For centuries, This wonderful vegetable has been in use virtually in every aspect from science to medicine and most especially, for culinary uses.
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I'm here to tell you, a little about the Onion, and why it makes your eyes teary when cut.
THE ONION
The onion (Allium cepa L.), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium.
-Wikipedia
There are 11 known species of Onions;
Georgia Sweet
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Sweet Red
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Texas Super
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Sweet Texas
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Sweet White
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Yellow Granex (Vidalia)
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White Granex
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White Bermuda
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Walla Walla Sweet
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White Sweet Spanish
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Yellow Sweet Spanish
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Despite, this numerous known species, they all have one thing in common; "All species makes the eyes watery/teary, when cut"
Nutritional value per 100 g (3.5 oz)
Energy 166 kJ (40 kcal)
Carbohydrates 9.34 g
Sugars 4.24 g
Dietary fibre 1.7 g
Fat 0.1 g
Protein 1.1 g
Vitamins
Thiamine (B1) (4%) 0.046 mg
Riboflavin (B2) (2%) 0.027 mg
Niacin (B3) (1%) 0.116 mg
Pantothenic acid (B5) (2%) 0.123 mg
Vitamin B6 (9%) 0.12 mg
Folate (B9) (5%) 19 μg
Vitamin C (9%) 7.4 mg
Minerals
Calcium (2%) 23 mg
Iron (2%) 0.21 mg
Magnesium (3%) 10 mg
Manganese (6%) 0.129 mg
Phosphorus (4%) 29 mg
Potassium (3%) 146 mg
Zinc (2%) 0.17 mg
Other constituents
Water 89.11 g
Fluoride 1.1 µg
WHY DOES IT HURT/MAKE THE EYES TEARY
As it is widely known that the "Lacrimal gland" is the gland that secretes/produces tears in the eyes.
When an onion is cut, a volatile gas is released;
Syn-propanethial-S-oxide
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This gas stimulates nerves in the eye creating a stinging sensation. This gas is produced by a chain of reactions which serve as a defence mechanism: Cutting an onion causes damage to cells which releases enzymes called;
Alliinases
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These break down amino acid sulfoxides and generate sulfenic acids. A specific sulfenic acid, 1-propenesulfenic acid, is rapidly acted on by a second enzyme, the lacrimatory factor synthase, producing the syn-propanethial-S-oxide. This gas diffuses through the air and soon reaches the eyes, where it activates sensory neurons. Lacrimal glands therefore produce tears to dilute and flush out the irritant.
Over the years, there have been 'life hacks' on how to cut onions without getting the eyes irritated.
Like;Chewing gum, cutting under running water, Refrigeration few minutes,before cutting. They've all been proven true.
I hope,you've had a few to learn, Do upvote, resteem and comment.
Thank You