Sincere tears, or crocodile tears?

If you have ever stepped into the kitchen, to help and assist with cooking, you will know the pain of chopping onions. Often, there are many memes coming up about the pain of tearing up while cooking with onions. Inevitably, there are several cuisines that require the fragrance and essence of the vegetable. Our chemistry tutor is more than happy to share about kitchen chemistry today! Essentially, everything happening around us revolves around science. It is indeed becoming important to understand what is the reason behind such occurrences. Onions are just common vegetables, but the chemistry behind is surprisingly uncommon. Famous scientists have discovered that, the moment a small part of a knife comes into contact with the onion, a series of reactions are triggered. As our chemistry tuition would have taught us how molecules are all around us, such stable molecules of onion tissues begin to become volatile gas. This gas further reacts with our eyes to form small amounts of sulfuric acid. We would have learnt in our lab sessions in school that coming into contact with sulfuric acid could cause irritation in skin. Similarly, this burning effect causes tears to form up, and therefore, we shed crocodile tears.

Is it that simple?

The process of acid formation is actually more complicated than it seems. Just like how the more we think about something, things get more difficult to understand, this process is more than it seems. Since the 1970s, Chemist Eric Block from the University of Albany in New York, has been working on this problem. The structure of one of the onion’s eye-irritating molecules contains a chemical called lachrymatory. Our chemistry tutor would usually advise that the structure of any molecule will show the position of different atoms that would form it up. The structure will further give us clues about how the molecule is being formed. His initial hypothesis was that a chemical reaction occurs only after an onion is being cut. However, chemical reactions usually require a catalyst to begin with. This is often described as an energy ‘bomb’ by our chemistry tutor. This enzyme to power up the start of the chemical reaction in onion is alliinase. This enzyme is popular amongst many plants, just like how the Korean BTS band is popular among many of us today. Garlic and Onions are two of such popular plants which help make some volatile chemicals giving these foods a certain aroma.

Last piece of the puzzle

Science is a gradual building process. There is always a reason behind everything happening. The reason why onions produce eye-irritating chemicals in the first place was to probably help the plant to defend itself from its predators. This chemical which hurts human eyes, might also possibly trigger pain in other organisms. Eventually, this makes the beauty of nature. Our chemistry tuition teaches students to appreciate the little things around, and link them to chemistry as close as possible. That’s what makes it interesting!

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