One common vegetable known as the "Vegetable Queen", some people also call it "heart stent". It is recognized as a medicinal vegetable——Onion.

What is onion?

Onion is a biennial herb of the genus Allium in the family of Liliaceae, also known as the bulb onion, round onion, Dutch onion, etc., consisting of leaves, stems, and roots. What we usually eat is the bulbous part of the stem - bulbs, that is, the onion head. Onions are native to Central Asia and the Mediterranean coast, and later passed through Europe to China, are important seasoning vegetables in East and West.

How is the nutrition?

There are three kinds of onions: white, yellow, and purple. White onions are tender, with higher moisture and sweetness, and more suitable for fresh food, barbecue, or stew. Yellow onions taste sweet and a bit spicy and can be eaten raw while purple and white mixed onions show more moisture, crispy texture, and spicy taste, suitable for frying to eat.

The protein, dietary fiber, and minerals such as calcium, phosphorus, potassium, sodium, magnesium, zinc, and iron of purple onions are higher than the other two onions, but the latter two are higher with carotenoids and vitamin C. In addition, purple onions contain strong antioxidant phytochemicals - anthocyanins, which are known as the cleaner of human skin, can protect the body from free radical damage and smooth the skin.

Based on their nutritional value, purple onions are more nutritious, mainly due to the higher content of allicin and quercetin which is quite beneficial.

Why onion is the heart stent in food?

Onion is common in our daily life. It has high dietary value and is known as the "Vegetable Queen" in European and American countries. Little-known is that onions are also called the "heart stent" in food due to the outstanding protection of the heart. Research shows that the organic sulfides in onions have an anti-thrombotic effect, help prevent platelet coagulation, and reduce cholesterol and triglyceride levels; its rich flavonoids have a strong antioxidant effect, and help prevent cardiovascular and cerebrovascular disease.

Why onion makes people cry?

Flavor substances are not present in intact, undamaged onion bulbs, only the precursor substance: S-alk(en)ylcysteine sulfoxides(ASCO). Because ASCO and the enzyme that catalyzes its decomposition, alliinase, are present in the cytoplasm and cytosol respectively, intact onions do not show their distinctive flavor.

Only when the bulb is cut or broken does the odorless, nonvolatile precursor ASCO contact with the enzyme alliinase and decompose under the action of alliinase to produce the characteristic flavor of the onion. The main product of the enzymatic reaction is hyposulfuric acid, of which unstable aryl hyposulfuric acid quickly convert to thioalanal-S-oxide, which is the lachrymatory component of onions. When it contacts with the eyes, it stimulates the nerve endings in the cornea of the eye, so the body orders the lacrimal gland to secrete tears through the nervous system.

Modern medical research has confirmed that the reason for the name of “dietary supplement” is closely related to the onion volatile oil with pungent odor. Many developed countries such as the US, Japan and Switzerland has listed onion oil as raw materials for anti-AIDS drugs.

Onion volatile oil is a mixture of organic vulcanized compounds and a variety of volatile oils from fresh onions, which is obtained by water-steam distillation or other methods, has a good biological activity, as well as onion unique pungent aroma and flavor, which is widely used in food, cosmetics, and medicine.

Tips

When you cut onions, the spicy stimulation will inevitably make you cry. Here are some tips to help you with that. First, put onions into cool water for 3-5 minutes before cutting, or you could also put them into the refrigerator for 10 minutes. It will reduce the activity of the enzyme alliinase greatly, thus reducing the production of lachrymatory substances.