The strange reason why onions make you cry—And ways to stop crying

[WORLD] Onions are a staple in kitchens worldwide, adding flavor and depth to countless dishes. However, the simple act of cutting an onion can turn even the most stoic chef into a teary-eyed mess. Have you ever wondered why onions make you cry? The answer lies in a fascinating interplay of chemistry and biology that occurs when we slice into this pungent vegetable.

The Chemical Culprit: Syn-Propanethial-S-Oxide

At the heart of the onion's tear-inducing power is a compound called syn-propanethial-S-oxide, also known as the lachrymatory factor. This volatile sulfur compound is responsible for the irritation we experience when cutting onions. But how does this chemical come into existence?

When we cut into an onion, we damage its cells, triggering a chain reaction. The onion's cells contain an enzyme called alliinase, which is normally separated from sulfur-containing amino acids. As we slice through the onion, these components mix, creating a cascade of chemical reactions.

The Onion's Defense Mechanism

Interestingly, the production of syn-propanethial-S-oxide is actually a defense mechanism evolved by onions to protect themselves from pests and animals. When an onion is damaged, whether by a knife or a hungry creature, it releases this irritating compound as a deterrent.

Dr. Josie Silvarole, a food scientist at the University of Kentucky, explains, "The onion is essentially trying to stop you from eating it. It's a defense mechanism that the plant has evolved over time to try to prevent damage from predators."

From Onion to Eyes: The Journey of Tears

Once released, syn-propanethial-S-oxide becomes airborne and makes its way to our eyes. Upon contact with the moisture on the surface of our eyes, it forms a mild sulfuric acid. This acid irritates the nerve endings in our eyes, triggering the production of tears as a reflex action to flush out the irritant.

The Role of Sulfur Compounds in Onions

Sulfur compounds play a crucial role in the onion's ability to make us cry. These compounds are not only responsible for the tear-inducing effect but also contribute to the onion's distinctive flavor and aroma. The amount of sulfur in an onion can vary depending on factors such as the variety of onion and growing conditions.

Health Benefits of Onions

Despite their tear-inducing tendencies, onions offer numerous health benefits that make them worth the temporary discomfort. Onions are rich in antioxidants, particularly a compound called allicin, which has been linked to various health benefits, including improved heart health and potential cancer-fighting properties.

Dr. Silvarole notes, "Onions are really good for you. They have a lot of different health benefits, including antioxidant and anti-inflammatory properties."

Tips to Reduce Onion Tears

While the chemical reaction that causes onion tears is a natural process, there are several strategies you can employ to minimize the waterworks while preparing this flavorful vegetable.

1. Chill the Onion Before Cutting

Placing your onion in the refrigerator or freezer for about 15 minutes before cutting can help reduce tear production. The cold temperature slows down the chemical reactions that produce syn-propanethial-S-oxide, resulting in fewer tears.

2. Use a Sharp Knife

A sharp knife can make a significant difference when cutting onions. A dull knife crushes more cells, releasing more of the irritating compounds. A sharp blade, on the other hand, cleanly slices through the onion, minimizing cell damage and reducing the amount of syn-propanethial-S-oxide released.

3. Improve Ventilation

Good airflow can help disperse the tear-inducing compounds before they reach your eyes. Try cutting onions near a fan or open window to reduce eye irritation.

4. Wear Onion Goggles

Specialized onion goggles are designed to create a seal around your eyes, preventing the irritating compounds from reaching them. While they might look a bit silly, they can be highly effective in reducing tears.

5. Cut Onions Under Water

Some chefs swear by cutting onions under running water or in a bowl of water. The water helps to wash away the irritating compounds before they can become airborne.

6. Use the Right Cutting Technique

The way you cut an onion can affect how much you cry. Try cutting the onion with the root end intact, as this part contains the highest concentration of sulfur compounds. By leaving it until last, you can minimize exposure to the tear-inducing chemicals.

Onion Varieties and Their Tear-Inducing Potential

Not all onions are created equal when it comes to their ability to make you cry. Some varieties, such as sweet onions like Vidalia or Walla Walla, tend to have lower sulfur content and may be less likely to induce tears. However, these milder onions often have a shorter shelf life compared to their more pungent counterparts.

Proper Onion Storage for Reduced Tears

How you store your onions can also impact their tear-inducing potential. Proper storage not only helps maintain the onion's quality but can also affect the intensity of its lachrymatory factor. Store onions in a cool, dry, and well-ventilated area to preserve their freshness and potentially reduce their tear-inducing effects.

Cooking with Onions: Minimizing Tears in the Kitchen

For those who love the flavor of onions but dread the preparation process, there are cooking techniques that can help. Sautéing or caramelizing onions can break down the compounds responsible for tears, resulting in a sweeter, milder flavor. Additionally, using pre-chopped frozen onions or onion powder can be alternatives for recipes where fresh onions aren't crucial.

Embracing the Onion: A Flavorful Journey

Despite the temporary discomfort they may cause, onions remain an indispensable ingredient in cuisines around the world. Their unique ability to add depth, sweetness, and complexity to dishes makes them worth the occasional tear. By understanding the science behind why onions make us cry and employing some of the techniques mentioned, we can continue to enjoy this versatile vegetable with minimal waterworks.

As Dr. Silvarole reminds us, "Don't let a few tears deter you from using onions in your cooking. Their flavor and health benefits far outweigh the temporary discomfort they might cause."

So the next time you find yourself tearing up over a cutting board, remember that you're witnessing a fascinating example of plant chemistry in action. With a little knowledge and a few tricks up your sleeve, you can master the art of onion preparation and unlock a world of culinary possibilities.