Advanced Stir Fry Technique (Wok Hei)

Definition from Wikipedia on Chao (炒) and Bao () http://en.wikipedia.org/wiki/Stir_fry, both are stir fry techniques.  The Chinese definition is at http://zh.wikipedia.org/wiki/炒 for chao (炒) and http://zh.wikipedia.org/wiki/%E7%88%86%E7%82%92 for bao ().

PowerFlamer is great for these two classic stir-fry techniques of Chao (炒) and Bao (), both of which can provide the alluring smoky flavor of Wok Hei.

Chao technique is the familiar stir frying technique, and involves heating the wok to a high temperature, adding a small amount of oil, followed by spices, meats, vegetables, and liquid in succession. In bao technique, the iron or steel wok is heated much hotter, to a a dark red glow (approx 1200F of following table, see http://www.threeplanes.net/toolsteel.html for more detail), and the oil, seasonings and meats are added in rapid succession and rapidly tossed. Besides the high heat from the stove, cooking technique is extremely important for both Chao and Bao.

Wok Hei Colors

Other dishes like beef chow fun (http://en.wikipedia.org/wiki/Dry-fried_beef_with_hefen) traditionally have more wok hei, and experienced chefs will catch flames several times (example GongBaoChicken). The flavor is complex, and it is caused by a mixture of sooty compounds from the combustion of oil, caramelization of oxidized sugars, and Maillard reactions between amino acids (from the proteins in meats) and reactive carbonyl groups of sugar. These are similar to the chemical reactions which cause toast, or barbecued foods to have a rich taste.Wok Hei (Cantonese ) is defined at http://en.wikipedia.org/wiki/Wok_hei and can be caused by high heat cooking, and it is enhanced if you catch some flames inside the wok which tossing your ingredients. Too little flame, and the flavor can taste flat; too much flame and the flavor will be overwhelmingly sooty. Some dishes, like stir-fried greens benefit from one or two small bursts of flame.

Wok hei is related to the PowerFlamer’s flame (the temperature), the oil, and the metal (iron or steel or aluminum) of the wok itself.

Aluminum will melt at high temperatures, and only iron and steel are suitable for very high heat cooking. The material of the wok itself is important. Traditional Chinese woks are made of iron; modern woks are made of lighter metal or stainless steel. Many Chinese restaurants use iron woks, although iron woks will rust and is more difficult to clean (see article on this site about caring for and seasoning your wok); but both problems do not hinder the restaurant chefs because they use the wok every day.

Wok hei is complex to achieve, and it is often used as a measure of a Chinese chef’s skill. Besides practice and practice, here are some pointers that might help you:

1. Pre-heating time: For Bao technique and Wok hei, lengthen the time for the wok to pre-heat, so that the wok reaches a very high temperature just BEFORE you put in the oil, raw vegetable or meat. In general, the wok must be heated when the cooking oil in it starts to vaporize (blue vapors). To achieve even higher temperature, do not put in cooking oil when the wok pre-heats; pour in cold cooking oil just before you put in the raw food — this way, the oil won’t chemically decompose due to the high temperature.  (Also, different types of vegetable cooking oil, such as corn, canola, olive, peanut, have different vaporization temperature points.)

2. More cooking oil: In general, more oil is needed to for Bao technique and wok hei, than for Chao. The amount of oil must be carefully controlled; too much oil, it becomes “frying”; too little oil, you won’t get the Wok hei. The flame inside the wok arises because boiling water from your ingredients causes a spatter of fine oil droplets. That oil mixes with oxygen in the air, and catches on fire if you deliberately toss the wok so that the oil spatter comes in contact with the PowerFlamer flames. More oil tends to produce more flames. You can control this through your technique for tossing the wok, and mixing your ingredients. Usually flames will die down within 1-2 seconds.

3. Right amount of water moisture in the raw food. The water moisture is an important ingredient in Wok hei. Water moisture comes from the raw vegetables, and also from water left on vegetables after washing. Too much water moisture, and the food is soggy; too little, the food is dry and burned. This part is difficult to control, but you can experiment with the moisture control by letting the vegetable air-dry for varying amount of time before cooking.

4. Amount of the raw food (vegetable or meat). Good chefs are able to achieve Bao and Wok hei, because they do NOT cook too much food in the wok in one go — they prefer to cook a small amount. The smaller amount is important for quick stirring and for temperature control (for maintaining the high heat during stir frying) — think about heat-to-weight ratio (weight of the food). A light-weight wok (made of aluminum) is able to heat up fast but to retain LESS heat (once heated up); in that case, you need to decrease the amount of raw food for cooking with a light-weight wok. I suggest that you start experimenting with small amount of food (just enough for a small dish).

You can put out flames by covering a wok. NEVER throw water into a flaming wok to put out a fire.

Please try some of these, and tell us what you think. Happy cooking!

Some links on this subject (Wok hei, wok material, wok maintenance):

1.  Here’s the seasoning process as described by Ala Luke (Link to Youtube).

2. Wok in the street of Phnom Penh (Link to Youtube).

3. Learn about basic Chinese cooking equipment – wok, ladle (Link to Youtube).

4. Wikipedia article http://en.wikipedia.org/wiki/Wok_hei.