Onions lower blood cholesterol levels and are foods with excellent antioxidant effects. They are good for health and also enhance sweetness, making them an essential ingredient in many dishes. We explored the proper onion preparation and cooking methods to ensure you don't miss out on the benefits of onions.

◇ Only remove the brown outer shell

When washing and preparing onions, it is best to peel only the brown outer skin. This is because the transparent second layer of skin beneath the brown peel is rich in nutrients such as calcium and magnesium. In particular, onion skins contain 20 to 30 times more polyphenols and about four times more quercetin than the onion flesh. Polyphenols help convert active oxygen, which attacks normal cells in our body, into harmless substances. Quercetin plays a role in lowering blood cholesterol levels and aiding blood circulation. The nutrients in onions are more concentrated in the outer skins. If eating the skins is difficult, you can add whole onions with skins when boiling broth or dry and grind the skins into powder to consume.

◇ Slicing onions vertically helps.

It is best to cut onions vertically along the onion's fiber (fibrous tissue). This way, the onion's tissue cells are broken down, activating nutrients such as allicin. Sliced onions should be left at room temperature for about 15 to 30 minutes before cooking. When onions come into contact with oxygen, the sulfur compounds responsible for spiciness are converted into beneficial enzymes in the body. This process helps to boost metabolism and prevent blood clot formation.

◇ Roasting in oil enhances the sweetness

Stir-frying onions in oil can enhance nutrient absorption. Additionally, when onions are sautéed, moisture evaporates, intensifying their sweetness. In particular, some of the organic compounds responsible for the spiciness of onions decompose and transform into propyl mercaptan. Propyl mercaptan produces a sweetness 50 to 70 times stronger than sugar. Most of the nutrients in onions are not sensitive to heat, so even when stir-fried in oil, their nutritional components are not diminished.

Meanwhile, good onions feel heavy when touched, are firm and not soft. Also, the onion skin should be clear and well-dried. When selecting onions, it is best to choose ones that do not show sprouts, do not have a dark color, and have thin but not easily peelable skins.

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When cooking with onions

I try to remove only the brown outer skin as much as possible.

The brown part and the head part of the green onion

It also makes a great broth.