I am sure I am not the only one who hated it anytime I have to chop vegetables whilst preparing my meals. The fight with the onions and the unpleasant experience that it brings is one that I have no pleasure in enduring. This vegetable that we mostly cannot do without have a way of punishing us anytime we chop it for our foods.
Onions ( Alluim cepa) belong to a group of vegetables classified as bulbs and has a globe shape with fibrous roots. The bulk of its consumable part is concentrated at the stem as the leaves dry out signifying its maturity. Onions are rich in antioxidants such as flavonoids, vitamins (vitamin C and B complex) and minerals such as potassium. It is good for cardiovascular health and also believed to have anti-cancer properties.
Onions are a central element when it comes to our diets as it is used in the preparation of stews, soups, gravies, sauces and also in salads and foods such as shawarma, burgers and our stir fries. Its unique aroma enriches the taste and flavor of foods when it used. It also adds to the bulk of the food as it contains fibers that help in increasing the volume of the food. Some people also eat it raw and others prefer it cooked or in their sauces. No matter the form in which you like it, you just cannot do without onion.
What happens when you cut onions?
The onion cells have the contents partitioned and marginalized in various compartments. When you cut onions, the cell walls are disrupted which causes its constituents to mix leading to formation of new products. Onions are good absorbers of sulfur and so absorbs a lot of sulfur from the soil which it uses in its metabolic activities such as synthesis of amino acids. Some of these sulfurs are stored in the cells of the onion.
When onion is cut , previously compartmentalized enzymes, lachrymatory-factor-synthase is released which reacts with the sulfur in the amino acids leading to the formation of sulfenic acids which later rearranges to form syn-propanethial-s-oxide a volatile gas which evaporates into your eyes due to the air current. Syn-propanethial-s-oxide is a lachrymatory agent meaning it induces tears when it gets in contact with the eye.
Upon reaching your eyes it dissolves in the watery medium and converts to sulfuric acid which reacts with the eye cells causing an irritation. The body as part of its defense mechanism stimulates your tear glands to produce tears which floods your eyes causing you to be all teary, with red eyes and sometimes have a runny nose.( Prabha, 2014)
Can this damage my eyes?
The feeling might be extremely irritating sometimes causing you to be unable to even open your eyes for a period of time. Sometimes the eye balls becomes extremely red and itchy but it is not dangerous to your eye health. Your eyes can withstand it and will get better.
How do I deal with long period of irritation?
Rinsing your eyes with water is a good start. The water dissolves the acid and flushes it out of your eyes.
Putting a cucumber slice over your eyes is also recommended. The cucumber absorbs the acid and helps your eyes to readjust.
Use eye drops. Eye drops can be used in situations where the eyes becomes too red. Some of these eye drops helps in the healing process and restores your eyesight back to health.
Cover your eyes with cotton wool soaked in aloe Vera. It helps to deal with the redness.
How do I prevent this?
Select the right variety of onion; some onions have been found to be have high sulfur contents whilst there are some with low sulfur contents too. Usually the bitter onions such as the white, red and the yellow varieties contain high amount of sulfur and are very reactive.
Despite their eye irritating nature, they are highly nutritious and should not be entirely avoided. The green, onions which is classified as sweet has low sulfur contents and are less likely to react. You can use these ones if you are highly reactive to onions. (Kato, 2016)
Cut properly; the manner in which the onion is cut also affects the intensity of their reactivity. Blunt knives damage lots of cells which leads to production of more syn-propanethial-s-oxides. Use sharp knives to cut your onions. This reduces the damage to the cells and keeps you protected.
Wear goggles; I agree no one wants to look like scientist in the lab whilst cooking in the kitchen. But if that will stop the discomfort, what is the harm in putting it on. Goggles protect your eyes and prevent the sulfenic acid from reaching your eyes. This keeps you safe and gives you the comfort that you deserve whilst displayi
ng your culinary arts. Fun fact cooking is chemistry so just be the scientist in your kitchen.
Chill your onions before cutting; water dissolves and reduces the concentration of compounds. Immersing your onions in a bowl of cold water causes the onion to absorb some of the water through osmosis reducing the concentration of the sulfur. The cold temperature also reduces the activities of the enzymes as they require an optimum temperature for maximum activity. But it is not advisable to freeze your onion since the freezing and thawing can lead to disruption of the cells causing structural loss to the onions and overall presentation and palatability of the onions.
Avoid storing your onions for long: Freshly stored onions causes less irritation than old ones. As time progresses the onions whilst being stored loses water which increases the concentration of the sulfur and produces more potent syn-propanethial-s-oxide. Using the onions early prevents the onions from being extra irritating and also reduces postharvest loss.
Use preprocessed onions; purchasing preprocessed onions such as onion powders, chopped onions and other forms of processed onion saves you the stress of cutting and also the painful and teary experience.
References
Kato, M., Masamura, N., Shono, J., Okamoto, D., Abe, T. and Imai, S., 2016. Production and characterization of tearless and non-pungent onion. Scientific Reports, 6(1), p.23779.
Prabha, J.L., 2014. Tear secretion-a short review. Journal of Pharmaceutical Sciences and Research, 6(3), p.155.
Zanteson, L., 2023. Onions--Worth the Cry!. Environmental Nutrition, 46(10), pp.8-9.
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