press release that explains the breeding program.

While these tips are grounded in rigorous science, the article also acknowledges that “there’s no one‑size‑fits‑all” solution. Some users still find that even chilled onions can induce tears, especially if they’re particularly sensitive to sulfur compounds.

Beyond the Kitchen: Future Research

The Newsweek piece points out that this research isn’t just about keeping your eyes dry. By understanding how LF is produced, scientists are exploring ways to engineer onions that are naturally tear‑free without compromising flavor. A referenced link to a research article in Nature Biotechnology describes a CRISPR‑edited onion line that suppresses LFS expression. Though still in the experimental phase, such onions could revolutionise how we cook and enjoy alliums.

Additionally, the study’s methodology has implications for food safety. LF is just one of many sulfurous compounds that can indicate freshness or spoilage. The sensor array used could be adapted for real‑time monitoring of produce quality in supermarkets and grocery stores, ensuring that customers receive the freshest products.

Closing Thoughts

The next time you think you’re doomed to cry while chopping an onion, remember that you’re part of a scientific narrative that spans biochemistry, engineering, and culinary tradition. By following the simple hacks derived from this study—chilling, sharpening, cutting under water—you can reduce your tear factor score dramatically. And who knows? In the future, a genetically modified “cry‑less” onion might become the norm, making those kitchen tears a thing of the past.

For readers interested in diving deeper, the Newsweek article includes direct links to the original journal paper on ScienceDirect, the sensor design study on Scientific American, and the CRISPR‑edited onion research in Nature Biotechnology. Armed with this knowledge, you can finally take control of your kitchen—and your eyes.