Onions – The Soul of Chinese Cooking

The onion (Allium cepa, Chinese „Yáng Cōng“, 洋葱) is the most-processed flavour-vegetable in the world – and one of the most under-appreciated. Behind billions of dishes, often invisible by the end, it is the onion that creates depth. In Chinese cuisine this is true twice over: no onion, no wok-sauce; no onion, no broth-base; no onion, no dimension. The ingredient overview of China Restaurant Yung would lose a central axis without onions.

In Traditional Chinese Medicine the onion is classified as warm (温) and pungent (辛) – it moves Qi, dispels Wind-Cold and has mucus-resolving properties. Modern biochemistry knows it above all as a source of quercetin, one of the most effective flavonoids in the plant kingdom. Michael Greger places onions in the cluster of daily-recommended Allium vegetables among the anti-oxidative cornerstones. [Greger HNTA, „Cellular Senescence“ Ch. 6]

ChinaYung Essence: The onion weeps as you cut it – and in return makes the whole dish happy.

Nutrient Profile at a Glance

Botanical family	Amaryllis / Allium family (Amaryllidaceae)
Flavour (TCM)	Pungent (辛), warm (温)
Meridian direction (TCM)	Lung (肺), Stomach (胃)
Key active compounds	Quercetin, allicin precursors, sulphur compounds, folate, vitamin C, chromium
Energy content	~ 40 kcal per 100 g (raw)
Note	Red onions additionally contain anthocyanins (blue/red pigments)
Quercetin content	~ 30–50 mg/100 g (raw, higher than nearly any other vegetable)

More on flavonoids and secondary plant compounds in our nutrient section.

Botany & Origin

The onion is one of the oldest cultivated plants of humanity – records from ancient Egypt reach back 5000 years. It originated in Central Asia and arrived in China via Persia and Arabia. The Chinese name „Yang Cong“ (洋葱) means literally „foreign Allium“ – a hint to its relatively late introduction to China compared to spring onions, which have been native to China since antiquity.

Botanically the onion (Allium cepa) is closely related to garlic (Allium sativum), spring onions (Allium fistulosum) and chives. The Allium family comprises over 900 species – all sharing the characteristic sulphur metabolism responsible for both the tear-inducing and aromatic effects.

Main Scientific Effects

1. Quercetin – broad-spectrum antioxidant shield: Onions are the richest dietary quercetin source in a typical Western produce basket. Quercetin inhibits inflammatory mediators, acts antihistaminically, and has shown anti-proliferative effects on various cell lines in laboratory studies. [Greger HNTA, „Cellular Senescence“ Ch. 6]
2. Cardiovascular effect: Regular onion consumption is associated in population studies with lower blood-pressure values and better cholesterol markers. Sulphur compounds inhibit platelet aggregation (blood-platelet clumping) – natural blood-thinning.
3. Prebiotic effect: Onions contain inulin and fructo-oligosaccharides (FOS) – prebiotics that selectively promote Bifidobacteria and Lactobacilli in the large intestine. For the gut microbiome similarly valuable as garlic.
4. Blood-sugar regulation: Chromium and quercetin improve insulin sensitivity. Studies show a moderate blood-sugar-lowering effect with regular consumption.
5. Antimicrobial properties: The onion’s sulphur compounds act against a range of bacteria and fungi – historically onion poultices were used in wound care.

Culinary Application – In the ChinaYung Kitchen

Onions appear at ChinaYung in nearly every dish as an aromatic base. Their role changes with cut and cooking time:

• Fine dice, sweated long: The base of sauces and broths. Slowly sweated in soy sauce and sesame oil, Maillard-roast aromatics emerge – the foundation of umami depth.
• Coarse cut, brief in the wok: As vegetable component in wok dishes where bite and sweetness should remain. Caramelised onions give natural sweetness without sugar.
• Raw as garnish: Thin rings over cold dishes – particularly red onions, whose anthocyanin colour and milder pungency provide contrast.
• In soups and stews: Hours of co-cooking releases a gentle sweetness – together with ginger and carrots the classic Chinese broth-trinity.

All dishes on our menu benefit in one way or another from onions.

Synergies & Bioavailability

• Onion + garlic: The classic Allium pair. Sweated together in fat, they potentiate their sulphur compounds and flavonoids. No overlap – complementarity.
• Onion + ginger: The aromatic trio onion-ginger-garlic is the Chinese counterpart of the Western „soffritto“ – an indispensable aromatic base.
• Quercetin + vitamin C: Vitamin C stabilises quercetin in the body and prolongs its effect. Broccoli as a side vegetable is the ideal combination.
• Raw > cooked for quercetin: Quercetin withstands cooking better than many other flavonoids, but raw onions contain roughly 20–30 % more than heavily cooked ones. Keep wok time short.

Preparation & Storage

Avoiding tears: Cool the onion for 15 min before cutting – colder onions release fewer volatile sulphur compounds. Alternatively cut under water or use a sharp knife (less cell destruction).

Cut forms: Brunoise (dice), julienne (strips), rings – depending on the dish. For sauces: very fine. For wok: medium-coarse. For soups: coarse, so they don’t disintegrate.

Caramelisation: Very low heat, plenty of time (30–45 min), no added sugar needed. The onion’s natural sugars become complex aromatics via the Maillard reaction. Worth the effort.

Storage: Whole onions dry, cool, dark and ventilated – no refrigerator (moisture causes mould). Cut onions wrapped in foil keep in the fridge 3–5 days. Keep away from potatoes: ethylene and moisture accelerate mutual spoilage.

Caution & Contraindications

• FODMAP sensitivity: Onions contain fructans (FODMAP carbohydrates) that can cause bloating and abdominal pain in irritable bowel syndrome (IBS). Long-cooked onions reduce FODMAP content slightly; for IBS-affected individuals spring onions (green parts only) are a more tolerable alternative.
• Breath odour: Sulphur compounds are exhaled through the lungs and skin. No health issue – but socially relevant. Parsley or ginger tea help.
• Interaction with blood thinners: With high onion consumption and concurrent use of anticoagulants (e.g. warfarin/Marcumar) the platelet-inhibiting effects may summate. Medical consultation recommended when on medication.

More on dietary interactions in our basics section.

Science & Tradition in Dialogue

The TCM use of onion to treat Wind-Cold colds and to resolve mucus aligns well with modern research: sulphur compounds do act as mucolytics and antimicrobials. Quercetin has antihistaminic effects that can ease cold symptoms.

What TCM has not formalised – but practises intuitively – is the prebiotic principle: the onion nourishes not only humans but also the gut microbiome. In long soups and broths the onion releases its inulin fibres into the liquid – these end up in the colon as food for beneficial bacteria. Simple and effective.

For deeper reading on Allium plants we recommend the monographs on garlic and spring onions from our ingredients overview.

Summary – Indispensable Depth

The onion creates depth. Without it, Chinese cooking would be a two-dimensional affair. Quercetin protects heart and cells, prebiotics feed the microbiome, sulphur compounds strengthen immune defence and vessels – all packed into a vegetable with almost no calories and available everywhere.

Related ingredients: garlic · spring onions · ginger · all ingredient monographs · health section.

FAQ

Are red or yellow onions healthier?
Red onions additionally contain anthocyanins and have somewhat more quercetin. Yellow onions are more heat-stable and more aromatic when cooked. For raw use: red. For wok and sauces: yellow or white.

Can you eat onions daily?
Yes – for most people without issue. For FODMAP-sensitive individuals, monitor daily and reduce amount if needed. More on our health-goal strategy.

Why do we cry when cutting onions?
Cutting brings alliin and the enzyme alliinase – stored in separate cell compartments – together; volatile propanethial-S-oxide forms and irritates the tear glands. Sharp knife + cool onion = less cell destruction = fewer tears.

Can I cook onion skins too?
Yes – the outer dry skins release quercetin and colour into broths. In Asian cuisine they are often co-cooked for stock bases, then strained out. No direct consumption of the skins.

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